CREATE ANALYZE

Description

Customizes an automatic collection task for collecting CBO statistics.

By default, CelerData automatically collects full statistics of a table. It checks for any data updates every 5 minutes. If data change is detected, data collection will be automatically triggered. If you do not want to use automatic full collection, you can set the FE configuration item enable_collect_full_statistic to false and customize a collection task.

Before creating a custom automatic collection task, you must disable automatic full collection (enable_collect_full_statistic = false). Otherwise, custom tasks cannot take effect.

Syntax

-- Automatically collect stats of all databases.
CREATE ANALYZE [FULL|SAMPLE] ALL PROPERTIES (property [,property]);

-- Automatically collect stats of all tables in a database.
CREATE ANALYZE [FULL|SAMPLE] DATABASE db_name
PROPERTIES (property [,property]);

-- Automatically collect stats of specified columns in a table.
CREATE ANALYZE [FULL|SAMPLE] TABLE tbl_name (col_name [,col_name])
PROPERTIES (property [,property]);

Parameter description

Collection type
- FULL: indicates full collection.
- SAMPLE: indicates sampled collection.
- If no collection type is specified, full collection is used by default.
col_name: columns from which to collect statistics. Separate multiple columns with commas (;). If this parameter is not specified, the entire table is collected.
PROPERTIES: custom parameters. If PROPERTIES is not specified, the default settings in fe.conf are used. The properties that are actually used can be viewed via the Properties column in the output of SHOW ANALYZE JOB.

PROPERTIES	Type	Default value	Description
statistic_auto_collect_ratio	FLOAT	0.8	The threshold for determining whether the statistics for automatic collection are healthy. If the statistics health is below this threshold, automatic collection is triggered.
statistics_max_full_collect_data_size	INT	100	The size of the largest partition for automatic collection to collect data. Unit: GB.If a partition exceeds this value, full collection is discarded and sampled collection is performed instead.
statistic_sample_collect_rows	INT	200000	The minimum number of rows to collect.If the parameter value exceeds the actual number of rows in your table, full collection is performed.

Examples

Example 1: Automatic full collection

-- Automatically collect full stats of all databases.
CREATE ANALYZE ALL;

-- Automatically collect full stats of a database.
CREATE ANALYZE DATABASE db_name;

-- Automatically collect full stats of all tables in a database.
CREATE ANALYZE FULL DATABASE db_name;

-- Automatically collect full stats of specified columns in a table.
CREATE ANALYZE TABLE tbl_name(c1, c2, c3);

Example 2: Automatic sampled collection

-- Automatically collect stats of all tables in a database using default settings.
CREATE ANALYZE SAMPLE DATABASE db_name;

-- Automatically collect stats of specified columns in a table, with statistics health and the number of rows to collect specified.
CREATE ANALYZE SAMPLE TABLE tbl_name(c1, c2, c3) PROPERTIES(
   "statistic_auto_collect_ratio" = "0.5",
   "statistic_sample_collect_rows" = "1000000"
);

References

SHOW ANALYZE JOB: view the status of a custom collection task.

DROP ANALYZE: delete a custom collection task.

KILL ANALYZE: cancel a custom collection task that is running.

For more information about collecting statistics for CBO, see Gather statistics for CBO.