MariaDB starting with 10.0.1

The mysql.column_stats table was introduced as part of the Engine-independent table statistics feature implemented in MariaDB 10.0.1.

The mysql.column_stats table is one of three tables storing data used for Engine-independent table statistics added in MariaDB 10.0.1. The others are mysql.table_stats and mysql.index_stats.The histogram fields were added in MariaDB 10.0.2 as part of the Histogram-based Statistics feature.

Note that statistics for blob and text columns are not collected. If explicitly specified, a warning is returned.

The table contains the following fields:

FieldTypeNullKeyDefaultDescription
db_namevarchar(64)NOPRINULLDatabase the table is in.
table_namevarchar(64)NOPRINULLTable name.
column_namevarchar(64)NOPRINULLName of the column.
min_valuevarchar(255)YESNULLMinimum value in the table (in text form).
max_valuevarchar(255)YESNULLMaximum value in the table (in text form).
nulls_ratiodecimal(12,4)YESNULLFraction of NULL values (0 - no NULLs, 0.5 - half values are NULLs, 1 - all values are NULLs).
avg_lengthdecimal(12,4)YESNULLAverage length of column value, in bytes. Counted as if one ran SELECT AVG(LENGTH(col)). This doesn't count NULL bytes, assumes endspace removal for CHAR(n), etc.
avg_frequencydecimal(12,4)YESNULLAverage number of records with the same value
hist_sizetinyint(3) unsignedYESNULLHistogram size in bytes, from 0-255.
hist_typeenum('SINGLE_PREC_HB', 'DOUBLE_PREC_HB')YESNULLHistogram type. See the histogram_type system variable.
histogramvarbinary(255)YESNULL

It is possible to manually update the table. See Manual updates to statistics tables for details.

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