> ## Documentation Index
> Fetch the complete documentation index at: https://docs.ditto.live/llms.txt
> Use this file to discover all available pages before exploring further.

# Rust Release Notes

<Callout icon="circle-info" color="#3B82F6" iconType="regular">
  This content is for SDK V4. For the latest version, see the [V5 documentation](/sdk/latest).
</Callout>

<Update label="4.14.6" description="Release Date: Jul 02, 2026">
  ## 4.14.6 Common Changes

  <Icon icon="plus" iconType="solid" horizontal /> **Added**: a new timeout for WebSocket connect that is adjustable by system parameter transport\_websocket\_connect\_timeout. (#21866)

  <Icon icon="screwdriver-wrench" iconType="solid" horizontal /> **Fixed**: A bug in internal subscription bookkeeping caused long-connected Document Sync sessions to become disabled due to spurious capacity errors. (#SPO-1011)

  <Icon icon="screwdriver-wrench" iconType="solid" horizontal /> **Fixed**: a crash caused by an unhandled SIGPIPE signal on iOS and other Unix-based platforms. (#SPO-1037)

  <Icon icon="rotate-reverse" iconType="solid" horizontal /> **Changed**: The replication\_session\_request\_timeout\_secs and blob\_session\_request\_timeout\_secs system parameters are no longer functional; the timeouts have been removed. They are accepted for backwards compatibility but have no effect. (#SPO-869)
</Update>

<Update label="4.14.5" description="Release Date: Jul 02, 2026">
  SDK version `4.14.5` is known to have a regression. Use `4.14.6` instead.
</Update>

<Update label="4.14.4" description="Release Date: May 08, 2026">
  ## 4.14.4 Rust Specific Changes

  <Icon icon="plus" iconType="solid" horizontal /> **Added**: Method `Ditto::version()` to retrieve the SDK version as a String, replacing the callback-based `with_sdk_version()` method. (#SDKS-3011)

  <Icon icon="triangle-exclamation" iconType="solid" horizontal /> **Deprecated**: Enum `SortDirection` is deprecated and will be removed in SDK 5.0. (#SDKS-3011)

  <Icon icon="triangle-exclamation" iconType="solid" horizontal /> **Deprecated**: Enum `WriteStrategy` is deprecated and will be removed in SDK 5.0. (#SDKS-3011)

  <Icon icon="triangle-exclamation" iconType="solid" horizontal /> **Deprecated**: Method `Ditto::app_id()` is deprecated. Use `ditto.config()` for configuration access. (#SDKS-3011)

  <Icon icon="triangle-exclamation" iconType="solid" horizontal /> **Deprecated**: Method `Ditto::bus()` providing access to the experimental bus controller API is deprecated. The experimental bus module will be removed in SDK 5.0. (#SDKS-3011)

  <Icon icon="triangle-exclamation" iconType="solid" horizontal /> **Deprecated**: Method `Store::collection_names()` is deprecated. Use DQL queries instead. (#SDKS-3011)

  <Icon icon="triangle-exclamation" iconType="solid" horizontal /> **Deprecated**: The `experimental` module is deprecated and will be removed in SDK 5.0. (#SDKS-3011)

  <Icon icon="triangle-exclamation" iconType="solid" horizontal /> **Deprecated**: Method `Ditto::is_sync_active()` is deprecated. Use `ditto.sync().is_active()` instead. (#SDKS-3011)

  <Icon icon="triangle-exclamation" iconType="solid" horizontal /> **Deprecated**: The `observer` module is deprecated and will be removed in SDK 5.0. (#SDKS-3011)

  <Icon icon="triangle-exclamation" iconType="solid" horizontal /> **Deprecated**: All public types in the `store::query_builder` module are now deprecated, including `Collection`, `PendingCursorOperation`, `PendingIdSpecificOperation`, `Subscription`, `LiveQuery`, `LiveQueryEvent`, `LiveQueryMove`, `SingleDocumentLiveQueryEvent`, `PendingCollectionsOperation`, `CollectionsEvent`, `ScopedStore`, `ScopedCollection`, `BatchCursorOperation`, `BatchIdOperation`, `Action`, `WriteTransactionResult`, `DocChangeKind`, `UpdateResult`, `UpdateOp`, `DittoDocument`, `DittoMutDocument`, `MutableValue`, `DittoCounter`, `DittoCounterStoredFormat`, `DittoMutableCounter`, `DittoRegister`, `DittoRegisterStoredFormat`, and `DittoMutableRegister`. Use DQL queries instead. (#SDKS-3011)

  <Icon icon="triangle-exclamation" iconType="solid" horizontal /> **Deprecated**: Method `Ditto::root()` is deprecated. Use `ditto.absolute_persistence_directory()` instead. (#SDKS-3011)

  <Icon icon="triangle-exclamation" iconType="solid" horizontal /> **Deprecated**: Method `Ditto::start_sync()` is deprecated. Use `ditto.sync().start()` instead. (#SDKS-3011)

  <Icon icon="triangle-exclamation" iconType="solid" horizontal /> **Deprecated**: Method `Ditto::stop_sync()` is deprecated. Use `ditto.sync().stop()` instead. (#SDKS-3011)

  <Icon icon="triangle-exclamation" iconType="solid" horizontal /> **Deprecated**: Method `Ditto::with_sdk_version()` will be removed in SDK 5.0. Use `Ditto::version()` instead. (#SDKS-3011)

  <Icon icon="triangle-exclamation" iconType="solid" horizontal /> **Deprecated**: DittoBuilder, Identity trait and all Identity implementations. (#SPO-206)

  ## 4.14.4 Common Changes

  <Icon icon="rotate-reverse" iconType="solid" horizontal /> **Changed**: Increase the default limit of subscriptions queries displayed in \_\_small\_peer\_info from 16 to 32. (#21085)

  <Icon icon="screwdriver-wrench" iconType="solid" horizontal /> **Fixed**: A race condition where `fetchAttachment` could permanently fail to find locally-created attachments due to stale in-memory cache entries. (#21146)

  <Icon icon="rotate-reverse" iconType="solid" horizontal /> **Changed**: Write transaction diagnostic logs now include the blocking transaction's current operation, elapsed time, and queue depth. (#CORE-1449)

  <Icon icon="screwdriver-wrench" iconType="solid" horizontal /> **Fixed**: High latency when write transactions trigger evictions. (#CORE-1453)

  <Icon icon="rotate-reverse" iconType="solid" horizontal /> **Changed**: More information is logged at debug level around peer GC and eviction progress including what remote peers are being deleted. (#CORE-1455)

  **Performance**: Reduced redundant replication GC work during rapid eviction bursts by debouncing and coalescing compatible GC tasks. (#CORE-1466)

  <Icon icon="plus" iconType="solid" horizontal /> **Added**: Evictions are now logged with extra detail by SP and surfaced in the system:request\_history virtual collection. (#DS-1026)

  <Icon icon="plus" iconType="solid" horizontal /> **Added**: small\_peer\_info subscription queries now include arguments. (#DS-1027)

  <Icon icon="plus" iconType="solid" horizontal /> **Added**: system:system\_info subscription queries now include arguments; query location moved from key to value.query. (#DS-1027)

  <Icon icon="plus" iconType="solid" horizontal /> **Added**: Garbage collection for document sync sessions now imposes limits on the number of disconnected sessions that will be retained, even if the TTL is not exceeded. (#DS-1065)

  <Icon icon="screwdriver-wrench" iconType="solid" horizontal /> **Fixed**: v4 peers not reporting the SDK version of v5 peers in the presence viewer. (#SDKS-3090)

  <Icon icon="screwdriver-wrench" iconType="solid" horizontal /> **Fixed**: Transport watchdog no longer logs spurious "Address already in use" errors when restarting TCP/HTTP servers. The watchdog now waits for previous server tasks to fully exit and release their sockets before attempting to rebind ports, preventing EADDRINUSE races when servers are invalidated during e.g. app backgrounding. (#SPO-127)

  <Icon icon="screwdriver-wrench" iconType="solid" horizontal /> **Fixed**: Attachment garbage collection now removes empty shard directories, preventing inode leaks. (#SPO-158)

  <Icon icon="plus" iconType="solid" horizontal /> **Added**: Publish sync scopes in small peer info document. (#SPO-276)

  <Icon icon="rotate-reverse" iconType="solid" horizontal /> **Changed**: Ditto shutdown logging promoted to info level. (#SPO-626)

  <Icon icon="screwdriver-wrench" iconType="solid" horizontal /> **Fixed**: Bug which meant a Ditto starting log failed to be logged. (#SPO-626)
</Update>

<Update label="4.14.3" description="Release Date: Feb 19, 2026">
  ## 4.14.3 Common Changes

  <Icon icon="plus" iconType="solid" horizontal /> **Added**: The new `transport_tcp_connect_timeout` system parameter which shortcuts long platform-based TCP connection timeouts. (#20782)

  <Icon icon="screwdriver-wrench" iconType="solid" horizontal /> **Fixed**: Inconsistent internal hashing of Document IDs could cause failure to sync documents. (#DS-944)
</Update>

<Update label="4.14.2" description="Release Date: Feb 05, 2026">
  ## 4.14.2 Common Changes

  <Icon icon="screwdriver-wrench" iconType="solid" horizontal /> **Fixed**: A deadlock could occur where a device would fail to establish new P2P connections until restarted. (#20810)

  <Icon icon="rotate-reverse" iconType="solid" horizontal /> **Changed**: On-disk logs now make better use of available disk space by resuming writing to incomplete files. (#CORE-561)

  <Icon icon="screwdriver-wrench" iconType="solid" horizontal /> **Fixed**: premature connection cleanup causing duplicate connections. (#NETW-1021)

  <Icon icon="plus" iconType="solid" horizontal /> **Added**: Channel open retries and watchdog to tear down VirtualConnections that never open a channel, preventing resource exhaustion from stalled peers. (#NETW-1098)

  <Icon icon="screwdriver-wrench" iconType="solid" horizontal /> **Fixed**: queries in the legacy language might fail to surface documents with settable counters. (#QE-512)
</Update>

<Update label="4.14.1" description="Release Date: Jan 08, 2026">
  ## 4.14.1 Common Changes

  *No Specific Changes*
</Update>

<Update label="4.14.0" description="Release Date: Dec 18, 2025">
  # 4.14 - Major Data Sync Performance Improvements & DQL Settable Counter Type

  ## Major Data Sync Performance Improvements

  Ditto 4.14 delivers significant performance improvements for initial sync scenarios, achieved through intelligent batching of file system writes to minimize I/O overhead. Performance gains are visible across all document counts, with the most dramatic improvements at 100,000+ documents.

