> ## 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.

# EXPLAIN

> DQL language syntax for displaying the execution plan produced by the query planner for a statement.

You can preface any DQL statement with EXPLAIN to instruct the query engine to return only the execution plan for the statement.  This takes the form of a series of operators presented as JSON objects which represent the various component actions the planner has determined as necessary in order to execute the statement.

<Note>The statement isn't executed when using EXPLAIN, only the parsing and planning stages take place.</Note>

<img src="https://mintcdn.com/ditto-248bc0d1/pf3IlRElveI85RoM/images/dql/Explain.svg?fit=max&auto=format&n=pf3IlRElveI85RoM&q=85&s=9c3e2a81dbcffb96acb2e46d269c0b9c" alt="EXPLAIN Syntax Diagram" width="217" height="77" data-path="images/dql/Explain.svg" />

Example:

```sql DQL theme={null}
EXPLAIN SELECT test.* FROM test;
```

produces:

```text theme={null}
{
  "plan": {
    "#operator": "sequence",
    "children": [
      {
        "#operator": "scan",
        "alias": "test",
        "collection": "test",
        "datasource": "default",
        "descriptor": {
          "path": {
            "full_scan": {}
          }
        }
      },
      {
        "#operator": "projection",
        "projections": [
          {
            "expression": "`test`",
            "wildcard": true
          }
        ]
      }
    ]
  }
}
```

A query plan is read from top to bottom to follow the flow of data through it.  In the above example the first action is to scan the collection with a full collection scan (see [Access paths](/dql/access-paths)) then project the entire document.  In the example below an index scan is used to located the data which matches "field1 = 1", is then filtered (the index scan filter is re-applied along with application of the other filter ("field2 = 2")), is then grouped, projected and the results ordered (the final projection is just a second part to the projection present when necessary in certain plans):

```sql DQL theme={null}
EXPLAIN
SELECT field3,count(*) the_count
FROM test
WHERE (field1 = 1 AND field2 = 2)
GROUP BY field3
ORDER BY the_count DESC;
```

```text theme={null}
{
  "plan": {
    "#operator": "sequence",
    "children": [
      {
        "#operator": "index_scan",
        "alias": "test",
        "collection": "test",
        "datasource": "default",
        "desc": {
          "index": "ix_f1",
          "spans": [
            {
              "index_key": {
                "direction": "asc",
                "include_missing": true,
                "key": [
                  "field1"
                ]
              },
              "range": {
                "high": {
                  "included": true,
                  "value": 1
                },
                "low": {
                  "included": true,
                  "value": 1
                }
              }
            }
          ]
        }
      },
      {
        "#operator": "filter",
        "condition": "((`test`.`field1` = 1) AND (`test`.`field2` = 2))"
      },
      {
        "#operator": "groupBy",
        "aggregates": [
          {
            "expr": "true",
            "name": "count(true)"
          }
        ],
        "keys": [
          {
            "alias": "$$(group_by_key_1)$$",
            "expression": "`test`.`field3`"
          }
        ]
      },
      {
        "#operator": "projection",
        "projections": [
          {
            "alias": "field3",
            "expression": ".`$$(group_by_key_1)$$`"
          },
          {
            "alias": "the_count",
            "expression": "count(true)"
          }
        ]
      },
      {
        "#operator": "sort",
        "orderBy": [
          {
            "direction": "desc",
            "key": ".`$$(projection)$$`.`the_count`"
          }
        ]
      },
      {
        "#operator": "final_projection"
      }
    ]
  }
}
```