EVICT

EVICT FROM your_collection_name
WHERE [condition]
LIMIT [limit]
OFFSET [offset]
ORDER BY [order by]

In this syntax:

• your_collection_name is the name of the collection from which you want to retrieve the data.
• [condition] represents the condition or criteria that determine which documents should be evicted from the local peer.
• [limit] represents the maximum number of documents that should be evicted
• [offset] represents the offset from 0 that should be used for the eviction query, in practice this should be rarely used
• [order by] represents the path within a document to use to order the dataset and order (ASC or DESC)

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Examples Deleting Documents

Here, documents from the cars collection that have the document ID 123 get removed from the Ditto store:

EVICT FROM cars
WHERE _id = '123'

As another example, the following snippet, once executed, results in the deletion of documents with timestamps greater than a certain value:

EVICT FROM cars
WHERE some_time_stamp > 1699888298000

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Removing Fields from Documents

To remove a specific field from a document, use an UPDATE statement to tombstone that field. A tombstone is a flag signaling to remote peers that the data type has been removed. See: UPDATE

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Removing Data from Ditto Server

EVICT can be enabled for Ditto Server by request. Please contact us if you’d like to use this feature.

Note that any data evicted from Ditto Server will reappear if it exists in any Small Peer devices connected to Ditto Server.

To permanently remove the data, you must first ensure the data is no longer subscribed to, and is already evicted, by any connected Small Peers. See Developing an Eviction Strategy for more.

Alternatively, data can be tombstoned from Ditto Server using the legacy API. See: Writing: HTTP (Legacy).

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Developing an Eviction Strategy

Removing data from a distributed database is a difficult problem, and memory management requires careful consideration of both subscriptions and evictions.

To learn more about our recommended strategies, see DELETE.