  ### Performance Impact

  Benchmarking shows substantial speed improvements during initial sync across the entire spectrum of document counts:

  #### Android (Kotlin) Performance - Results

  <img src="https://mintlify.s3.us-west-1.amazonaws.com/ditto-248bc0d1/images/v4/kotlin-initial-data-sync-4-13-vs-4-14.png" alt="Kotlin Initial Data Sync 4.13 vs 4.14" />

  | Document Count | 4.13.1  | 4.14.0  | Speed Improvement |
  | -------------- | ------- | ------- | ----------------- |
  | 100            | 5.73s   | 3.37s   | **1.7x faster**   |
  | 500            | 6.72s   | 3.62s   | **1.9x faster**   |
  | 1,000          | 7.14s   | 4.49s   | **1.6x faster**   |
  | 5,000          | 10.00s  | 6.04s   | **1.7x faster**   |
  | 10,000         | 12.98s  | 8.36s   | **1.6x faster**   |
  | 50,000         | 38.48s  | 22.23s  | **1.7x faster**   |
  | 100,000        | 82.02s  | 38.86s  | **2.1x faster**   |
  | 500,000        | 489.05s | 154.55s | **3.2x faster**   |
  | 1,000,000      | 789.35s | 328.98s | **2.4x faster**   |

  #### iOS (Swift) Performance - Results

  <img src="https://mintlify.s3.us-west-1.amazonaws.com/ditto-248bc0d1/images/v4/swift-initial-data-sync-4-13-vs-4-14.png" alt="Swift Initial Data Sync 4.13 vs 4.14" />

  | Document Count | 4.13.1  | 4.14.0  | Speed Improvement |
  | -------------- | ------- | ------- | ----------------- |
  | 100            | 2.81s   | 2.84s   | \~1x              |
  | 500            | 3.11s   | 3.09s   | \~1x              |
  | 1,000          | 3.26s   | 3.34s   | \~1x              |
  | 5,000          | 4.19s   | 3.88s   | \~1x              |
  | 10,000         | 5.03s   | 4.79s   | \~1x              |
  | 50,000         | 12.28s  | 8.74s   | **1.4x faster**   |
  | 100,000        | 22.14s  | 13.50s  | **1.6x faster**   |
  | 500,000        | 105.47s | 56.88s  | **1.9x faster**   |
  | 1,000,000      | 216.47s | 116.60s | **1.9x faster**   |

  **Key findings:**

  * **Android shows improvements at nearly all document counts**, ranging from 1.6x to 3.2x faster
  * **iOS shows the greatest improvements at 50,000+ documents**, reaching up to 1.9x faster
  * Performance benefits scale with document count, with the most dramatic improvements at 100,000+ documents

  ### What Changed

  Previous versions of Ditto wrote document updates to disk more frequently, resulting in significant I/O overhead when processing large volumes of documents during initial sync. Version 4.14 introduces intelligent write batching that:

  * **Reduces file system operations**: Groups multiple document writes into batched operations
  * **Optimizes I/O patterns**: Minimizes expensive disk seeks and flushes
  * **Maintains data integrity**: Ensures consistency guarantees while improving throughput
  * **Scales with document count**: Performance benefits increase with larger datasets

  ### When This Helps

  This optimization is particularly beneficial for:

  * Initial sync of large datasets (50,000+ documents)
  * Onboarding new devices to existing mesh networks with substantial data
  * Bulk data imports and migrations
  * Scenarios where mobile devices sync large catalogs or inventory systems

  ### Testing Methodology

  Performance benchmarks were conducted using a standardized dataset:

  * Document size: \< 1 KB (representing typical production data patterns)
  * All documents in a single collection
  * Test start: when `startSync()` is called
  * Test completion: when observer with `COUNT` statement fires with expected document count
  * Document count controlled via subscription to subset of size N
  * 15 runs per configuration with median values reported
  * Application and database reset between runs
  * Test configurations: 100, 500, 1K, 5K, 10K, 50K, 100K, 500K, 1M documents
  * Test devices: Samsung Galaxy S22 (Android) and iPhone 15 (iOS), both physical devices

  <Note>
    These results provide a general baseline. Actual performance will vary based on your specific data patterns, document sizes, network conditions, and device characteristics. We recommend validating performance against your own use cases.
  </Note>

  ## DQL Settable Counter Type

  Ditto 4.14 introduces `COUNTER`, a new CRDT type that extends the capabilities of the legacy `PN_COUNTER` with the ability to explicitly set counter values. While maintaining the same conflict-free increment and decrement operations, settable counters add a powerful `RESTART` operation that uses last-write-wins semantics.

  ### What's New

  The `COUNTER` type provides three operations:

  * **INCREMENT BY**: Add or subtract integer values from the counter (same as PN\_COUNTER)
  * **RESTART WITH**: Explicitly set the counter to a specific integer value using last-write-wins semantics
  * **RESTART**: Reset the counter to zero

  This makes counters ideal for scenarios requiring both distributed counting and periodic resets, such as:

  * Inventory counts that need recalibration when receiving shipments
  * Like/vote counts with administrative reset capabilities
  * Session or usage metrics that require initialization to specific values

  ### Usage

  Increment a counter:

  ```sql theme={null} theme={null} theme={null} theme={null} theme={null} theme={null}
  UPDATE COLLECTION products (stock_count COUNTER)
  APPLY stock_count INCREMENT BY 5
  WHERE _id = '123'
  ```

  Set counter to a specific value:

  ```sql theme={null} theme={null} theme={null} theme={null} theme={null} theme={null}
  UPDATE COLLECTION products (stock_count COUNTER)
  APPLY stock_count RESTART WITH 100
  WHERE _id = '123'
  ```

  Reset counter to zero:

  ```sql theme={null} theme={null} theme={null} theme={null} theme={null} theme={null}
  UPDATE COLLECTION products (stock_count COUNTER)
  APPLY stock_count RESTART
  WHERE _id = '123'
  ```

  ### Migration from PN\_COUNTER

  The `PN_COUNTER` type remains available for backward compatibility but is now considered legacy. For new implementations, use `COUNTER` to take advantage of the set and reset capabilities.

  If you have existing applications using `PN_COUNTER` and want to migrate to `COUNTER`, please contact our customer support team for guidance, as migrating between CRDT types requires careful planning.

  ## Additional Improvements

  ### Reliability & Error Handling

  * **Enhanced error recovery**: Additional recovery mechanisms for document deserialization errors, reducing potential crashes and data loss scenarios
  * **Improved diagnostics**: More detailed logging when peers receive data that cannot be deserialized due to hash mismatches, making issues easier to troubleshoot

  ### Bug Fixes & Stability

  * **Fixed**: DQL SELECT queries on indexed collections could deadlock when executed in an explicit transaction
  * **Fixed**: Index path query plans now consistently preserve document IDs across runs
  * **Documentation**: Corrected on-disk logger retention documentation (actual retention is 15 days, not 3 days)

  ## 4.14.0 Full Change Log

  <AccordionGroup>
    <Accordion title="Common Changes">
      **Performance**: Improved the underlying representation of Ditto documents for better performance. (feat(crdt): Improve in-memory format for CRDT documents, introduce feature flag for rkyv-encoded documents #17509)

      **Performance**: Document synchronization between peers now batches updates more efficiently, reducing processing time for large document sets. (Batching pt 4: Sync engine batches document diffs and document metadata #19273)

      <Icon icon="rotate-reverse" iconType="solid" horizontal /> **Changed**: More information is logged when a Ditto peer receives data that it cannot deserialize due to a hash mismatch. (#CORE-897)

      <Icon icon="rotate-reverse" iconType="solid" horizontal /> **Changed**: We now make an additional attempt to recover from some kinds of document deserialization errors, which may reduce errors or crashes due to deserialization. (#CORE-916)

      <Icon icon="rotate-reverse" iconType="solid" horizontal /> **Changed**: Document sync protocol now supports rkyv-encoded diffs, for more efficient initial synchronization. (#DS-531)

      <Icon icon="screwdriver-wrench" iconType="solid" horizontal /> **Fixed**: DQL SELECT queries on indexed collections could deadlock if executed in an explicit transaction. (#DS-648)

      <Icon icon="plus" iconType="solid" horizontal /> **Added**: COUNTER data type and APPLY clause syntax in UPDATE statements for settable COUNTER field modifications. (#QE-426)

      <Icon icon="screwdriver-wrench" iconType="solid" horizontal /> **Fixed**: Make sure that index path query plan preserve document ids across runs. (#QE-429)

      <Icon icon="screwdriver-wrench" iconType="solid" horizontal /> **Fixed**: Documentation for on-disk logger incorrectly stated logs are retained for 3 days; actual retention is 15 days. (#SDKS-1726)
    </Accordion>
  </AccordionGroup>
</Update>

<Update label="4.13.4" description="Release Date: May 08, 2026">
  ## 4.13.4 Common Changes

  **Performance**: Disk usage monitor now runs on a dedicated thread, reducing blocking operations that might impact performance. (#20191)

  <Icon icon="screwdriver-wrench" iconType="solid" horizontal /> **Fixed**: A deadlock could occur where a device would fail to establish new P2P connections until restarted. (#20810)

  <Icon icon="rotate-reverse" iconType="solid" horizontal /> **Changed**: Increase the default limit of subscriptions queries displayed in \_\_small\_peer\_info from 16 to 32. (#21085)

  <Icon icon="screwdriver-wrench" iconType="solid" horizontal /> **Fixed**: A race condition where `fetchAttachment` could permanently fail to find locally-created attachments due to stale in-memory cache entries. (#21146)

  <Icon icon="plus" iconType="solid" horizontal /> **Added**: The thread ID is now included in small peer console logs. (#CORE-1201)

  <Icon icon="rotate-reverse" iconType="solid" horizontal /> **Changed**: Query engine operator execution logs now identify which operator is being executed. (#CORE-1266)

  <Icon icon="plus" iconType="solid" horizontal /> **Added**: The number of tokio worker and/or blocking threads can now be configured by setting the `DITTO_TOKIO_WORKER_THREADS` and `DITTO_TOKIO_BLOCKING_THREADS` environment variables. (#CORE-1273)

  **Performance**: Store observer no longer re-queries unrelated collections when writes occur. (#CORE-1389)

  **Performance**: Observers using a single ID equality builder query now shortcut all query execution and get the document directly in constant time. (#CORE-1433)

  <Icon icon="rotate-reverse" iconType="solid" horizontal /> **Changed**: Write transaction diagnostic logs now include the blocking transaction's current operation, elapsed time, and queue depth. (#CORE-1449)

  <Icon icon="screwdriver-wrench" iconType="solid" horizontal /> **Fixed**: High latency when write transactions trigger evictions. (#CORE-1453)

  <Icon icon="rotate-reverse" iconType="solid" horizontal /> **Changed**: More information is logged at debug level around peer GC and eviction progress including what remote peers are being deleted. (#CORE-1455)

  **Performance**: Reduced redundant replication GC work during rapid eviction bursts by debouncing and coalescing compatible GC tasks. (#CORE-1466)

  <Icon icon="rotate-reverse" iconType="solid" horizontal /> **Changed**: More information is logged when a Ditto peer receives data that it cannot deserialize due to a hash mismatch. (#CORE-897)

  <Icon icon="rotate-reverse" iconType="solid" horizontal /> **Changed**: We now make an additional attempt to recover from some kinds of document deserialization errors, which may reduce errors or crashes due to deserialization. (#CORE-916)

  <Icon icon="plus" iconType="solid" horizontal /> **Added**: Evictions are now logged with extra detail by SP and surfaced in the system:request\_history virtual collection. (#DS-1026)

  <Icon icon="plus" iconType="solid" horizontal /> **Added**: small\_peer\_info subscription queries now include arguments. (#DS-1027)

  <Icon icon="plus" iconType="solid" horizontal /> **Added**: system:system\_info subscription queries now include arguments; query location moved from key to value.query. (#DS-1027)

  <Icon icon="plus" iconType="solid" horizontal /> **Added**: Garbage collection for document sync sessions now imposes limits on the number of disconnected sessions that will be retained, even if the TTL is not exceeded. (#DS-1065)

  <Icon icon="screwdriver-wrench" iconType="solid" horizontal /> **Fixed**: premature connection cleanup causing duplicate connections. (#NETW-1021)

  <Icon icon="plus" iconType="solid" horizontal /> **Added**: Channel open retries and watchdog to tear down VirtualConnections that never open a channel, preventing resource exhaustion from stalled peers. (#NETW-1098)

  <Icon icon="plus" iconType="solid" horizontal /> **Added**: Automatic generation of USE IDS clause from \_id equality predicates when possible. (#QE-313)

  <Icon icon="plus" iconType="solid" horizontal /> **Added**: Periodic dumping of the Query Engine system:request\_history cache to the Ditto log for debugging purposes. (#QE-583)

  <Icon icon="rotate-reverse" iconType="solid" horizontal /> **Changed**: Diff scans are now enabled by default for observer queries that contain `ORDER BY` clauses. (#QE-729)

  <Icon icon="screwdriver-wrench" iconType="solid" horizontal /> **Fixed**: v4 peers not reporting the SDK version of v5 peers in the presence viewer. (#SDKS-3089)

  <Icon icon="plus" iconType="solid" horizontal /> **Added**: Publish sync scopes in small peer info document. (#SPO-276)

