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pgsql: Fix a performance problem in databases with large numbers of

From: tgl(at)postgresql(dot)org (Tom Lane)
To: pgsql-committers(at)postgresql(dot)org
Subject: pgsql: Fix a performance problem in databases with large numbers of
Date: 2007-01-11 23:06:03
Message-ID: 20070111230603.65CEE9FA31C@postgresql.org (view raw or flat)
Thread:
Lists: pgsql-committers
Log Message:
-----------
Fix a performance problem in databases with large numbers of tables
(or other types of pg_class entry): the function pgstat_vacuum_tabstat,
invoked during VACUUM startup, had runtime proportional to the number of
stats table entries times the number of pg_class rows; in other words
O(N^2) if the stats collector's information is reasonably complete.
Replace list searching with a hash table to bring it back to O(N)
behavior.  Per report from kim at myemma.com.

Back-patch as far as 8.1; 8.0 and before use different coding here.

Modified Files:
--------------
    pgsql/src/backend/postmaster:
        pgstat.c (r1.142 -> r1.143)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/postmaster/pgstat.c.diff?r1=1.142&r2=1.143)

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Subject: pgsql: Fix a performance problem in databases with large numbers of
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Subject: pgsql: Update UNION/INTERSECT/EXCEPT ORDER BY error wording for

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