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                              WORKLOG TASK
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TASK...........: Collect engine independent statistics on table columns and indexes to
		store it in persistent system tables
CREATION DATE..: Wed, 04 Jan 2012, 04:11
SUPERVISOR.....: 
IMPLEMENTOR....: Igor
COPIES TO......: Igor Knielsen Monty Psergey Sanja Sergei Timour Wlad
CATEGORY.......: Server-BackLog
TASK ID........: 248 (http://askmonty.org/worklog/?tid=248)
VERSION........: Server-5.5
STATUS.........: Assigned
PRIORITY.......: 60
WORKED HOURS...: 0
ESTIMATE.......: 120 (hours remain)
ORIG. ESTIMATE.: 120

PROGRESS NOTES:



DESCRIPTION:

In a special mode the ANALYZE command will collect statistics on table
cardinality, table columns and table indexes. This statistics will be stored in
system tables table_stat, column_stat and index_stat.

For any database table the system table table_stat will contain the number of
rows in the table.
For any table column the system table column_stat will contain min and max value,
the share of null values, the average length of a column value, and the the
average frequency of the column values.
For any index defined on a database table the system table index_stat will
contain number of records per every key prefix.

This task will be implemented in 3 steps:
1. A pure back-port of the WL#4777 from mysql-5.4 code line will be performed.
2. New possibility to collect statistics only on specified columns and/or
indexes will be added.
3. A new possibility to scan only a certain percentage of the table records in a
pseudo-random manner will be added.

The collected statistics is supposed to be used by the optimizer, but this will
be an objective of some other task.


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