  <Icon icon="rotate-reverse" iconType="solid" horizontal /> **Changed**: Ditto shutdown logging promoted to info level. (#SPO-626)

  <Icon icon="screwdriver-wrench" iconType="solid" horizontal /> **Fixed**: Bug which meant a Ditto starting log failed to be logged. (#SPO-626)
</Update>

<Update label="4.13.3" description="Release Date: Jan 26, 2026">
  ## 4.13.3 Common Changes

  <Icon icon="screwdriver-wrench" iconType="solid" horizontal /> **Fixed**: Connection manager now correctly cleans up orphaned connecting state when tasks are cancelled during shutdown (e.g., during auth refresh), preventing "Already connecting" errors on reconnection. (#20377)

  <Icon icon="screwdriver-wrench" iconType="solid" horizontal /> **Fixed**: queries in the legacy language might fail to surface documents with settable counters. (#QE-512)
</Update>

<Update label="4.13.2" description="Release Date: Dec 23, 2025">
  ## 4.13.2 Common Changes

  <Icon icon="rotate-reverse" iconType="solid" horizontal /> **Changed**: On-disk logs now make better use of available disk space by resuming writing to incomplete files. (#CORE-561)

  <Icon icon="screwdriver-wrench" iconType="solid" horizontal /> **Fixed**: DQL queries using indexes could yield wrong results upon document deletion. (#DS-851)

  <Icon icon="screwdriver-wrench" iconType="solid" horizontal /> **Fixed**: When another peer crashes, Ditto will stop attempting to connect to it in under 15 seconds. Previously, connection attempts would occur for up to 75 minutes at 5 second intervals. (#NETW-856)
</Update>

<Update label="4.13.1" description="Release Date: Nov 26, 2025">
  ## 4.13.1 Common Changes

  <Icon icon="screwdriver-wrench" iconType="solid" horizontal /> **Fixed**: DQL SELECT queries on indexed collections could deadlock if executed in an explicit transaction. (#DS-648)

  <Icon icon="screwdriver-wrench" iconType="solid" horizontal /> **Fixed**: Documentation for on-disk logger incorrectly stated logs are retained for 3 days; actual retention is 15 days. (#SDKS-1726)
</Update>

<Update label="4.13.0" description="Release Date: Nov 10, 2025">
  ## 4.13 - DQL Index Enhancements, Observability & Performance

  ## DQL INDEX Support for Union & Intersect Scans

  Ditto 4.13 introduces advanced index utilization for complex query predicates, enabling significant performance improvements for local queries and observer registrations.

  ### What's Available

  The query optimizer can now leverage indexes when evaluating queries with `OR`, `IN`, and `AND` operators through union and intersect scans:

  * **Union Scans**: When using `OR` or `IN` operators, the query engine can now use multiple indexes simultaneously, combining results from each index scan. For example, a query like `WHERE status = 'active' OR priority = 'high'` can use separate indexes on both `status` and `priority` fields.

  * **Intersect Scans**: For queries with multiple `AND` conditions, the engine can use multiple indexes and intersect their results, efficiently narrowing down matches. For example, `WHERE category = 'urgent' AND assignee = 'user123'` can leverage indexes on both fields.

  ### Performance Impact

  These optimizations can dramatically reduce query execution time for complex predicates, especially on large datasets. Instead of scanning entire collections, Ditto now uses indexes to quickly locate relevant documents.

  **Query Selectivity Matters**

  The performance improvement from these index optimizations is inversely related to the selectivity of your query—that is, the percentage of documents returned:

  * **Highly selective queries** (returning a small percentage of documents) see the most dramatic improvements. For example, a query that returns only 10% of a collection can be approximately 90% faster, as the index allows skipping the other 90% of documents entirely.
  * **Less selective queries** (returning a large percentage of documents) benefit less from indexes, since most documents still need to be examined.

  This relationship holds true for both union and intersect scans. Indexes work best when they can efficiently eliminate large portions of the collection from consideration.

  ### Usage Example

  Here's how union scans work in practice. First, create indexes on the fields you'll query:

  ```sql theme={null} theme={null} theme={null} theme={null} theme={null} theme={null}
  CREATE INDEX movies_runtime ON movies (runtime)
  CREATE INDEX movies_year ON movies (_id.year)
  ```

  Now run a query with an `OR` condition and use `EXPLAIN` to see the query plan:

  ```sql theme={null} theme={null} theme={null} theme={null} theme={null} theme={null}
  EXPLAIN SELECT * FROM movies WHERE runtime > 200 OR _id.year = 2000
  ```

  The query plan shows a `unionScan` operator that leverages both indexes:

  ```json title="EXPLAIN Result" expandable theme={null} theme={null} theme={null} theme={null} theme={null} theme={null}
  {
    "plan": {
      "#operator": "sequence",
      "children": [
        {
          "#operator": "unionScan",
          "children": [
            {
              "#operator": "indexScan",
              "collection": "movies",
              "datasource": "default",
              "desc": {
                "index": "movies_runtime",
                "spans": [
                  {
                    "index_key": {
                      "direction": "asc",
                      "include_missing": true,
                      "key": ["runtime"]
                    },
                    "range": {
                      "low": {
                        "included": false,
                        "value": 200
                      }
                    }
                  }
                ]
              }
            },
            {
              "#operator": "indexScan",
              "collection": "movies",
              "datasource": "default",
              "desc": {
                "index": "movies_year",
                "spans": [
                  {
                    "index_key": {
                      "direction": "asc",
                      "include_missing": true,
                      "key": ["_id", "year"]
                    },
                    "range": {
                      "high": {
                        "included": true,
                        "value": 2000
                      },
                      "low": {
                        "included": true,
                        "value": 2000
                      }
                    }
                  }
                ]
              }
            }
          ]
        },
        {
          "#operator": "fetch",
          "collection": "movies",
          "datasource": "default"
        },
        {
          "#operator": "filter",
          "condition": "((`runtime` > 200) OR (`_id`.`year` = 2000))"
        }
      ]
    }
  }
  ```

  The `unionScan` operator combines results from both `indexScan` operations—one scanning the `movies_runtime` index for documents with `runtime > 200`, and another scanning the `movies_year` index for documents where `_id.year = 2000`. This is significantly faster than scanning the entire collection.

  ### Scope & Limitations

  **This optimization applies to:**

  * Local DQL queries (`store.execute(...)`)
  * Observer registrations (`store.registerObserver(...)`)

  **This does NOT apply to:**

  * Sync subscriptions (which use a different evaluation mechanism)

  Sync subscriptions continue to work as before and are not affected by these local query optimizations.

  ## Data Sync Performance Improvements

  Ditto 4.13 includes significant optimizations for peer-to-peer sync reconnection scenarios, particularly when peers have accumulated changes while disconnected.

  ### Intelligent Session Resync

  When two previously synced peers reconnect after a period of disconnection, Ditto now intelligently detects when a full session resync (summary re-exchange) is more efficient than sending incremental updates. This avoids transmitting large, redundant diff-bearing updates that can slow down the sync process.

  **Key improvements:**

  * **Backlog-based detection**: The sync engine now tracks the size of pending changes (diff backlog) and automatically triggers session resync when the backlog exceeds a configurable threshold
  * **Faster reconnection**: By requesting a fresh session basis instead of sending accumulated diffs, peers can resynchronize more efficiently when they've been apart for extended periods
  * **Reduced redundant data transfer**: Eliminates unnecessary transmission of large update files containing redundant document changes
  * **Configurable threshold**: A new system parameter allows tuning when session resync should be triggered based on your application's sync patterns

  **When this helps:**

  This optimization is particularly beneficial in scenarios where:

  * Mobile devices reconnect after extended offline periods
  * Network interruptions cause peers to accumulate substantial local changes
  * Peers with large datasets reconnect after diverging significantly

  The result is faster sync completion times and reduced bandwidth usage during reconnection, especially noticeable when the document store has accumulated many changes during disconnection.

  ## New System Collection: `system:system_info`

  Ditto 4.13 introduces a new read-only system collection `system:system_info` that provides diagnostic and observability data about your Ditto instance. This collection logs key-value pairs with timestamps, allowing you to query runtime information, configuration, and performance metrics.

  ### What's Available

  The `system:system_info` collection tracks various categories of information:

  <AccordionGroup>
    <Accordion title="SDK Metadata">
      SDK version, commit hash, language, and platform

      ```json theme={null} theme={null} theme={null} theme={null} theme={null} theme={null}
      {
        "key": "ditto_sdk_version",
        "namespace": "core",
        "timestamp": 1762469332,
        "value": "4.13.0-rc.2"
      }
      ```

      ```json theme={null} theme={null} theme={null} theme={null} theme={null} theme={null}
      {
        "key": "ditto_sdk_commit",
        "namespace": "core",
        "timestamp": 1762469332,
        "value": "ca86b11de2"
      }
      ```

      ```json theme={null} theme={null} theme={null} theme={null} theme={null} theme={null}
      {
        "key": "ditto_sdk_language",
        "namespace": "core",
        "timestamp": 1762469332,
        "value": "JavaScript"
      }
      ```

      ```json theme={null} theme={null} theme={null} theme={null} theme={null} theme={null}
      {
        "key": "ditto_sdk_platform",
        "namespace": "core",
        "timestamp": 1762469332,
        "value": "macOS"
      }
      ```
    </Accordion>

    <Accordion title="Filesystem Metrics">
      Total device storage and available space, plus storage usage broken down by component (store, attachments, replication, auth)

      ```json theme={null} theme={null} theme={null} theme={null} theme={null} theme={null}
      {
        "key": "fs_device_available",
        "namespace": "core",
        "timestamp": 1762469347,
        "value": 370601351103
      }
      ```

      ```json theme={null} theme={null} theme={null} theme={null} theme={null} theme={null}
      {
        "key": "fs_device_total",
        "namespace": "core",
        "timestamp": 1762469347,
        "value": 994662584320
      }
      ```

      ```json theme={null} theme={null} theme={null} theme={null} theme={null} theme={null}
      {
        "key": "fs_usage_store",
        "namespace": "core",
        "timestamp": 1762469347,
        "value": 1225401728
      }
      ```

      ```json theme={null} theme={null} theme={null} theme={null} theme={null} theme={null}
      {
        "key": "fs_usage_attachment",
        "namespace": "core",
        "timestamp": 1762469347,
        "value": 4861774
      }
      ```

      ```json theme={null} theme={null} theme={null} theme={null} theme={null} theme={null}
      {
        "key": "fs_usage_replication",
        "namespace": "core",
        "timestamp": 1762469347,
        "value": 52129130
      }
      ```

      ```json theme={null} theme={null} theme={null} theme={null} theme={null} theme={null}
      {
        "key": "fs_usage_auth",
        "namespace": "core",
        "timestamp": 1762469347,
        "value": 8649
      }
      ```

      ```json theme={null} theme={null} theme={null} theme={null} theme={null} theme={null}
      {
        "key": "fs_usage_total",
        "namespace": "core",
        "timestamp": 1762469347,
        "value": 1300317779
      }
      ```
    </Accordion>

    <Accordion title="Transport Configuration">
      Complete snapshot of enabled transports and their settings, connection endpoints (WebSocket URLs, TCP servers), and peer-to-peer transport settings (Bluetooth LE, LAN, AWDL, etc.)

