Update Statistics for Multiple Indexes
- Enterprise Edition
- Couchbase Server 7.0
You can use the
UPDATE STATISTICSstatement to gather statistics for multiple indexes at once.
UPDATE STATISTICS statement provides a syntax which enables you to analyze multiple indexes at once.
With this syntax, the statement gathers statistics for all the index key expressions from all specified indexes.
This provides a shorthand so that you do not need to list all the index key expressions explicitly.
If the same index expression is included in multiple indexes, duplicate index expressions are removed, so each index expression is only analyzed once.
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
KEYSPACE keywords are optional.
Including either of these keywords makes no difference to the operation of the statement.
keyspace-partial ::= collection
The simple name or fully-qualified name of the keyspace on which the indexes are built. Refer to the CREATE INDEX statement for details of the syntax.
indexes-clause ::= INDEX ( '(' index-name [ ',' index-name ]* | subquery-expr ')' | ALL )
For this syntax, the
INDEX clause enables you to specify a comma-separated list of index names, a subquery which returns an array of index names, or all the indexes in the specified keyspace.
(Required) A unique name that identifies an index.
subquery-expr ::= '(' select ')'
Use parentheses to specify a subquery.
index-using ::= USING GSI
In Couchbase Server 6.5 and later, the index type for a secondary index must be Global Secondary Index (GSI).
USING GSI keywords are optional and may be omitted.
index-with ::= WITH expr
WITH clause to specify additional options.
An object with the following properties:
[Optional] An integer specifying the sample size to use for distribution statistics. A minimum sample size is also calculated. If the specified sample size is smaller than the minimum sample size, the minimum sample size is used instead.
[Optional] A float representing the percentage of documents to store in each distribution bin. If omitted, the default value is
1.0, meaning each distribution bin contains 1% of the documents, and therefore 100 bins are required. The minimum resolution is
0.02(5000 distribution bins) and the maximum is
5.0(20 distribution bins).
[Optional] A number representing a duration in seconds. The command times out when this timeout period is reached. If omitted, a default timeout value is calculated based on the number of samples used.
[Optional] Only applies when processing multiple index expressions at once. If there is a large number of index expressions to process, the cost-based optimizer deals with them in batches. This option is an integer specifying the maximum number of index expressions in each batch. If omitted, the default value is
10. You can specify a different value based on the memory availability of the system. Note that when index expressions are processed in batches, the
update_statistics_timeoutvalue (above) applies to each batch.
Refer to Distribution Statistics for more information on sample size and resolution.
UPDATE STATISTICS FOR `travel-sample`.inventory.airport INDEX (def_inventory_airport_faa, def_inventory_airport_city);
ANALYZE KEYSPACE `travel-sample`.inventory.airport INDEX (def_inventory_airport_faa, def_inventory_airport_city);
This query is equivalent to the query in Example 1.
UPDATE STATISTICS FOR `travel-sample`.inventory.airport INDEX (( (1) SELECT RAW name (2) FROM system:indexes WHERE state = "online" AND `using` = "gsi" (3) AND bucket_id = "travel-sample" AND scope_id = "inventory" AND keyspace_id = "airport" ));
|1||One set of parentheses delimits the whole group of index terms, and the other set of parentheses delimits the subquery, leading to a double set of parentheses.|
ANALYZE KEYSPACE `travel-sample`.inventory.airport INDEX (( SELECT RAW name FROM system:indexes WHERE state = "online" AND `using` = "gsi" AND bucket_id = "travel-sample" AND scope_id = "inventory" AND keyspace_id = "airport" ));
This query is equivalent to the query in Example 4.
UPDATE STATISTICS FOR `travel-sample`.inventory.airport INDEX ALL;
ANALYZE KEYSPACE `travel-sample`.inventory.airport INDEX ALL;
This query is equivalent to the query in Example 5.