From: | tgl(at)postgresql(dot)org (Tom Lane) |
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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 |
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Lists: | pgsql-committers |
Log Message:
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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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