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Replace RelationOpenSmgr() with RelationGetSmgr().

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The idea behind this patch is to design out bugs like the one fixed
by commit 9d523119f.  Previously, once one did RelationOpenSmgr(rel),
it was considered okay to access rel->rd_smgr directly for some
not-very-clear interval.  But since that pointer will be cleared by
relcache flushes, we had bugs arising from overreliance on a previous
RelationOpenSmgr call still being effective.

Now, very little code except that in rel.h and relcache.c should ever
touch the rd_smgr field directly.  The normal coding rule is to use
RelationGetSmgr(rel) and not expect the result to be valid for longer
than one smgr function call.  There are a couple of places where using
the function every single time seemed like overkill, but they are now
annotated with large warning comments.

Amul Sul, after an idea of mine.

Discussion: https://postgr.es/m/CANiYTQsU7yMFpQYnv=BrcRVqK_3U3mtAzAsJCaqtzsDHfsUbdQ@mail.gmail.com
This commit is contained in:
Tom Lane
2021-07-12 17:01:29 -04:00
parent 5b60cf35f5
commit f10f0ae420
21 changed files with 164 additions and 165 deletions
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15
src/backend/access/heap/rewriteheap.c
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@@ -326,9 +326,8 @@ end_heap_rewrite(RewriteState state)
PageSetChecksumInplace(state->rs_buffer, state->rs_blockno);
RelationOpenSmgr(state->rs_new_rel);
smgrextend(state->rs_new_rel->rd_smgr, MAIN_FORKNUM, state->rs_blockno,
(char *) state->rs_buffer, true);
smgrextend(RelationGetSmgr(state->rs_new_rel), MAIN_FORKNUM,
state->rs_blockno, (char *) state->rs_buffer, true);
}
/*
@@ -339,11 +338,7 @@ end_heap_rewrite(RewriteState state)
* wrote before the checkpoint.
*/
if (RelationNeedsWAL(state->rs_new_rel))
{
/* for an empty table, this could be first smgr access */
RelationOpenSmgr(state->rs_new_rel);
smgrimmedsync(state->rs_new_rel->rd_smgr, MAIN_FORKNUM);
}
smgrimmedsync(RelationGetSmgr(state->rs_new_rel), MAIN_FORKNUM);
logical_end_heap_rewrite(state);
@@ -695,11 +690,9 @@ raw_heap_insert(RewriteState state, HeapTuple tup)
* need for smgr to schedule an fsync for this write; we'll do it
* ourselves in end_heap_rewrite.
*/
RelationOpenSmgr(state->rs_new_rel);
PageSetChecksumInplace(page, state->rs_blockno);
smgrextend(state->rs_new_rel->rd_smgr, MAIN_FORKNUM,
smgrextend(RelationGetSmgr(state->rs_new_rel), MAIN_FORKNUM,
state->rs_blockno, (char *) page, true);
state->rs_blockno++;