      ```json theme={null} theme={null} theme={null} theme={null} theme={null} theme={null}
      {
        "key": "transport_config",
        "namespace": "core",
        "timestamp": 1762468011,
        "value": {
          "peer_to_peer": {
            "bluetooth_le": { "enabled": true },
            "lan": { "enabled": true, "mdns_enabled": true }
          }
        }
      }
      ```
    </Accordion>

    <Accordion title="System Parameters">
      Non-default configuration parameters and collection sync scopes

      ```json theme={null} theme={null} theme={null} theme={null} theme={null} theme={null}
      {
        "key": "non_default_system_parameter[dql_strict_mode]",
        "namespace": "core",
        "timestamp": 1762468011,
        "value": false
      }
      ```

      ```json theme={null} theme={null} theme={null} theme={null} theme={null} theme={null}
      {
        "key": "non_default_system_parameter[user_collection_sync_scopes]",
        "namespace": "core",
        "timestamp": 1762468011,
        "value": {
          "benchmark_baselines": "LocalPeerOnly",
          "movies": "LocalPeerOnly"
        }
      }
      ```
    </Accordion>

    <Accordion title="Store Metrics">
      Document counts per collection

      ```json theme={null} theme={null} theme={null} theme={null} theme={null} theme={null}
      {
        "key": "collection_num_docs[orders]",
        "namespace": "store",
        "timestamp": 1762469342,
        "value": 5030
      }
      ```

      ```json theme={null} theme={null} theme={null} theme={null} theme={null} theme={null}
      {
        "key": "collection_num_docs[menus]",
        "namespace": "store",
        "timestamp": 1762469342,
        "value": 780
      }
      ```

      ```json theme={null} theme={null} theme={null} theme={null} theme={null} theme={null}
      {
        "key": "collection_num_docs[__collections]",
        "namespace": "store",
        "timestamp": 1762469342,
        "value": 29
      }
      ```

      ```json theme={null} theme={null} theme={null} theme={null} theme={null} theme={null}
      {
        "key": "collection_num_docs[__presence]",
        "namespace": "store",
        "timestamp": 1762469342,
        "value": 5
      }
      ```
    </Accordion>

    <Accordion title="Active Subscriptions">
      Local observer subscriptions currently registered

      ```json theme={null} theme={null} theme={null} theme={null} theme={null} theme={null}
      {
        "key": "local_subscriptions[SELECT * FROM orders]",
        "namespace": "replication",
        "timestamp": 1762469332,
        "value": null
      }
      ```

      ```json theme={null} theme={null} theme={null} theme={null} theme={null} theme={null}
      {
        "key": "local_subscriptions[SELECT * FROM menus]",
        "namespace": "replication",
        "timestamp": 1762469332,
        "value": null
      }
      ```

      ```json theme={null} theme={null} theme={null} theme={null} theme={null} theme={null}
      {
        "key": "local_subscriptions[SELECT * FROM COLLECTION __presence WHERE v == 3 && t > 1762387200000]",
        "namespace": "replication",
        "timestamp": 1762469332,
        "value": null
      }
      ```
    </Accordion>

    <Accordion title="Connectivity">
      Active peer connections by transport type (Bluetooth, LAN, P2P WiFi, WebSocket, Access Point), cloud connection status, and device name

      ```json theme={null} theme={null} theme={null} theme={null} theme={null} theme={null}
      {
        "key": "connections_bluetooth",
        "namespace": "presence",
        "timestamp": 1760652643,
        "value": 0
      }
      ```

      ```json theme={null} theme={null} theme={null} theme={null} theme={null} theme={null}
      {
        "key": "connections_p2pwifi",
        "namespace": "presence",
        "timestamp": 1760966174,
        "value": 2
      }
      ```

      ```json theme={null} theme={null} theme={null} theme={null} theme={null} theme={null}
      {
        "key": "connections_websocket",
        "namespace": "presence",
        "timestamp": 1760652643,
        "value": 0
      }
      ```

      ```json theme={null} theme={null} theme={null} theme={null} theme={null} theme={null}
      {
        "key": "connections_accesspoint",
        "namespace": "presence",
        "timestamp": 1760968133,
        "value": 2
      }
      ```

      ```json theme={null} theme={null} theme={null} theme={null} theme={null} theme={null}
      {
        "key": "is_connected_to_ditto_cloud",
        "namespace": "presence",
        "timestamp": 1762469340,
        "value": true
      }
      ```

      ```json theme={null} theme={null} theme={null} theme={null} theme={null} theme={null}
      {
        "key": "device_name",
        "namespace": "presence",
        "timestamp": 1762469339,
        "value": "DTO-A116"
      }
      ```
    </Accordion>

    <Accordion title="Logging Configuration">
      Whether logging is enabled and minimum log level

      ```json theme={null} theme={null} theme={null} theme={null} theme={null} theme={null}
      {
        "key": "enabled",
        "namespace": "logs",
        "timestamp": 1762469332,
        "value": false
      }
      ```

      ```json theme={null} theme={null} theme={null} theme={null} theme={null} theme={null}
      {
        "key": "minimum_level",
        "namespace": "logs",
        "timestamp": 1762469332,
        "value": "WARN"
      }
      ```
    </Accordion>

    <Accordion title="Eviction on Deleted Documents (Reaper)">
      Last reaper execution time and number of tombstones reaped

      ```json theme={null} theme={null} theme={null} theme={null} theme={null} theme={null}
      {
        "key": "last_reap_time",
        "namespace": "reaper",
        "timestamp": 1760909557,
        "value": "2025-10-19T21:32:37.211Z"
      }
      ```

      ```json theme={null} theme={null} theme={null} theme={null} theme={null} theme={null}
      {
        "key": "num_tombstones_reaped",
        "namespace": "reaper",
        "timestamp": 1760909557,
        "value": 0
      }
      ```
    </Accordion>
  </AccordionGroup>

  ### Usage

  Query the collection using standard DQL:

  ```sql theme={null} theme={null} theme={null} theme={null} theme={null} theme={null}
  SELECT * FROM system:system_info
  WHERE key LIKE 'collection_num_docs%'
  ```

  This collection is useful for debugging, monitoring storage usage, and understanding your Ditto instance configuration at runtime.

  ## Additional Improvements

  ### Connection & Network Reliability

  * **Smarter logging**: Connection failures now use adaptive log levels, starting at warning and escalating to error only after repeated failures, reducing log noise during temporary network issues
  * **Parallel connections**: TCP client now attempts to connect to all discovered addresses in parallel for faster, more reliable connections
  * **mDNS optimization**: mDNS now only advertises connectable addresses based on TCP server binding configuration
  * **Callback handling**: Fixed issue where long-running connection callbacks could cause timeout failures

  ### Attachment Access Improvements

  * **Fixed attachment retrieval**: Resolved an issue where attachment requests would sometimes fail to resolve even when the attachment was available locally, making attachment access more reliable

  ### Bug Fixes & Stability

  * Fixed memory leak in disk usage monitoring
  * Fixed bug causing small peers to re-upload logs on every startup
  * Fixed post-eviction cleanup to properly retain metadata for non-evicted documents in disconnected sync sessions
  * Improved logging for document deserialization errors

  ## 4.13 Full Change Log

  <AccordionGroup>
    <Accordion title="Common Changes">
      <Icon icon="screwdriver-wrench" iconType="solid" horizontal /> **Fixed**: disk usage monitoring no longer leaks memory. (#18531)

      <Icon icon="rotate-reverse" iconType="solid" horizontal /> **Changed**: Connection failures now use smart log levels, starting at warning and escalating to error only after repeated failures. (#18779)

      <Icon icon="rotate-reverse" iconType="solid" horizontal /> **Changed**: mDNS now only advertises connectable addresses based on TCP server binding address. TCP Client now attempts to connect to all addresses in parallel (#18930)

      <Icon icon="rotate-reverse" iconType="solid" horizontal /> **Changed**: the default value of `ENABLE_ATTACHMENT_PERMISSION_CHECKS` store configuration parameter to `false` (#18931)

      <Icon icon="plus" iconType="solid" horizontal /> **Added**: `system:system_info` virtual collection for DQL access to system info (#CORE-751)

      <Icon icon="screwdriver-wrench" iconType="solid" horizontal /> **Fixed**: A bug that caused small peers to re-upload remotely requested logs on every startup (#CORE-810)

      **Performance**: Document sync avoids sending large, redundant updates after reconnecting a long-dormant session between two peers that are otherwise well-synced with the mesh. (#DS-433)

      <Icon icon="rotate-reverse" iconType="solid" horizontal /> **Changed**: Improved avoidance of large redundant doc sync updates after session reconnect, based on the number of diffs sent in the initial post-reconnect update. (#DS-475)

      <Icon icon="screwdriver-wrench" iconType="solid" horizontal /> **Fixed**: Post eviction cleanup of disconnected document sync sessions now retains metadata for non-evicted documents. (#DS-487)

      <Icon icon="plus" iconType="solid" horizontal /> **Added**: Improved logging for document deserialization errors (#DS-568)

      <Icon icon="plus" iconType="solid" horizontal /> **Added**: UNION & INTERSECT scans. (#QE-398)

      <Icon icon="plus" iconType="solid" horizontal /> **Added**: Index support for array-based `IN` and `NOT IN` filter expressions in DQL queries. (#QE-417)

      <Icon icon="screwdriver-wrench" iconType="solid" horizontal /> **Fixed**: A long-running on connecting callback no longer causes `ReceiveTimeout` failures in connectivity. (#TRAN-729)
    </Accordion>
  </AccordionGroup>
</Update>

<Update label="4.12.5" description="Release Date: Mar 31, 2026">
  ## 4.12.5 Common Changes

  **Performance**: Disk usage monitor now runs on a dedicated thread, reducing blocking operations that might impact performance. (#20191)

  <Icon icon="screwdriver-wrench" iconType="solid" horizontal /> **Fixed**: A deadlock could occur where a device would fail to establish new P2P connections until restarted. (#20810)

  <Icon icon="screwdriver-wrench" iconType="solid" horizontal /> **Fixed**: A race condition where `fetchAttachment` could permanently fail to find locally-created attachments due to stale in-memory cache entries. (#21146)

  <Icon icon="plus" iconType="solid" horizontal /> **Added**: The thread ID is now included in small peer console logs. (#CORE-1201)

  <Icon icon="rotate-reverse" iconType="solid" horizontal /> **Changed**: Query engine operator execution logs now identify which operator is being executed. (#CORE-1266)

  <Icon icon="plus" iconType="solid" horizontal /> **Added**: The number of tokio worker and/or blocking threads can now be configured by setting the `DITTO_TOKIO_WORKER_THREADS` and `DITTO_TOKIO_BLOCKING_THREADS` environment variables. (#CORE-1273)

  **Performance**: Store observer no longer re-queries unrelated collections when writes occur. (#CORE-1389)

  **Performance**: Observers using a single ID equality builder query now shortcut all query execution and get the document directly in constant time. (#CORE-1433)

  <Icon icon="rotate-reverse" iconType="solid" horizontal /> **Changed**: Write transaction diagnostic logs now include the blocking transaction's current operation, elapsed time, and queue depth. (#CORE-1449)

  <Icon icon="screwdriver-wrench" iconType="solid" horizontal /> **Fixed**: High latency when write transactions trigger evictions. (#CORE-1453)

  **Performance**: Improved write performance during rapid eviction bursts by coalescing redundant garbage collection jobs that competed for CPU and disk I/O. (#CORE-1453)

  <Icon icon="rotate-reverse" iconType="solid" horizontal /> **Changed**: More information is logged at debug level around peer GC and eviction progress including what remote peers are being deleted. (#CORE-1455)

  <Icon icon="rotate-reverse" iconType="solid" horizontal /> **Changed**: More information is logged when a Ditto peer receives data that it cannot deserialize due to a hash mismatch. (#CORE-897)

  <Icon icon="rotate-reverse" iconType="solid" horizontal /> **Changed**: We now make an additional attempt to recover from some kinds of document deserialization errors, which may reduce errors or crashes due to deserialization. (#CORE-916)

  <Icon icon="plus" iconType="solid" horizontal /> **Added**: Automatic generation of USE IDS clause from \_id equality predicates when possible. (#QE-313)

  <Icon icon="plus" iconType="solid" horizontal /> **Added**: Periodic dumping of the Query Engine system:request\_history cache to the Ditto log for debugging purposes. (#QE-583)

  <Icon icon="screwdriver-wrench" iconType="solid" horizontal /> **Fixed**: A long-running on connecting callback no longer causes `ReceiveTimeout` failures in connectivity. (#TRAN-729)
</Update>

<Update label="4.12.4" description="Release Date: Oct 29, 2025">
  ## 4.12.4 Common Changes

  <Icon icon="screwdriver-wrench" iconType="solid" horizontal /> **Fixed**: disk usage monitoring no longer leaks memory. (#18531)

