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().
Attached is the patch to fix the warning messages from my code. I also
fixed one which wasn't my code. Apart from the usual warnings about the
bison/yacc generated code I only have one other warning message. This
is in gramm.y around line 2234. I wasn't sure of the fix.
I've also replaced all the calls to free() in gramm.y to calls to
pfree(). Without these I was getting backend crashes with GRANT. This
might already have been fixed.
