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From "Mamta A. Satoor (JIRA)" <derby-...@db.apache.org>
Subject [jira] Commented: (DERBY-737) SYSCS_UTIL.SYSCS_COMPRESS_TABLE should create statistics if they do not exist
Date Thu, 05 Oct 2006 06:24:20 GMT
    [ http://issues.apache.org/jira/browse/DERBY-737?page=comments#action_12440039 ] 
            
Mamta A. Satoor commented on DERBY-737:
---------------------------------------

I am slightly confused by the 1st line in the description of this Jira entry. It says "There
must be an entry in the SYSSTATISTICS table in order for the cardinality statistics in SYSSTATISTICS
to be created with SYSCS_UTIL.SYSCS_COMPRESS_TABLE "
Shouldn't it read "There must be an entry in the SYSSTATISTICS table in order for the cardinality
statistics in SYSSTATISTICS to be *updated* with SYSCS_UTIL.SYSCS_COMPRESS_TABLE "? The new
sentence I am suggesting describes the current behavior of Derby which is that currently,
SYSCS_UTIL.SYSCS_COMPRESS_TABLE can update statistics for indexes that already have rows in
SYSSTATISTICS table. If there is no row for an index in SYSSTATISTICS table, then no statistics
will be generated for that index.

With this Jira, we want to change Derby behavior such that if there is no row for an index
in SYSSTATISTICS table, then at the time of SYSCS_UTIL.SYSCS_COMPRESS_TABLE, we should create
a row for that index into SYSSTATISTICS table(provided that there is data in the table on
which SYSCS_UTIL.SYSCS_COMPRESS_TABLE is getting run, no?) . If a row already exists for an
index, then SYSCS_UTIL.SYSCS_COMPRESS_TABLE already does the job of updating the statistics
for that index.

I am interested in working on this issue and want to be clear that I understand the current
behavior and the expected new behavior.

> SYSCS_UTIL.SYSCS_COMPRESS_TABLE should create statistics if they do not exist
> -----------------------------------------------------------------------------
>
>                 Key: DERBY-737
>                 URL: http://issues.apache.org/jira/browse/DERBY-737
>             Project: Derby
>          Issue Type: Improvement
>          Components: SQL
>    Affects Versions: 10.0.2.0, 10.0.2.1, 10.1.1.0, 10.1.1.1, 10.1.1.2, 10.1.2.0, 10.1.2.1,
10.2.1.6, 10.1.3.0, 10.1.2.2, 10.0.2.2
>            Reporter: Kathey Marsden
>            Priority: Minor
>
> There must be an entry in the SYSSTATISTICS table in order for the cardinality statistics
in SYSSTATISTICS to be created with SYSCS_UTIL.SYSCS_COMPRESS_TABLE 
> SYSCS_UTIL.SYSCS_COMPRESS_TABLE  should create statistics if they don't exist.  The only
way to create them if the index was created on an empty table, seems to be to drop and recreate
the index after the table has been loaded.
> The documentation will also need updating if this change is made.
> http://db.apache.org/derby/docs/10.1/tuning/ctunstats57373.html

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