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Fix up rickety handling of relation-truncation interlocks.
Move rd_targblock, rd_fsm_nblocks, and rd_vm_nblocks from relcache to the smgr relation entries, so that they will get reset to InvalidBlockNumber whenever an smgr-level flush happens. Because we now send smgr invalidation messages immediately (not at end of transaction) when a relation truncation occurs, this ensures that other backends will reset their values before they next access the relation. We no longer need the unreliable assumption that a VACUUM that's doing a truncation will hold its AccessExclusive lock until commit --- in fact, we can intentionally release that lock as soon as we've completed the truncation. This patch therefore reverts (most of) Alvaro's patch of 2009-11-10, as well as my marginal hacking on it yesterday. We can also get rid of assorted no-longer-needed relcache flushes, which are far more expensive than an smgr flush because they kill a lot more state. In passing this patch fixes smgr_redo's failure to perform visibility-map truncation, and cleans up some rather dubious assumptions in freespace.c and visibilitymap.c about when rd_fsm_nblocks and rd_vm_nblocks can be out of date.
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@@ -8,7 +8,7 @@
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* Portions Copyright (c) 1994, Regents of the University of California
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*
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* IDENTIFICATION
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* $PostgreSQL: pgsql/src/backend/storage/freespace/freespace.c,v 1.75 2010/02/09 00:28:57 tgl Exp $
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* $PostgreSQL: pgsql/src/backend/storage/freespace/freespace.c,v 1.76 2010/02/09 21:43:30 tgl Exp $
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*
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*
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* NOTES:
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@@ -25,16 +25,16 @@
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#include "access/htup.h"
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#include "access/xlogutils.h"
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#include "storage/bufpage.h"
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#include "miscadmin.h"
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#include "storage/bufmgr.h"
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#include "storage/bufpage.h"
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#include "storage/freespace.h"
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#include "storage/fsm_internals.h"
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#include "storage/lmgr.h"
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#include "storage/lwlock.h"
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#include "storage/smgr.h"
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#include "utils/rel.h"
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#include "utils/inval.h"
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#include "miscadmin.h"
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/*
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* We use just one byte to store the amount of free space on a page, so we
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@@ -251,9 +251,9 @@ GetRecordedFreeSpace(Relation rel, BlockNumber heapBlk)
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/*
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* FreeSpaceMapTruncateRel - adjust for truncation of a relation.
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*
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* The caller must hold AccessExclusiveLock on the relation, to ensure
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* that other backends receive the relcache invalidation event that this
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* function sends, before accessing the FSM again.
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* The caller must hold AccessExclusiveLock on the relation, to ensure that
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* other backends receive the smgr invalidation event that this function sends
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* before they access the FSM again.
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*
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* nblocks is the new size of the heap.
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*/
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@@ -302,17 +302,18 @@ FreeSpaceMapTruncateRel(Relation rel, BlockNumber nblocks)
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return; /* nothing to do; the FSM was already smaller */
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}
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/* Truncate the unused FSM pages */
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/* Truncate the unused FSM pages, and send smgr inval message */
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smgrtruncate(rel->rd_smgr, FSM_FORKNUM, new_nfsmblocks, rel->rd_istemp);
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/*
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* Need to invalidate the relcache entry, because rd_fsm_nblocks seen by
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* other backends is no longer valid.
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* We might as well update the local smgr_fsm_nblocks setting.
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* smgrtruncate sent an smgr cache inval message, which will cause
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* other backends to invalidate their copy of smgr_fsm_nblocks, and
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* this one too at the next command boundary. But this ensures it
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* isn't outright wrong until then.
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*/
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if (!InRecovery)
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CacheInvalidateRelcache(rel);
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rel->rd_fsm_nblocks = new_nfsmblocks;
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if (rel->rd_smgr)
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rel->rd_smgr->smgr_fsm_nblocks = new_nfsmblocks;
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}
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/*
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@@ -506,17 +507,24 @@ fsm_readbuf(Relation rel, FSMAddress addr, bool extend)
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RelationOpenSmgr(rel);
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/* If we haven't cached the size of the FSM yet, check it first */
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if (rel->rd_fsm_nblocks == InvalidBlockNumber)
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/*
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* If we haven't cached the size of the FSM yet, check it first. Also
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* recheck if the requested block seems to be past end, since our
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* cached value might be stale. (We send smgr inval messages on
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* truncation, but not on extension.)
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*/
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if (rel->rd_smgr->smgr_fsm_nblocks == InvalidBlockNumber ||
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blkno >= rel->rd_smgr->smgr_fsm_nblocks)
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{
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if (smgrexists(rel->rd_smgr, FSM_FORKNUM))
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rel->rd_fsm_nblocks = smgrnblocks(rel->rd_smgr, FSM_FORKNUM);
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rel->rd_smgr->smgr_fsm_nblocks = smgrnblocks(rel->rd_smgr,
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FSM_FORKNUM);
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else
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rel->rd_fsm_nblocks = 0;
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rel->rd_smgr->smgr_fsm_nblocks = 0;
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}
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/* Handle requests beyond EOF */
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if (blkno >= rel->rd_fsm_nblocks)
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if (blkno >= rel->rd_smgr->smgr_fsm_nblocks)
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{
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if (extend)
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fsm_extend(rel, blkno + 1);
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@@ -559,19 +567,23 @@ fsm_extend(Relation rel, BlockNumber fsm_nblocks)
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* it.
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*
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* Note that another backend might have extended or created the relation
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* before we get the lock.
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* by the time we get the lock.
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*/
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LockRelationForExtension(rel, ExclusiveLock);
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/* Create the FSM file first if it doesn't exist */
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if ((rel->rd_fsm_nblocks == 0 || rel->rd_fsm_nblocks == InvalidBlockNumber)
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&& !smgrexists(rel->rd_smgr, FSM_FORKNUM))
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{
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/* Might have to re-open if a cache flush happened */
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RelationOpenSmgr(rel);
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/*
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* Create the FSM file first if it doesn't exist. If smgr_fsm_nblocks
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* is positive then it must exist, no need for an smgrexists call.
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*/
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if ((rel->rd_smgr->smgr_fsm_nblocks == 0 ||
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rel->rd_smgr->smgr_fsm_nblocks == InvalidBlockNumber) &&
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!smgrexists(rel->rd_smgr, FSM_FORKNUM))
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smgrcreate(rel->rd_smgr, FSM_FORKNUM, false);
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fsm_nblocks_now = 0;
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}
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else
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fsm_nblocks_now = smgrnblocks(rel->rd_smgr, FSM_FORKNUM);
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fsm_nblocks_now = smgrnblocks(rel->rd_smgr, FSM_FORKNUM);
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while (fsm_nblocks_now < fsm_nblocks)
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{
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@@ -580,14 +592,12 @@ fsm_extend(Relation rel, BlockNumber fsm_nblocks)
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fsm_nblocks_now++;
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}
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/* Update local cache with the up-to-date size */
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rel->rd_smgr->smgr_fsm_nblocks = fsm_nblocks_now;
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UnlockRelationForExtension(rel, ExclusiveLock);
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pfree(pg);
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/* Update the relcache with the up-to-date size */
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if (!InRecovery)
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CacheInvalidateRelcache(rel);
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rel->rd_fsm_nblocks = fsm_nblocks_now;
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}
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/*
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