diff options
author | Magnus Hagander | 2007-05-13 16:04:22 +0000 |
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committer | Magnus Hagander | 2007-05-13 16:04:22 +0000 |
commit | 7ee0498772e11631f9da2d8dd68f62843f7d651b (patch) | |
tree | c66025bf242f90f9bc683a8345d737952314e1bd | |
parent | e449e1912485dd3f1dc74471237f79e5e56e7518 (diff) |
Document that CLUSTER breaks MVCC visibility rules.
(Not needed in cvs head, because CLUSTER itself is fixed there)
Heikki Linnakangas
-rw-r--r-- | doc/src/sgml/ref/cluster.sgml | 13 |
1 files changed, 12 insertions, 1 deletions
diff --git a/doc/src/sgml/ref/cluster.sgml b/doc/src/sgml/ref/cluster.sgml index 12f18623d77..756e1bc569b 100644 --- a/doc/src/sgml/ref/cluster.sgml +++ b/doc/src/sgml/ref/cluster.sgml @@ -1,5 +1,5 @@ <!-- -$Header: /cvsroot/pgsql/doc/src/sgml/ref/cluster.sgml,v 1.30 2003/11/02 12:59:54 petere Exp $ +$Header: /cvsroot/pgsql/doc/src/sgml/ref/cluster.sgml,v 1.30.2.1 2007/05/13 16:04:22 mha Exp $ PostgreSQL documentation --> @@ -100,6 +100,17 @@ CLUSTER <title>Notes</title> <para> + <command>CLUSTER</command> loses all visibility information of tuples, + which makes the table look empty to any snapshot that was taken + before the <command>CLUSTER</command> command finished. That makes + <command>CLUSTER</command> unsuitable for applications where + transactions that access the table being clustered are run concurrently + with <command>CLUSTER</command>. This is most visible with serializable + transactions, because they take only one snapshot at the beginning of the + transaction, but read-committed transactions are also affected. + </para> + + <para> In cases where you are accessing single rows randomly within a table, the actual order of the data in the table is unimportant. However, if you tend to access some |