SingleStore DB

information_schema.MV_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 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

Note that this view displays the columns that did not have histograms at the time each plan was compiled, so it will continue to display such columns even after histograms are collected. You can filter to find only the columns that currently do not have histograms by joining against information_schema.OPTIMIZER_STATISTICS, looking for columns where RANGE_STATS is false.

Column Name

Description

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 in queries where a histogram could have been utilized, counting once per query per occurrence of the table.