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
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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 | |
delete-clause |
Keyspace Reference
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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
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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-all |
Delete Expressions
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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:
|
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.