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Cluster fixup.

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Bruce Momjian
1998-03-14 22:55:21 +00:00
parent 3674ccdf95
commit 006fd9253f
1 changed files with 7 additions and 6 deletions
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13
src/man/cluster.l
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@ -1,6 +1,6 @@
.\" This is -*-nroff-*- .\" This is -*-nroff-*-
.\" XXX standard disclaimer belongs here.... .\" XXX standard disclaimer belongs here....
.\" $Header: /cvsroot/pgsql/src/man/Attic/cluster.l,v 1.5 1998/03/14 21:57:56 momjian Exp $ .\" $Header: /cvsroot/pgsql/src/man/Attic/cluster.l,v 1.6 1998/03/14 22:55:21 momjian Exp $
.TH CLUSTER SQL 01/23/93 PostgreSQL PostgreSQL .TH CLUSTER SQL 01/23/93 PostgreSQL PostgreSQL
.SH NAME .SH NAME
cluster - give storage clustering advice to Postgres cluster - give storage clustering advice to Postgres
@ -48,11 +48,12 @@ unordered, the entries are on random pages, so there is one disk page
retrieved for every row moved. PostgreSQL has a cache, but the majority retrieved for every row moved. PostgreSQL has a cache, but the majority
of a big table will not fit in the cache. of a big table will not fit in the cache.
.PP .PP
Another way is to use SELECT ... INTO TABLE temp FROM ... This uses the Another way is to use SELECT ... INTO TABLE temp FROM ...ORDER BY ...
PostgreSQL sorting code, and is much faster for unordered data. You This uses the PostgreSQL sorting code in ORDER BY to match the index,
then drop the old table, use ALTER TABLE RENAME to rename 'temp' to the and is much faster for unordered data. You then drop the old table, use
old name, and recreate the indexes. From then on, CLUSTER should be ALTER TABLE RENAME to rename 'temp' to the old name, and recreate the
fast because most of the heap data is ordered. indexes. From then on, CLUSTER should be fast because most of the heap
data has been already ordered.
.SH EXAMPLE .SH EXAMPLE
.nf .nf
/* /*