  <Icon icon="rotate-reverse" iconType="solid" horizontal /> **Changed**: mDNS now only advertises connectable addresses based on TCP server binding address. TCP Client now attempts to connect to all addresses in parallel. (#18930)

  <Icon icon="screwdriver-wrench" iconType="solid" horizontal /> **Fixed**: a bug that caused small peers to re-upload remotely requested logs on every startup. (#CORE-810)
</Update>

<Update label="4.12.3" description="Release Date: Oct 09, 2025">
  ## 4.12.3 Common Changes

  <Icon icon="rotate-reverse" iconType="solid" horizontal /> **Changed**: Enabled opentelemetry tracing in core. (#18464)

  <Icon icon="screwdriver-wrench" iconType="solid" horizontal /> **Fixed**: An issue where peers could fail to connect other local peers via mDNS on macOS. (#18488)

  <Icon icon="screwdriver-wrench" iconType="solid" horizontal /> **Fixed**: a bug that meant document id indexes were not created. (#18512)

  <Icon icon="screwdriver-wrench" iconType="solid" horizontal /> **Fixed**: Document sync session metadata became unlinked after session reset. (#DS-509)

  <Icon icon="plus" iconType="solid" horizontal /> **Added**: Improved logging for document deserialization errors. (#DS-568)

  <Icon icon="plus" iconType="solid" horizontal /> **Added**: query vitals. (#QE-296)

  <Icon icon="screwdriver-wrench" iconType="solid" horizontal /> **Fixed**: Performance of the DQL parser for large statements. (#QE-321)

  <Icon icon="screwdriver-wrench" iconType="solid" horizontal /> **Fixed**: Issue with planner picking an index when an `OR` is present in a statement's predicate leading to partial results. (#QE-373)

  <Icon icon="screwdriver-wrench" iconType="solid" horizontal /> **Fixed**: Planner not selecting an index for `_id` field filters. (#QE-374)

  <Icon icon="screwdriver-wrench" iconType="solid" horizontal /> **Fixed**: Android devices that fail to acquire an IP address will now continue to sync over LAN. (#TRAN-725)

  <Icon icon="screwdriver-wrench" iconType="solid" horizontal /> **Fixed**: A long-running connection request handler no longer causes `ReceiveTimeout` failures in connectivity. (#TRAN-729)
</Update>

<Update label="4.12.2" description="Release Date: Sep 30, 2025">
  ## 4.12.2 Common Changes

  <Icon icon="plus" iconType="solid" horizontal /> **Added**: Explicit log flushing before aborting due to panic (#CORE-723)

  <Icon icon="rotate-reverse" iconType="solid" horizontal /> **Changed**: on-disk log file limits now apply to the compressed size, significantly increasing log retention (#CORE-729)

  <Icon icon="screwdriver-wrench" iconType="solid" horizontal /> **Fixed**: A rare scenario where an attachment fetch could be delayed by up to 60 seconds. (#DS-461)

  <Icon icon="plus" iconType="solid" horizontal /> **Added**: query vitals (#QE-296)

  <Icon icon="screwdriver-wrench" iconType="solid" horizontal /> **Fixed**: use deterministic summaries for documents created by observers (#QE-310)
</Update>

<Update label="4.12.1" description="Release Date: Sep 03, 2025">
  ## 4.12.1 Rust Specific Changes

  <Icon icon="screwdriver-wrench" iconType="solid" horizontal /> **Fixed**: Removed implicit cloud-sync for revamped Ditto init (#17977)

  ## 4.12.1 Common Changes

  <Icon icon="screwdriver-wrench" iconType="solid" horizontal /> **Fixed**: A bug where x509 refresh could speed up uncontrollably. (#17947)

  <Icon icon="screwdriver-wrench" iconType="solid" horizontal /> **Fixed**: A bug where a peer could get stuck with incorrect connection information. (#17967)

  <Icon icon="plus" iconType="solid" horizontal /> **Added**: `ENABLE_ATTACHMENT_PERMISSION_CHECKS` ALTER SYSTEM parameter to be set to `false` to avoid certain rare cases of attachment fetcher hanging (#18016)

  <Icon icon="screwdriver-wrench" iconType="solid" horizontal /> **Fixed**: Network connections close gracefully when Ditto is stopped. (#18053)

  <Icon icon="screwdriver-wrench" iconType="solid" horizontal /> **Fixed**: The `system:data_sync_info` collection may briefly report sync immediately after connecting (#18137)

  **Other**: improve error reporting for document (de)serialization (#18165)

  <Icon icon="screwdriver-wrench" iconType="solid" horizontal /> **Fixed**: Live queries being unable to use indices. (#DS-447)

  <Icon icon="screwdriver-wrench" iconType="solid" horizontal /> **Fixed**: Use of DISTINCT with ORDER BY & OFFSET/LIMIT. (#QE-281)
</Update>

<Update label="4.12.0" description="Release Date: Aug 14, 2025">
  ## 4.12 - DQL Enhancements & Platform Expansion

  Version 4.12 brings significant enhancements to DQL (Ditto Query Language) with production-ready projections and aggregates, expanded platform support with Flutter for Linux and macOS, and marks the deprecation of legacy query builder APIs in preparation for DQL as the primary interface.

  ## DQL Projections & Aggregates

  DQL projections and aggregates are now out of preview and fully production-ready. These powerful features enable sophisticated data analysis and optimized query performance directly within DQL.

  ### Projections

  Select specific fields and create calculated columns to reduce data transfer and processing:

  ```sql DQL theme={null} theme={null} theme={null} theme={null} theme={null} theme={null}
  -- Select specific fields
  SELECT make, model, year FROM cars

  -- Create calculated fields with aliases
  SELECT make, model, price * 0.9 AS discounted_price FROM cars

  -- Remove duplicates
  SELECT DISTINCT color FROM cars
  ```

  ### Aggregate Functions

  Perform calculations across multiple documents with SQL-standard aggregate functions:

  ```sql DQL theme={null} theme={null} theme={null} theme={null} theme={null} theme={null}
  -- Count documents
  SELECT COUNT(*) AS total_cars FROM cars

  -- Calculate statistics
  SELECT 
    AVG(price) AS avg_price,
    MIN(price) AS lowest_price,
    MAX(price) AS highest_price,
    SUM(price) AS total_value
  FROM cars

  -- Group and aggregate
  SELECT make, COUNT(*) AS models, AVG(price) AS avg_price
  FROM cars
  GROUP BY make
  HAVING COUNT(*) > 3
  ```

  <Tip>For complete documentation, see [DQL SELECT operations](/dql/select)</Tip>

  ## DQL Index Management

  Create and manage indexes directly through DQL for improved query performance:

  ```sql DQL theme={null} theme={null} theme={null} theme={null} theme={null} theme={null}
  -- Create an index
  CREATE INDEX idx_cars_make ON cars (make)

  -- Drop an index
  DROP INDEX idx_cars_make ON cars

  -- View all indexes
  SELECT * FROM system::dql_indexes
  ```

  <Tip>For complete documentation, see [DQL Indexing](/dql/indexing)</Tip>

  ## Flutter Platform Expansion

  ### Linux Support

  Flutter developers can now build and deploy Ditto-powered applications on Linux desktops:

  * Native Linux binary (`libdittoffi.so`) included
  * Full support for development, testing, and production deployments
  * Configurable binary path via `$LIBDITTOFFI_PATH` environment variable
  * Compatible with Flutter's standard Linux development workflow

  <Tip>See [Flutter Install Guide](/sdk/latest/install-guides/flutter) for Linux setup instructions</Tip>

  ## Legacy Query Builder Deprecation

  The entire legacy query builder API is deprecated across all SDKs. Developers should migrate to DQL for all data operations:

  **Migration Benefits:**

  * SQL-like syntax familiar to developers
  * Unified interface for all data operations
  * Better performance and optimization
  * More powerful query capabilities

  <Warning>
    Legacy query builder APIs will be removed in SDK v5. Start migrating to DQL now using the [migration guide](https://docs.ditto.live/dql/legacy-to-dql-adoption).
  </Warning>

  ## Additional Enhancements

  ### System Improvements

  * **Enhanced disk observer**: Now enabled at startup with configurable batch settings
  * **Improved error handling**: Better error propagation and syntax error identification in DQL
  * **Memory optimizations**: Reduced memory usage for aggregate operations and projections

  ### DQL Function Additions

  * Duration scalar functions for date/time calculations
  * Dynamic field references in queries
  * Support for arrays as operation values
  * Extended multiplication operations for better numeric handling

  ### Security & Diagnostics

  * Support for `SSLKEYLOGFILE` for debugging TLS connections
  * New `system::data_sync_info` virtual collection for sync diagnostics
  * Transport diagnostics APIs across multiple SDKs

  ## Upgrading to 4.12

  To take advantage of these new features:

  1. Update your SDK to version 4.12.0 or later
  2. Begin migrating legacy query builder code to DQL
  3. Explore projections and aggregates for query optimization
  4. Consider Flutter Linux support for desktop deployments

  <Note>
    Version 4.12 maintains full backward compatibility while encouraging migration to modern DQL APIs. Legacy APIs continue to function but should be replaced in preparation for SDK v5.
  </Note>

  ## 4.12.0 Common Changelog

  ### Added

  * The `transports_discovered_peers` system parameter to dynamically update peers discovered out-of-band (#17009)
  * The new `system::indexes` virtual collection for viewing DQL indexes on small peers (#17011)
  * Support for `SSLKEYLOGFILE` for inspecting network traffic in tools like Wireshark (#17029)
  * `UPDATE_LOCAL_DIFF` id conflict strategy for INSERT statements (#17310)
  * A system:data\_sync\_info virtual collection that exposes per-remote data sync status via DQL (#17360)
  * `transports_tcp_so_nodelay` system parameter to control TCP\_NODELAY for TCP and TCP-based websockets connections (#17673)
  * Additional metadata to keep track of the timestamp of the last update file received (#DS-290)
  * Observers for DQL queries can now access system virtual collections (#DS-294)
  * Query executor runner to observers - they now support all of the new DQL features like projections, aggregates, use ids... (#QE-143)
  * SYSTEM:COLLECTIONS & SYSTEM:ALL\_COLLECTIONS virtual collections to list accessible collections (#QE-146)
  * Support for ARRAYs as the value options list in IN DQL expressions (#QE-167)
  * DQL scalar functions for durations (#QE-170)
  * DQL support for CREATE INDEX (#QE-182)
  * DQL support for DROP INDEX (#QE-183)
  * Support for dynamic field references in DQL statements (#QE-2)
  * Query request history cache qualifiers for system datasource deletes and general mutations (#QE-207)
  * Basic RBO for index scan selection (#QE-210)
  * Query parser handles context dependent keyword (#QE-241)
  * Virtual collections for active and historical DQL engine requests (#QE-82)

  ### Changed

  * device\_disk\_observer\_is\_enabled system parameter can now be changed at runtime (#CORE-612)
  * After eviction, document sync now retains high-level session metadata for non-expired sessions, for sync status tracking purposes (#DS-348)
  * Projection, distinct and aggregate features out of preview mode! (#QE-100)
  * Wildcard expansion to top-level with left-to-right, last-wins projection aliasing (#QE-156)
  * Improved ScalarExpr representation in EXPLAIN output (#QE-193)
  * Improved syntax error identification in UPDATE statements (#QE-199)
  * ALTER SYSTEM DQL statements now accept static expressions (#QE-204)
  * USE IDS clause to accept expressions that can be statically evaluated (#QE-217)
  * Permit use of unary plus in DQL expressions (#QE-220)
  * Extended DQL multiplication to better handle multiplying two large negative integers (#QE-224)
  * Query directives processing to accept USE INDEX as the equivalent of USE DIRECTIVES `{"#index":...}` (#QE-255)
  * CREATE & DROP INDEX statements accept IF \[NOT] EXISTS to permit repeated execution without error (#QE-259)
  * Websocket connectivity errors are now logged with additional detail (#TRAN-511)
  * Ditto no longer includes a peer's device name and OS during P2P advertisement (BLE, mDNS, Wi-Fi Aware, AWDL) (#TRAN-652)

