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Improve C comments about backend variables set by pg_upgrade_support

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functions.
This commit is contained in:
Bruce Momjian
2011-01-06 22:44:57 -05:00
parent 7f40e30309
commit 46d28820b6
7 changed files with 43 additions and 9 deletions
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22
contrib/pg_upgrade/pg_upgrade.c
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@ -7,6 +7,28 @@
* contrib/pg_upgrade/pg_upgrade.c
*/
/*
* To simplify the upgrade process, we force certain system items to be
* consistent between old and new clusters:
*
* We control all assignments of pg_class.relfilenode so we can keep the
* same relfilenodes for old and new files. The only exception is
* pg_largeobject, pg_largeobject_metadata, and its indexes, which can
* change due to a cluster, reindex, or vacuum full. (We don't create
* those so have no control over their oid/relfilenode values.)
*
* While pg_class.oid and pg_class.relfilenode are intially the same, they
* can diverge due to cluster, reindex, or vacuum full. The new cluster
* will again have matching pg_class.relfilenode and pg_class.oid values,
* but based on the new relfilenode value, so the old/new oids might
* differ.
*
* We control all assignments of pg_type.oid because these are stored
* in composite types.
*/
#include "pg_upgrade.h"
#ifdef HAVE_LANGINFO_H