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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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14
src/backend/access/gist/gistbuild.c
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@ -409,8 +409,7 @@ gist_indexsortbuild(GISTBuildState *state)
* replaced with the real root page at the end.
*/
page = palloc0(BLCKSZ);
RelationOpenSmgr(state->indexrel);
smgrextend(state->indexrel->rd_smgr, MAIN_FORKNUM, GIST_ROOT_BLKNO,
smgrextend(RelationGetSmgr(state->indexrel), MAIN_FORKNUM, GIST_ROOT_BLKNO,
page, true);
state->pages_allocated++;
state->pages_written++;
@ -450,10 +449,9 @@ gist_indexsortbuild(GISTBuildState *state)
gist_indexsortbuild_flush_ready_pages(state);
/* Write out the root */
RelationOpenSmgr(state->indexrel);
PageSetLSN(pagestate->page, GistBuildLSN);
PageSetChecksumInplace(pagestate->page, GIST_ROOT_BLKNO);
smgrwrite(state->indexrel->rd_smgr, MAIN_FORKNUM, GIST_ROOT_BLKNO,
smgrwrite(RelationGetSmgr(state->indexrel), MAIN_FORKNUM, GIST_ROOT_BLKNO,
pagestate->page, true);
if (RelationNeedsWAL(state->indexrel))
log_newpage(&state->indexrel->rd_node, MAIN_FORKNUM, GIST_ROOT_BLKNO,
@ -562,8 +560,6 @@ gist_indexsortbuild_flush_ready_pages(GISTBuildState *state)
if (state->ready_num_pages == 0)
return;
RelationOpenSmgr(state->indexrel);
for (int i = 0; i < state->ready_num_pages; i++)
{
Page page = state->ready_pages[i];
@ -575,7 +571,8 @@ gist_indexsortbuild_flush_ready_pages(GISTBuildState *state)
PageSetLSN(page, GistBuildLSN);
PageSetChecksumInplace(page, blkno);
smgrextend(state->indexrel->rd_smgr, MAIN_FORKNUM, blkno, page, true);
smgrextend(RelationGetSmgr(state->indexrel), MAIN_FORKNUM, blkno, page,
true);
state->pages_written++;
}
@ -860,7 +857,8 @@ gistBuildCallback(Relation index,
*/
if ((buildstate->buildMode == GIST_BUFFERING_AUTO &&
buildstate->indtuples % BUFFERING_MODE_SWITCH_CHECK_STEP == 0 &&
effective_cache_size < smgrnblocks(index->rd_smgr, MAIN_FORKNUM)) ||
effective_cache_size < smgrnblocks(RelationGetSmgr(index),
MAIN_FORKNUM)) ||
(buildstate->buildMode == GIST_BUFFERING_STATS &&
buildstate->indtuples >= BUFFERING_MODE_TUPLE_SIZE_STATS_TARGET))
{