  ### Fixed

  * A rare race condition which caused connection handshakes to erroneously fail (#17251)
  * Merge tombstone summaries when applying remote tombstone (#17654)
  * Set default TCP\_NODELAY socket option to true to improve latency, notably on Linux (#17673)
  * DQL collation order is based on length of arrays / objects, not padding values with extra MISSING (#QE-171)
  * DQL scalar function clock() and "local" timezone in WASM environments (#QE-181)
  * Error propagation from collection scans (#QE-191)
  * Collation in DQL aggregates (#QE-216)
  * Panic when using COUNT(\*) in a dynamic object (#QE-219)
  * Panic when subtracting a large positive integer value from a large negative integer value (#QE-223)
  * Aggregate output on empty result sets (#QE-242)

  ### Performance

  * Revised fetching documents by ID in Query to operate in batches (#QE-248)

  ### Other

  * Added a warning to the log when a subscription query uses a LIMIT or ORDER BY (#QE-169)

  ## 4.12.0 Rust Specific Changes

  <Icon icon="plus" iconType="solid" horizontal /> **Added**: The `transports_discovered_peers` system parameter to dynamically update peers discovered out-of-band. (#17009)

  <Icon icon="plus" iconType="solid" horizontal /> **Added**: The new `system::indexes` virtual collection for viewing DQL indexes on small peers. (#17011)

  <Icon icon="plus" iconType="solid" horizontal /> **Added**: we now support `SSLKEYLOGFILE` for inspecting network traffic in tools like Wireshark. (#17029)

  <Icon icon="screwdriver-wrench" iconType="solid" horizontal /> **Fixed**: A rare race condition which caused connection handshakes to erroneously fail. (#17251)

  <Icon icon="plus" iconType="solid" horizontal /> **Added**: `UPDATE_LOCAL_DIFF` id conflict strategy for INSERT statements (#17310)

  <Icon icon="plus" iconType="solid" horizontal /> **Added**: A system:data\_sync\_info virtual collection that exposes per-remote data sync status via DQL (#17360)

  <Icon icon="screwdriver-wrench" iconType="solid" horizontal /> **Fixed**: merge tombstone summaries when applying remote tombstone (#17654)

  **Performance**: set default TCP\_NODELAY socket option to true to improve latency, notably on Linux  (#17673)

  <Icon icon="plus" iconType="solid" horizontal /> **Added**: `transports_tcp_so_nodelay` system parameter to control TCP\_NODELAY for TCP and TCP-based websockets connections

  <Icon icon="rotate-reverse" iconType="solid" horizontal /> **Changed**: device\_disk\_observer\_is\_enabled system parameter can now be changed at runtime (#CORE-612)

  <Icon icon="plus" iconType="solid" horizontal /> **Added**: Additional metadata to keep track of the timestamp of the last update file received. (#DS-290)

  <Icon icon="plus" iconType="solid" horizontal /> **Added**: Observers for DQL queries can now access system virtual collections. (#DS-294)

  <Icon icon="rotate-reverse" iconType="solid" horizontal /> **Changed**: After eviction, document sync now retains high-level session metadata for non-expired sessions, for sync status tracking purposes. (#DS-348)

  <Icon icon="rotate-reverse" iconType="solid" horizontal /> **Changed**: projection, distinct and aggregate features out of preview mode! (#QE-100)

  <Icon icon="plus" iconType="solid" horizontal /> **Added**: query executor runner to observers - they now support all of the new DQL features like projections, aggregates, use ids... (#QE-143)

  <Icon icon="plus" iconType="solid" horizontal /> **Added**: SYSTEM:COLLECTIONS & SYSTEM:ALL\_COLLECTIONS virtual collections to list accessible collections. (#QE-146)

  <Icon icon="rotate-reverse" iconType="solid" horizontal /> **Changed**: Wildcard expansion to top-level with left-to-right, last-wins projection aliasing. (#QE-156)

  <Icon icon="plus" iconType="solid" horizontal /> **Added**: Support for ARRAYs as the value options list in IN DQL expressions. (#QE-167)

  **Other**: Added a warning to the log when a subscription query uses a LIMIT or ORDER BY. (#QE-169)

  <Icon icon="plus" iconType="solid" horizontal /> **Added**: DQL scalar functions for durations. (#QE-170)

  <Icon icon="screwdriver-wrench" iconType="solid" horizontal /> **Fixed**: DQL collation order is based on length of arrays / objects, not padding values with extra MISSING (#QE-171)

  <Icon icon="screwdriver-wrench" iconType="solid" horizontal /> **Fixed**: DQL scalar function clock() and "local" timezone in WASM environments. (#QE-181)

  <Icon icon="plus" iconType="solid" horizontal /> **Added**: DQL support for CREATE INDEX (#QE-182)

  <Icon icon="plus" iconType="solid" horizontal /> **Added**: DQL support for DROP INDEX (#QE-183)

  <Icon icon="screwdriver-wrench" iconType="solid" horizontal /> **Fixed**: Error propagation from collection scans (#QE-191)

  <Icon icon="rotate-reverse" iconType="solid" horizontal /> **Changed**: Improved ScalarExpr representation in EXPLAIN output. (#QE-193)

  <Icon icon="rotate-reverse" iconType="solid" horizontal /> **Changed**: Improved syntax error identification in UPDATE statements. (#QE-199)

  <Icon icon="plus" iconType="solid" horizontal /> **Added**: Support for dynamic field references in DQL statements. (#QE-2)

  <Icon icon="rotate-reverse" iconType="solid" horizontal /> **Changed**: ALTER SYSTEM DQL statements now accept static expressions. (#QE-204)

  <Icon icon="plus" iconType="solid" horizontal /> **Added**: Query request history cache qualifiers for system datasource deletes and general mutations. (#QE-207)

  <Icon icon="plus" iconType="solid" horizontal /> **Added**: Basic RBO for index scan selection. (#QE-210)

  <Icon icon="screwdriver-wrench" iconType="solid" horizontal /> **Fixed**: Collation in DQL aggregates. (#QE-216)

  <Icon icon="rotate-reverse" iconType="solid" horizontal /> **Changed**: USE IDS clause to accept expressions that can be statically evaluated. (#QE-217)

  <Icon icon="screwdriver-wrench" iconType="solid" horizontal /> **Fixed**: Panic when using COUNT(\*) in a dynamic object. (#QE-219)

  <Icon icon="rotate-reverse" iconType="solid" horizontal /> **Changed**: Permit use of unary plus in DQL expressions. (#QE-220)

  <Icon icon="screwdriver-wrench" iconType="solid" horizontal /> **Fixed**: Panic when subtracting a large positive integer value from a large negative integer value. (#QE-223)

  <Icon icon="rotate-reverse" iconType="solid" horizontal /> **Changed**: Extended DQL multiplication to better handle multiplying two large negative integers. (#QE-224)

  <Icon icon="plus" iconType="solid" horizontal /> **Added**: query parser handles context dependent keyword (#QE-241)

  <Icon icon="screwdriver-wrench" iconType="solid" horizontal /> **Fixed**: Aggregate output on empty result sets. (#QE-242)

  **Performance**: Revised fetching documents by ID in Query to operate in batches. (#QE-248)

  <Icon icon="rotate-reverse" iconType="solid" horizontal /> **Changed**: Query directives processing to accept USE INDEX as the equivalent of USE DIRECTIVES '\{"#index":...}' (#QE-255)

  <Icon icon="rotate-reverse" iconType="solid" horizontal /> **Changed**: CREATE & DROP INDEX statements accept IF \[NOT] EXISTS to permit repeated execution without error. (#QE-259)

  <Icon icon="plus" iconType="solid" horizontal /> **Added**: Virtual collections for active and historical DQL engine requests. (#QE-82)

  <Icon icon="rotate-reverse" iconType="solid" horizontal /> **Changed**: Websocket connectivity errors are now longed with additional detail. (#TRAN-511)

  <Icon icon="rotate-reverse" iconType="solid" horizontal /> **Changed**: Ditto no longer includes a peer's device name and OS during P2P advertisement (BLE, mDNS, Wi-Fi Aware, AWDL) (#TRAN-652)
</Update>

<Update label="4.11.6" description="Release Date: Oct 14, 2025">
  ## 4.11.6 Common Changes

  <Icon icon="screwdriver-wrench" iconType="solid" horizontal /> **Fixed**: disk usage monitoring no longer leaks memory. (#18531)

  <Icon icon="screwdriver-wrench" iconType="solid" horizontal /> **Fixed**: Document sync session metadata became unlinked after session reset. (#DS-509)

  <Icon icon="rotate-reverse" iconType="solid" horizontal /> **Changed**: Improved logging and error handling for handle\_get\_txid\_query.
</Update>

<Update label="4.11.5" description="Release Date: Sep 25, 2025">
  ## 4.11.5 Common Changes

  **Other**: improve error reporting for document (de)serialization (#18165)

  <Icon icon="plus" iconType="solid" horizontal /> **Added**: Explicit log flushing before aborting due to panic (#CORE-723)

  <Icon icon="rotate-reverse" iconType="solid" horizontal /> **Changed**: on-disk log file limits now apply to the compressed size, significantly increasing log retention (#CORE-729)

  <Icon icon="screwdriver-wrench" iconType="solid" horizontal /> **Fixed**: A rare scenario where an attachment fetch could be delayed by up to 60 seconds. (#DS-461)
</Update>

<Update label="4.11.4" description="Release Date: Aug 28, 2025">
  ## 4.11.4 Common Changes

  <Icon icon="screwdriver-wrench" iconType="solid" horizontal /> **Fixed**: A bug where x509 refresh could speed up uncontrollably. (#17947)

  <Icon icon="screwdriver-wrench" iconType="solid" horizontal /> **Fixed**: A bug where a peer could get stuck with incorrect connection information. (#17967)
</Update>

<Update label="4.11.3" description="Release Date: Aug 15, 2025">
  ## 4.11.3 Common Changes

  <Icon icon="screwdriver-wrench" iconType="solid" horizontal /> **Fixed**: An issue with BLE on some Android 9 and earlier devices that prevented connection establishment. (#17760)
</Update>

<Update label="4.11.2" description="Release Date: Aug 1, 2025">
  ## 4.11.2 Common Changes

  <Icon icon="screwdriver-wrench" iconType="solid" horizontal /> **Fixed**: A rare race condition which caused connection handshakes to erroneously fail. (#17251)

  <Icon icon="rotate-reverse" iconType="solid" horizontal /> **Changed**: device\_disk\_observer\_is\_enabled system parameter can now be changed at runtime (#CORE-612)
</Update>

<Update label="4.11.1" description="Release Date: Jul 16, 2025">
  ## 4.11.1 Common Changes

  *No Specific Changes*
</Update>

<Update label="4.11.0 " description="Release Date: June 10, 2025">
  ## 4.11 - DQL & Legacy Compatibility

  With 4.11 we are excited to introduce legacy compatibility for DQL, which allows
  developers to use the new DQL APIs while maintaining compatibility with existing
  code and data. This capability, called [STRICT MODE](/dql/strict-mode), is designed to ease the transition
  to the new APIs and ensure that existing applications continue to function as
  expected.

  ## DQL Strict Mode

  DQL Strict Mode provides control over how DQL statements are evaluated and how
  data types are inferred. When disabled, it offers more flexibility in working
  with documents without requiring explicit collection definitions.

  <Tip>For more information see [`DQL Strict Mode`](/dql/strict-mode)</Tip>

  With strict mode disabled (`DQL_STRICT_MODE=false`), Ditto is more flexible and will infer the CRDT type based on the document's shape:

  * Objects are treated as CRDT maps
  * Scalars and arrays are treated as Registers
  * Counters and attachments are inferred from operations
  * Collection definitions are no longer required

  **Setting DQL Strict Mode**

  ```sql DQL theme={null} theme={null} theme={null} theme={null} theme={null} theme={null}
  ALTER SYSTEM SET DQL_STRICT_MODE = false
  ```

  ## DQL Differ

  DQL 4.11 introduces a new `Differ` API for calculating diffs between query results.
  This API can be used with a store observer to understand how its results change
  over successive callbacks. The `Differ` API provides a way to track changes in
  the data and can be used to optimize data synchronization and conflict resolution.

