Horton

ALTER TYPE 1: recheck index-based constraints

Noah Misch <noah@leadboat.com>

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From: Noah Misch <noah@leadboat.com>
To: pgsql-hackers@postgresql.org
Date: 2011-01-09T22:00:23Z
Lists: pgsql-hackers

Commits

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  1. Work around deadlock problems with VACUUM FULL/CLUSTER on system catalogs,

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When ALTER TABLE rewrites a table, it reindexes, but the reindex does not
revalidate UNIQUE/EXCLUDE constraints.  This behaves badly in cases like this,
neglecting to throw an error on the new UNIQUE violation:

CREATE TABLE t (c numeric UNIQUE);
INSERT INTO t VALUES (1.1),(1.2);
ALTER TABLE t ALTER c TYPE int;

The comment gave a reason for skipping the checks: it would cause deadlocks when
we rewrite a system catalog.  So, this patch changes things to only skip the
check for system catalogs.