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February 23, 2025
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You can use the UPDATE STATISTICS statement to delete statistics.

Purpose

The UPDATE STATISTICS statement provides a syntax which enables you to delete statistics for a set of index expressions, or for an entire keyspace.

Since the cost-based optimizer uses statistics for cost calculations, deleting statistics for a set of index expressions effectively turns off the cost-based optimizer for queries which utilize predicates on those expressions. Deleting all statistics for a keyspace turns off the cost-based optimizer for all queries referencing that keyspace.

Syntax

update-statistics-delete ::= ( 'UPDATE' 'STATISTICS' 'FOR'? |
                               'ANALYZE' ( 'KEYSPACE' | 'COLLECTION')? )
                               keyspace-ref delete-clause
Syntax diagram: refer to source code listing

For this syntax, UPDATE STATISTICS and ANALYZE are synonyms. The statement must begin with one of these alternatives.

When using the UPDATE STATISTICS keywords, the FOR keyword is optional. Including this keyword makes no difference to the operation of the statement.

When using the ANALYZE keyword, the COLLECTION or KEYSPACE keywords are optional. Including either of these keywords makes no difference to the operation of the statement.

keyspace-ref

Keyspace Reference

delete-clause

DELETE Clause

Keyspace Reference

keyspace-ref ::= keyspace-path | keyspace-partial
Syntax diagram: refer to source code listing
keyspace-path ::= ( namespace ':' )? bucket ( '.' scope '.' collection )?
Syntax diagram: refer to source code listing
keyspace-partial ::= collection
Syntax diagram: refer to source code listing

The simple name or fully-qualified name of the keyspace for which you want to delete statistics. Refer to the CREATE INDEX statement for details of the syntax.

DELETE Clause

delete-clause ::= 'DELETE' ( delete-expr | delete-all )
Syntax diagram: refer to source code listing

The DELETE clause enables you to provide a comma-separated list of index expressions for which you want to delete statistics, or to specify that you want to delete all statistics for the keyspace.

delete-expr

Delete Expressions

delete-all

Delete All Statistics

Delete Expressions

delete-expr ::= 'STATISTICS'? '(' index-key ( ',' index-key )* ')'
Syntax diagram: refer to source code listing

Constraint: if you used the UPDATE STATISTICS keywords at the beginning of the statement, you may not use the STATISTICS keyword in this clause.

Conversely, if you used the ANALYZE keyword at the beginning of the statement, you must include the STATISTICS keyword in this clause.

index-key

[Required] The expression for which you want to delete statistics. This may be any expression that is supported as an index key, including, but not limited to:

Delete All Statistics

delete-all ::= 'ALL' | 'STATISTICS'
Syntax diagram: refer to source code listing

Constraint: If you used the UPDATE STATISTICS keywords at the beginning of the statement, you must use the ALL keyword in this clause.

Conversely, if you used the ANALYZE keyword at the beginning of the statement, you must use the STATISTICS keyword in this clause.

Result

The statement returns an empty array.

Examples

To try the examples in this section, set the query context to the inventory scope in the travel sample dataset. For more information, see Query Context.

Example 1. Delete statistics with UPDATE STATISTICS
UPDATE STATISTICS FOR hotel
DELETE (city, country, free_breakfast);
Example 2. Delete statistics with ANALYZE
ANALYZE KEYSPACE hotel
DELETE STATISTICS (city, country, free_breakfast);

This query is equivalent to the query in Example 1.

Example 3. Delete all statistics with UPDATE STATISTICS
UPDATE STATISTICS FOR airport DELETE ALL;
Example 4. Delete all statistics with ANALYZE
ANALYZE KEYSPACE airport DELETE STATISTICS;

This query is equivalent to the query in Example 3.