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Simplify pg_upgrade C comment about what is preserved.

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This commit is contained in:
Bruce Momjian 2011-01-07 22:46:41 -05:00
parent f75383e6e8
commit 3095643d37
1 changed files with 6 additions and 12 deletions
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18
contrib/pg_upgrade/pg_upgrade.c
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@ -15,22 +15,16 @@
* oids are the same between old and new clusters. This is important
* because toast oids are stored as toast pointers in user tables.
*
* The only place where old/new relfilenode might not match is
* pg_largeobject, pg_largeobject_metadata, and its indexes,
* which can change their relfilenode values due to a cluster, reindex,
* or vacuum full. (We don't create those so have no control over their
* new relfilenode values.)
*
* FYI, while pg_class.oid and pg_class.relfilenode are intially the same
* in a cluster, but 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 old relfilenode value, so the
* old/new oids might differ.
* in a cluster, but they can diverge due to CLUSTER, REINDEX, or VACUUM
* FULL. The new cluster will have matching pg_class.oid and
* pg_class.relfilenode values and be based on the old oid value. This can
* cause the old and new pg_class.relfilenode values to differ.
*
* We control all assignments of pg_type.oid because these oid are stored
* We control all assignments of pg_type.oid because these oids are stored
* in user composite type values.
*
* We control all assignments of pg_enum.oid because these oid are stored
* We control all assignments of pg_enum.oid because these oids are stored
* in user tables as enum values.
*/