ANALYZE_CORRELATIONS

Analyzes the specified tables for pairs of columns that are strongly correlated. ANALYZE_CORRELATIONS stores the 20 pairs with the strongest correlation. ANALYZE_CORRELATIONS also analyzes statistics.

ANALYZE_CORRELATIONS analyzes only pairwise single-column correlations.

For example, state name and country name columns are strongly correlated because the city name usually, but perhaps not always, identifies the state name. The city of Conshohoken is uniquely associated with Pennsylvania, while the city of Boston exists in Georgia, Indiana, Kentucky, New York, Virginia, and Massachusetts. In this case, city name is strongly correlated with state name.

This is a meta-function. You must call meta-functions in a top-level SELECT statement.

Behavior type

Syntax

ANALYZE_CORRELATIONS ('[[[database.]schema.]table ]' [, 'recalculate'] )

Parameters

[database.]schema

Database and schema. The default schema is public. If you specify a database, it must be the current database.

*table-name*

Identifies the table to analyze. If you omit specifying a schema, Vertica uses the current schema search path. If set to an empty string, Vertica analyzes all tables in the current schema.

recalculate

Boolean that specifies whether to analyze correlated columns that were previously analyzed.

Note

Column correlation analysis typically needs to be done only once.

Default: false

Privileges

One of the following:

• Superuser

• User with USAGE privilege on the design schema

Examples

In the following example, ANALYZE_CORRELATIONS analyzes column correlations for all tables in the public schema, even if they currently exist:

=> SELECT ANALYZE_CORRELATIONS ('public.*', 'true');
 ANALYZE_CORRELATIONS
----------------------
                    0
(1 row)