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Fix up rickety handling of relation-truncation interlocks.

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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visibilitymap.c about when rd_fsm_nblocks and rd_vm_nblocks can be out of
date.
This commit is contained in:
Tom Lane
2010-02-09 21:43:30 +00:00
parent 79647eed86
commit cbe9d6beb4
15 changed files with 210 additions and 219 deletions
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10
src/backend/commands/vacuum.c
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@@ -14,7 +14,7 @@
*
*
* IDENTIFICATION
* $PostgreSQL: pgsql/src/backend/commands/vacuum.c,v 1.406 2010/02/08 16:50:21 tgl Exp $
* $PostgreSQL: pgsql/src/backend/commands/vacuum.c,v 1.407 2010/02/09 21:43:30 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@@ -789,7 +789,6 @@ vacuum_rel(Oid relid, VacuumStmt *vacstmt, bool do_toast, bool for_wraparound,
Oid save_userid;
int save_sec_context;
int save_nestlevel;
bool heldoff;
if (scanned_all)
*scanned_all = false;
@@ -970,10 +969,9 @@ vacuum_rel(Oid relid, VacuumStmt *vacstmt, bool do_toast, bool for_wraparound,
cluster_rel(relid, InvalidOid, false,
(vacstmt->options & VACOPT_VERBOSE) != 0,
vacstmt->freeze_min_age, vacstmt->freeze_table_age);
heldoff = false;
}
else
heldoff = lazy_vacuum_rel(onerel, vacstmt, vac_strategy, scanned_all);
lazy_vacuum_rel(onerel, vacstmt, vac_strategy, scanned_all);
/* Roll back any GUC changes executed by index functions */
AtEOXact_GUC(false, save_nestlevel);
@@ -991,10 +989,6 @@ vacuum_rel(Oid relid, VacuumStmt *vacstmt, bool do_toast, bool for_wraparound,
PopActiveSnapshot();
CommitTransactionCommand();
/* now we can allow interrupts again, if disabled */
if (heldoff)
RESUME_INTERRUPTS();
/*
* If the relation has a secondary toast rel, vacuum that too while we
* still hold the session lock on the master table. Note however that