STATSCACHE System Table Description

Description

A pseudo table generated to show statistics cached for use by the NuoDB query optimizer. Rows in SYSTEM.STATSCACHE represent either table or index objects in the database.

Client applications should never contain code that accesses SYSTEM pseudo tables as they are subject to, and furthermore likely to, change from release to release.

Fields

Field Type Description

ID

bigint

The database ID for the table or index object.

VERSION

bigint

Index statistics are versioned and this field represents the version number.

TYPE

string

Currently this is either index or table.

NAME

string

The name of either the index or the table.

VALID

boolean

True if valid and usable by the query optimizer.

CARDINALITY

bigint

The cardinality of the index or table.

DISTINCTCOUNT

bigint

The number of distinct keys in the index, null for tables.

AVERAGEKEYLENGTH

double

The average length of a key in the index, null for tables.

HISTOGRAMCOUNT

bigint

The number of histogram buckets for the index, null for tables.

SPAN

string

The partitions that are spanned by the statistics. Where tables are not partitioned, or where statistics span all partitions, this column does not populate.

Indexes

None