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pgsql: Fix a performance problem in databases with large numbers of - Mailing list pgsql-committers

From tgl@postgresql.org (Tom Lane)
Subject pgsql: Fix a performance problem in databases with large numbers of
Date
Msg-id 20070111230609.918BF9FB1DD@postgresql.org
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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.

Tags:
----
REL8_2_STABLE

Modified Files:
--------------
    pgsql/src/backend/postmaster:
        pgstat.c (r1.140 -> r1.140.2.1)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/postmaster/pgstat.c.diff?r1=1.140&r2=1.140.2.1)

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