SI messages now include the relevant database OID, so that operations
in one database do not cause useless cache flushes in backends attached
to other databases. Declare SI messages properly using a union, to
eliminate the former assumption that Oid is the same size as int or Index.
Rewrite the nearly-unreadable code in inval.c, and document it better.
Arrange for catcache flushes at end of command/transaction to happen before
relcache flushes do --- this avoids loading a new tuple into the catcache
while setting up new relcache entry, only to have it be flushed again
immediately.
(WAL logging for this is not done yet, however.) Clean up a number of really
crufty things that are no longer needed now that DROP behaves nicely. Make
temp table mapper do the right things when drop or rename affecting a temp
table is rolled back. Also, remove "relation modified while in use" error
check, in favor of locking tables at first reference and holding that lock
throughout the statement.
inval.c thought it could safely use the catcache to look up the OIDs of
system relations. Not good, considering that inval.c could be called
during catcache loading, if a shared-inval message arrives. Rip out the
lookup logic and instead use the known OIDs from pg_class.h.
The diff looks so simple and easy. But to find it wasn't fun.
It must have been there for a long time. What happened:
When a tuple in one of some central catalogs was updated, the
referenced relation got flushed, so it would be reopened on
the next access (to reflect new triggers, rules and table
structure changes into the relation cache).
Some data (the tupleDescriptor e.g.) is used in the system
cache too. So when a relation is subject to the system cache,
this must know too that a cached system relation got flushed
because the tupleDesc data gets freed during the flush!
For the GRANT/REVOKE on pg_class it was slightly different.
There is some local data in inval.c that gets initialized on
the first invalidation of a tuple in some central catalogs.
This needs a SysCache lookup in pg_class. But when the first
of all commands is a GRANT on pg_class, exactly the needed
tuple is the one actually invalidated. So I added little code
snippets that the initialization of the local variables in
inval.c will already happen during InitPostgres().
Bruce Momjian
Tom Lane
Hiroshi Inoue
Marc G. Fournier