  [Differ API documentation](/sdk/latest/crud/read#diffing-results).

  ## DQL Transactions

  DQL 4.11 introduces support for *transactions*. Transactions can be used to group multiple DQL statements together, ensuring
  that either all of the statements are executed successfully or none of them are.
  This is particularly useful in scenarios where multiple updates or inserts
  need to be made to the database, and you want to ensure that either all of them
  are applied or none of them are.

  [Transactions API documentation](/sdk/latest/crud/transactions).

  ## Advanced DQL Features

  DQL 4.11 introduces numerous advanced querying and manipulation features:

  | Feature             | Description                                  | Example                                                                |
  | ------------------- | -------------------------------------------- | ---------------------------------------------------------------------- |
  | `UNSET` clause      | Remove fields from documents                 | `UPDATE orders UNSET items.abc WHERE _id = 'my-id'`                    |
  | CAST function       | Explicitly convert between data types        | `SELECT * FROM products WHERE CAST(price AS INT) > 10`                 |
  | USE IDS clause      | Direct document retrieval by ID              | `SELECT * FROM products USE IDS '123', '456'`                          |
  | SIMILAR TO          | Pattern matching expressions                 | `SELECT * FROM products WHERE name SIMILAR TO '%phone%'`               |
  | Runtime expressions | Use expressions in object/array construction | `UPDATE products SET metadata = { 'updated_at': current_timestamp() }` |
  | Counters            | Support for legacy compatible counter type   | `UPDATE products APPLY in_stock PN_INCREMENT BY 1.0`                   |

  <Warning>
    In 4.11, functional operations are denoted with an arrow (`->`) are deprecated. [Read more](https://docs.ditto.live/dql/update#update-multiple-fields).
  </Warning>

  ## Tombstone Reaper

  The tombstone reaper is now enabled by default for all SDKs. This feature helps
  clean up deleted document markers (tombstones) to improve database performance
  and reduce storage requirements.

  The reaper:

  * Automatically removes tombstones after a configurable time-to-live (TTL)
  * Uses read transactions for efficiency
  * Includes random scheduling variations to prevent performance problems
  * Tracks the number of tombstones evicted for monitoring
  * Remembers previous reap times across restarts

  This improves overall system performance by reducing the long-term accumulation of
  tombstones when calling `DELETE` to remove documents.

  ## 4.11.0 Common Changelog

  ### Added

  * Introduced `DQL_STRICT_MODE` as a system parameter to opt-out of requiring collection definitions (#16573)
  * Added transports\_ble\_adapter\_mac system parameter to allow configuring bluetooth adapter MAC address (#16159)
  * Small peers now log the result of OnlinePlayground authentication, including if the supplied shared token was incorrect (#16301)
  * A cumulative running total of the number of tombstones ever evicted by the reaper to Small Peer Info (#16424)
  * Added system parameters to fine-tune Ditto behavior when it encounters a locked persistence directory (#CORE-479)
  * New DQL CAST function to explicitly cast between types (#QE-108)
  * Conditional functions for unknowns (#QE-111)
  * DQL DATE processing functions (#QE-112)
  * New DQL clause USE IDS for direct document retrieval by id (#QE-114)
  * Additional string functions (#QE-124)
  * SIMILAR TO filter expression (#QE-125)
  * PN\_COUNTER support (APPLY clause in UPDATE statement) (#QE-127)
  * UNSET clause to the UPDATE statement (#QE-128)
  * MERGE as an alias for UPDATE in the ON ID CONFLICT clause of an INSERT statement (#QE-132)
  * The ability to use runtime-evaluated expressions in object constructs in DQL statements (#QE-133)
  * The ability to use runtime-evaluated expressions in array constructs in DQL statements (#QE-134)
  * Static expressions in mutators (#QE-139)
  * Additional object manipulation DQL scalar functions (#QE-159)
  * EXPLAIN for query plan (#QE-105)
  * More detailed messages about network problems are logged when authentication fails (#SEC-124)

  ### Changed

  * Use the modern rustls-platform-verifier TLS crate on all platforms rather than rustls-native-certs (#15956)
  * The tombstone reaper scheduling to remember the previous reap times across shutdown and restart of the small peer (#16237)
  * The tombstone reaper scheduling code to add random variations, which helps prevent performance problems if/when all peers run the reaper simultaneously (#16286)
  * The tombstone reaper to be enabled by default for all SDKs (#16350)
  * INSERT to now accept either DOCUMENTS or VALUES as the keyword introducing the list of values to insert (#QE-140)
  * Date functions accept "local" as a timezone & use the executing peer's local timezone (#QE-168)
  * Unified dedicated TCP servers across different transports (Multicast, mDNS, and WiFi Aware) by utilizing a single static TCP server implementation (#TRANS-131)

  ### Fixed

  * Fixed issue where user\_collection\_sync\_scopes could not be updated after initial set (#16299)
  * Fixed: A rare crash on Android devices when shutting down Bluetooth. (#17069)
  * Fixed: Bluetooth connectivity on Apple devices works when background Bluetooth permissions are missing. (#17065)

  ### Removed

  * Old multihop networking stack and system parameter `network_use_nextgen_multihop_stack` (#16370)
  * TLS certificate compression, which led to incompatibilities (#SDKS-1046)

  ### Performance

  * The tombstone reaper uses read transactions for some of its work instead of holding open a long-running write transaction, thus reducing contention on the small peer database (#16338)
  * Improved speed and efficiency of the tombstone reaping process (#16535)

  ## 4.11.0 Rust Specific Changes

  <Icon icon="rotate-reverse" iconType="solid" horizontal /> **Changed**: New and improved DQL APIs (#16651)

  <Icon icon="plus" iconType="solid" horizontal /> **Added**: struct `Differ`, which calculates diffs between query results. This can be used with a store observer to understand how its results change over successive callbacks. (#SDKS-986)

  <Icon icon="plus" iconType="solid" horizontal /> **Added**: struct `Diff` to represent diffs produced by the `Differ`. (#SDKS-986)
</Update>

<Update label="4.10.5 " description="Release Date: Jun 24, 2025">
  ## 4.10.5 Rust Specific Changes

  <Icon icon="screwdriver-wrench" iconType="solid" horizontal /> **Fixed**: Windows devices failed to connect to Android on LAN (#17199)

  ## 4.10.5 Common Changes

  *No Specific Changes*
</Update>

<Update label="4.10.2 " description="Release Date: Apr 25, 2025">
  ## 4.10.2 Common Changes

  <Icon icon="bin-recycle" iconType="solid" horizontal /> **Removed**: zlib certificate compression for small peer TLS 1.3 session negotiation, which caused incompatibilities (#1005)
</Update>

<Update label="4.10.1 " description="Release Date: Apr 02, 2025">
  ## 4.10.1 Common Changes

  <Icon icon="rotate-reverse" iconType="solid" horizontal /> **Changed**: The tombstone reaper scheduling to remember the previous reap times across shutdown and restart of the small peer. (#16237)

  <Icon icon="rotate-reverse" iconType="solid" horizontal /> **Changed**: the tombstone reaper scheduling code to add random variations, which helps prevent performance problems if/when all peers run the reaper simultaneously. (#16286)

  <Icon icon="screwdriver-wrench" iconType="solid" horizontal /> **Fixed**: Unable to update user\_collection\_sync\_scopes after initial set bug (#16299)

  **Performance**: The tombstone reaper uses read transactions for some of its work instead of holding open a long-running write transaction, thus reducing contention on the small peer database. (#16338)

  <Icon icon="rotate-reverse" iconType="solid" horizontal /> **Changed**: The tombstone reaper to be enabled by default for all SDKs. (#16350)
</Update>

<Update label="4.10.0" description="Release Date: March 14, 2025">
  # 4.10.0 New Capabilities

  <Capabilities4_10 />

  ## 4.10.0 Rust Specific Changelog

  * `BatchIdOperation::exec` to allow getting a specific document within the scope of a write transaction block. (#SDKS-425)
  * Repeated reads of a document within an ID-specific transaction scope of the query builder API now reflect changes made in the same transaction. (SDKS-245)
  * (Experimental) Bus API correctly falls back to multihop connectivity if a direct connection is lost. (#15670)
  * Deprecated `arm-unknown-linux-gnueabihf` target from support due to missing internal coverage and usage. (#15795)

  <Changelog4_10 />
</Update>

<Update label="4.9.4 " description="Release Date: Feb 17, 2025">
  ## 4.9.4 Common Changes

  <Icon icon="plus" iconType="solid" horizontal /> **Added:** new system parameter which defines the number of threads used by the store observer runtime to dispatch the sdk callback invocations. For more information reach out to Ditto's Support (#15814)
</Update>

<Update label="4.9.3 " description="Release Date: Jan 23, 2025">
  ## 4.9.3 Common Changes

  <Icon icon="rotate-reverse" iconType="solid" horizontal /> **Changed**: Added more actionable information to common connection handshake issues. (#15298)

  <Icon icon="screwdriver-wrench" iconType="solid" horizontal /> **Fixed:**  Fixed: Some Android devices could fail to export logs to the portal due to a file permissions error (#15582)
</Update>

<Update label="4.9.2 " description="Release Date: Dec 19, 2024">
  *No Rust Specific Changes*
</Update>

<Update label="4.9.1 " description="Release Date: Dec 13, 2024">
  ## 4.9.1 Common Changes

  <Icon icon="screwdriver-wrench" iconType="solid" horizontal /> **Fixed:** iOS 18 crashes related to Bluetooth LE are now resolved. (#15351)

  <Icon icon="screwdriver-wrench" iconType="solid" horizontal /> **Fixed:** Disk usage stats are now reported in small peer info on android devices
</Update>

<Update label="4.9.0 " description="Release Date: Nov 21, 2024">
  ## 4.9.0 Rust Specific Changes

  The 4.9.0 Rust release has come with a collection of API changes designed to align the Rust SDK with the standards of our other SDK. These changes were done to align naming conventions as well as to reorganize the module to make it more consistent with other SDKs.

  These API changes include a number of deprecated APIs. For instances where APIs are deprecated you'll find replacement APIs provided.

  All changes are backwards compatible.

  ### General Changes

  <Icon icon="screwdriver-wrench" iconType="solid" horizontal /> **Fixed**: Resolved an issue where store\_observer.is\_cancelled() could return incorrect values (#14419).

  <Icon icon="plus" iconType="solid" horizontal /> **Added**: ditto.update\_transport\_config() API (#5928)

  <Icon icon="plus" iconType="solid" horizontal /> **Added**: V3ConnectionType to provide internal access to a presence peer's connection type (#12945).

  <Icon icon="plus" iconType="solid" horizontal /> **Added**: #\[must\_use] attribute on Subscription, PresenceObserver, and LiveQuery to encourage correct usage (#13256).

  ### API Renaming

  <Icon icon="triangle-exclamation" iconType="solid" horizontal /> **Deprecated**: ditto.authenticator() & DittoAuthenticator::new(#13606, 13851)

  * Useditto.auth()

  <Icon icon="triangle-exclamation" iconType="solid" horizontal /> **Deprecated**: ditto.current\_transport\_config() (#13606).

  * Use ditto.transport\_config()

  <Icon icon="triangle-exclamation" iconType="solid" horizontal /> **Deprecated**: ditto.application\_id() (#13606).

  * Use ditto.app\_id()

  ### Module Reorganization

  ***Added a dedicated*** presence ***module for the Presence API***

  <Icon icon="triangle-exclamation" iconType="solid" horizontal /> **Deprecated**: dittolive\_ditto::transport::\{Peer, Presence, PresenceGraph, PresenceObserver, PresenceOs, Connection, ConnectionType} (#13645).

