ANALYZE_STATISTICS

ANALYZE_STATISTICS is an alias of the function ANALYZE_HISTOGRAM, which is no longer documented.

Collects and aggregates data samples and storage information from all nodes that store projections associated with the specified table. By default, Vertica analyzes multiple columns in a single-query execution plan, depending on resource limits. Such multi-column analysis facilitates the following objectives:

  • Reduce plan execution latency.
  • Speed up analysis of relatively small tables with many columns.

Vertica writes statistics to the database catalog. The query optimizer uses this collected data to create query plans. Without this data, the query optimizer assumes uniform distribution of data values and equal storage usage for all projections.

You can cancel statistics collection with CTRL+C or by calling INTERRUPT_STATEMENT.

Syntax

ANALYZE_STATISTICS ('[[[database.]schema.]table]' [, 'column‑list' [, percent ]]  )

Returns

0—Success

If an error occurs, refer to vertica.log for details.

Parameters

[database.]schema

Specifies a schema, by default public. If schema is any schema other than public, you must supply the schema name. For example:

myschema.thisDbObject

If you specify a database, it must be the current database.
table

Table on which to collect data. If set to an empty string, Vertica collects statistics for all database tables and their projections.
column‑list

Comma-delimited list of columns in table, typically predicate columns. Vertica narrows the scope of the data collection to the specified columns.

If you alter a table to add a column and populate its contents with either default or other values, call ANALYZE_STATISTICS on this column to get the most current statistics.

percent

A float value between 0 and 100 that specifies what percentage of data to read from disk (not the amount of data to analyze). If you omit this argument, Vertica sets the percentage to 10.

Analyzing more than 10 percent disk space takes proportionally longer to process, but produces a higher level of sampling accuracy.

Privileges

Non-superuser:

  • Schema: USAGE
  • Table: One of INSERT, DELETE, or UPDATE

Restrictions

  • Vertica supports ANALYZE_STATISTICS on local and global temporary tables. In both cases, you can obtain statistics only on tables that are created with the option ON COMMIT PRESERVE ROWS. Otherwise, Vertica deletes table content on committing the current transaction, so no table data is available for analysis.
  • Vertica collects no statistics from the following projections:
    • Live aggregate and Top-K projections
    • Projections that are defined to include an SQL function within an expression
  • Vertica collects no statistics on columns of ARRAY or SET types.

See Also