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.
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Fields
| Field | Type | Description |
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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. |
HISTOGRAMSPAN |
string |
The partition information covered by the cached histograms. |
SCALARSTATSSPAN |
string |
The partition information covered by the cached scalar stats. |
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. |
CARDINALITY, DISTINCTCOUNT, AVERAGEKEYLENGTH, and HISTOGRAMCOUNT fields are not used in Table Statistics (Stats v3).
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