  * use dittolive\_ditto::presence::\{Peer, Presence, PresenceGraph, PresenceObserver, PresenceOs, Connection, ConnectionType}

  <Icon icon="plus" iconType="solid" horizontal /> **Added**: dittolive\_ditto::presence::\{ConnectionRequest, ConnectionRequestAuthorization} (previously only available via prelude) (#13645)

  ***Flattened store module, improved store docs***

  <Icon icon="rotate-reverse" iconType="solid" horizontal /> **Changed**: Moved store::dql module to crate-level

  <Icon icon="triangle-exclamation" iconType="solid" horizontal /> **Deprecated**: store::attachment, store::collection, and store::collections modules, with items moved to streamlined modules.

  * use store::attachment::\{FetcherVersion, DittoAttachmentFetcher, DittoAttachmentToken, DittoAttachmentFetchEvent, DittoAttachmentTokenLike}

  <Icon icon="triangle-exclamation" iconType="solid" horizontal /> **Deprecated**: store::collections::\{event, pending\_collections\_operation} modules

  * use store::collections::\{CollectionsEvent, PendingCollectionsOperation, CollectionsEventHandler}

  <Icon icon="triangle-exclamation" iconType="solid" horizontal /> **Deprecated**: store::collection::\{document, document\_id, pending\_cursor\_operation, pending\_id\_specific\_operation, type\_traits} modules

  * use store::collection::\{DocumentId, PendingCursorOperation, PendingIdSpecificOperation, DittoDocument, DittoMutDocument, MutableValue}

  <Icon icon="rotate-reverse" iconType="solid" horizontal /> **Changed**: Moved dql::\{StoreObserver, ChangeHandler, ChangeHandlerWithSignalNext, SignalNext} to the store module

  ***Additonal Module Changes***

  <Icon icon="rotate-reverse" iconType="solid" horizontal /> **Changed**: Moved SyncSubscription to sync module, updated docs (#13645)

  <Icon icon="bin-recycle" iconType="solid" horizontal /> **Removed**: ditto module from the public API (#13645).

  * Moved ditto module contents to crate-level (#13645)

  <Icon icon="triangle-exclamation" iconType="solid" horizontal /> **Deprecated**: the auth module, items moved to identity (#13645)

  <Icon icon="triangle-exclamation" iconType="solid" horizontal /> **Deprecated**: the observer module and Observer trait (#13645)

  <Icon icon="rotate-reverse" iconType="solid" horizontal /> **Changed**: Moved SyncSubscription to sync module (#13702)

  * Changed: Updated sync module docs (#13702)
  * Deprecated: dittolive\_ditto::store::dql::SyncSubscription
  * Added: dittolive\_ditto::sync::SyncSubscription

  <Icon icon="plus" iconType="solid" horizontal /> **Added**: DittoMutableCounter and DittoMutableRegister to prelude

  <Icon icon="plus" iconType="solid" horizontal /> **Added**: New store::query\_builder module as home for all QueryBuilder types (#14162)

  * Deprecated: crate-level types module, contents moved into query\_builder
  * Deprecated: store::\{batch,collection,collections,live\_query,update} modules, contents moved into query\_builder
  * Deprecated: crate-level subscription module, Subscription moved into query\_builder module

  ### Deprecated unused and unintentionally exposed items

  <Icon icon="triangle-exclamation" iconType="solid" horizontal /> **Deprecated**: removed ValidityListener from public API (#13857)

  <Icon icon="triangle-exclamation" iconType="solid" horizontal /> **Deprecated**: DittoBuilder::new()

  * use Ditto::builder() instead.

  <Icon icon="triangle-exclamation" iconType="solid" horizontal /> **Deprecated**: the store::timeseries module and items (#13902)

  <Icon icon="triangle-exclamation" iconType="solid" horizontal /> **Deprecated**: SiteId, use ditto.presence().graph().local\_peer.peer\_key\_string instead

  ## 4.9.0 Logging Clarity Improvements

  This release comes with a number of logging clarity improvements. The goal of these changes are to make Ditto logs more consumable and actionable for end users. While there are wide ranging changes one of the principal goals of this work is to make our INFO level logs contain the right information to understand the state and health of the Ditto SDK.

  * More information is included when physical connections start and end (such as the type of connection and the remote peer's key)

  * Devices that try to connect to themselves now say "device has connected to itself" instead of an error about the remote site ID being the same as the local peer

  * Authentication client logs have been made more human readable. In particular:

  * Recoverable errors are logged together with information about the recovery actions that are being undertaken

  * Several abbreviations have been replaced with human-readable descriptions

  * Errors are printed using their descriptions rather than by dumping debug representations

  * Abbreviated jargon has been replaced with clearer wording in various log lines

  * "phy ended" has become "physical connection ended"

  * "error getting char" has become "required Ditto BLE characteristic not found"

  * "error getting radio state" has become "error getting Windows Bluetooth radio state"

  * Peer events that represent a transport starting or stopping are now logged with the message "transport started"/"transport ended" rather than as a raw peer\_event=... log

  * Reduced the noisiness of "starting" log lines around Ditto initialization time

  * Noise from long peer keys in logs has been reduced in some places by replacing them with their truncated form

  * Noise from duplicated peer ID/peer key information in replication logs has been reduced by consolidating the information

  * "starting compression and export" is now followed by a "completed export" log at the same level

  * Successful SQLite WAL recovery logs were further lowered from INFO to DEBUG

  ## 4.9.0 Common Changes

  <Icon icon="plus" iconType="solid" horizontal /> **Added:** regexp\_like function in DQL. (#12129)

  <Icon icon="plus" iconType="solid" horizontal /> **Added:** peer\_metadata and identity\_service\_metadata to the small peer info document (#12477)

  <Icon icon="plus" iconType="solid" horizontal /> **Added:** WebSocket connections now send X-DITTO-PEERPUBKEY and X-DITTO-ROUTING-HINT headers as part of the client connect handshake on all platforms except wasm32 (#13171)

  <Icon icon="plus" iconType="solid" horizontal /> **Added:** Small Peer Info now includes information about the current logger configuration (#14317)

  <Icon icon="plus" iconType="solid" horizontal /> **Added:** Permission rules can be written in DQL. (#14563)

  <Icon icon="plus" iconType="solid" horizontal /> **Added:** Ditto logs clearly indicate if a device has established a connection to itself. (#14634)

  <Icon icon="plus" iconType="solid" horizontal /> **Added:** the ability for DQL select statement to produce arbitrary projection lists. (#7979)

  <Icon icon="plus" iconType="solid" horizontal /> **Added:** local subscription info to small peer info (#9412)

  <Icon icon="plus" iconType="solid" horizontal /> **Added:** "device\_disk\_usage" information to small peer info (#9784)

  <Icon icon="plus" iconType="solid" horizontal /> **Added:** "store" information to small peer info (#9785)

  <Icon icon="star" iconType="solid" horizontal /><Icon icon="exclamation" iconType="solid" horizontal /><Icon icon="rotate-reverse" iconType="solid" horizontal /> **Changed:** Internal sync metadata format changed. Peers that downgrade to a previous SDK version after upgrading may require full resynchronization. (#14799)

  <Icon icon="rotate-reverse" iconType="solid" horizontal /> **Changed:** Improved (de)serialization performance and reduced its contribution to the library size (#11545)

  <Icon icon="rotate-reverse" iconType="solid" horizontal /> **Changed:** In updated replication protocol, verification of a received update file no longer requires both peers to use the same approach to subscription hashing. (#12672)

  <Icon icon="rotate-reverse" iconType="solid" horizontal /> **Changed:** Experimental multihop connectivity is more resilient to mesh disruptions (#13648)

  <Icon icon="rotate-reverse" iconType="solid" horizontal /> **Changed:** Synchronization protocol enhanced to reduce the amount of redundant data sent from small peers to big peers. (#13737)

  <Icon icon="rotate-reverse" iconType="solid" horizontal /> **Changed:** Failed certificate verification due to a lagging device clock now results in a clearer error message (#14035)

  <Icon icon="rotate-reverse" iconType="solid" horizontal /> **Changed:** Multicast peer-to-peer transport is no longer deprecated to improve support for environments where mDNS is unavailable (#14188)

  <Icon icon="rotate-reverse" iconType="solid" horizontal /> **Changed:** Replication no longer redundantly re-transmits unchanged subscriptions after eviction. (#14290)

  <Icon icon="rotate-reverse" iconType="solid" horizontal /> **Changed:** truncated peer keys are now logged in lieu of site IDs. (#14362)

  <Icon icon="rotate-reverse" iconType="solid" horizontal /> **Changed:** improved logging in the authentication code to provide more useful error context. (#15038)

  <Icon icon="rotate-reverse" iconType="solid" horizontal /> **Changed:** made the small peer "log request" feature much more responsive (#9777)

  <Icon icon="screwdriver-wrench" iconType="solid" horizontal /> **Fixed:** Windows P2P LAN now can connect to IPv6 peers (#11468)

  <Icon icon="screwdriver-wrench" iconType="solid" horizontal /> **Fixed:** In certain rare cases, resetting the same replication session multiple times could cause failure to converge. (#12616)

  <Icon icon="screwdriver-wrench" iconType="solid" horizontal /> **Fixed:** Internal connection TLS caches are now bounded in size. This prevents a long living peer from holding onto more memory than required. (#13801)

  <Icon icon="screwdriver-wrench" iconType="solid" horizontal /> **Fixed:** small peer info "metadata" is now persisted across app launches. (#13987)

  <Icon icon="screwdriver-wrench" iconType="solid" horizontal /> **Fixed:** Bluetooth peers are handled better when disconnections occur, fixing a possible loop where a device might repeatedly try and fail to connect. (#14018)

  <Icon icon="screwdriver-wrench" iconType="solid" horizontal /> **Fixed:** When replication sessions time out, write transactions on the document store may be blocked for a long period. (#14148)

  <Icon icon="screwdriver-wrench" iconType="solid" horizontal /> **Fixed:** Multicast peer-to-peer transport (non-MDNS) is no longer influenced by TCP listen configuration in DittoTransportConfig (#14187)

  <Icon icon="screwdriver-wrench" iconType="solid" horizontal /> **Fixed:** an issue preventing attachment transfers under high document sync load is now resolved. (#14189)

  <Icon icon="screwdriver-wrench" iconType="solid" horizontal /> **Fixed:** A race condition that could cause attachments to unexpectedly crash under heavy load. (#14342)

  <Icon icon="screwdriver-wrench" iconType="solid" horizontal /> **Fixed:** device name no longer incorrectly defaults to "ditto" in small peer info, when a named device first starts syncing (#14674)

  <Icon icon="screwdriver-wrench" iconType="solid" horizontal /> **Fixed:** presence observers are now less-likely to fire when there is no observable change to presence data. (#14807)

  <Icon icon="screwdriver-wrench" iconType="solid" horizontal /> **Fixed:** Logs report blocked\_by="no blocking transaction" when blocking transaction is known (#14966)

  <Icon icon="screwdriver-wrench" iconType="solid" horizontal /> **Fixed:** In-band authentication data is now cleared on logout. (#15039)

  <Icon icon="screwdriver-wrench" iconType="solid" horizontal /> **Fixed:** switching appIDs now invalidates cached authentication material correctly. (#15040)

  <Icon icon="screwdriver-wrench" iconType="solid" horizontal /> **Fixed:** Transport conditions are now reported for a wider range of failures when starting Bluetooth and mDNS transports. (#8729)

  <Icon icon="screwdriver-wrench" iconType="solid" horizontal /> **Fixed:** documentation for the stopSync() method to clarify that the Ditto store can be used locally after stopping sync. (#8849)

  <Icon icon="screwdriver-wrench" iconType="solid" horizontal /> **Fixed:** Auth Client would hang when cached X.509 was expired. (#15110)

  <Icon icon="triangle-exclamation" iconType="solid" horizontal /> **Deprecated:**

  <Icon icon="exclamation" iconType="solid" horizontal /><Icon icon="bin-recycle" iconType="solid" horizontal /> **Removed:**
</Update>