SingleStore DB

information_schema.MV_QUERY_PROSPECTIVE_HISTOGRAMS

This view contains information about columns which were used in queries where a histogram could have been utilized, but did not have histograms. This is similar to MV_PROSPECTIVE_HISTOGRAMS, but MV_QUERY_PROSPECTIVE_HISTOGRAMS displays one row per column per query, while MV_PROSPECTIVE_HISTOGRAMS displays one row per column, and aggregates over all queries.

This view counts over all queries (rows) in the in-memory plancache in order to distinguish which of these contain applicable columns. This can be useful for examining which columns included in these queries should have autostats enabled for the future. See further information about this, and how to set autostats in Statistics Sampling and ANALYZE.

Column Name

Description

ACTIVITY_NAME

The ID of the query.

DATABASE_NAME

The name of the related database.

TABLE_NAME

The name of the related table.

COLUMN_NAME

The name of a given column for which a prospective histogram has been identified.

USAGE_COUNT

The number of times the column was used where a histogram could have been utilized, counting once per occurrence of the table in the query.