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Commitec1339e

Browse files
committed
Finish disabling reduced-lock-levels-for-DDL feature.
Previous patch only covered the ALTER TABLE changes, not changes in othercommands; and it neglected to revert the documentation changes.
1 parent046d52f commitec1339e

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4 files changed

+24
-32
lines changed

4 files changed

+24
-32
lines changed

‎doc/src/sgml/mvcc.sgml

Lines changed: 4 additions & 5 deletions
Original file line numberDiff line numberDiff line change
@@ -878,9 +878,8 @@ ERROR: could not serialize access due to read/write dependencies among transact
878878
</para>
879879

880880
<para>
881-
Acquired by <command>CREATE TRIGGER</command>,
882-
<command>CREATE RULE</command> (except for <literal>ON SELECT</>
883-
rules) and some forms of <command>ALTER TABLE</command>.
881+
This lock mode is not automatically acquired by any
882+
<productname>PostgreSQL</productname> command.
884883
</para>
885884
</listitem>
886885
</varlistentry>
@@ -925,10 +924,10 @@ ERROR: could not serialize access due to read/write dependencies among transact
925924
</para>
926925

927926
<para>
928-
Acquired by the <command>DROP TABLE</command>,
927+
Acquired by the <command>ALTER TABLE</>, <command>DROP TABLE</>,
929928
<command>TRUNCATE</command>, <command>REINDEX</command>,
930929
<command>CLUSTER</command>, and <command>VACUUM FULL</command>
931-
commands, and some forms of <command>ALTER TABLE</>.
930+
commands.
932931
This is also the default lock mode for <command>LOCK TABLE</command>
933932
statements that do not specify a mode explicitly.
934933
</para>

‎src/backend/commands/tablecmds.c

Lines changed: 11 additions & 6 deletions
Original file line numberDiff line numberDiff line change
@@ -3409,14 +3409,12 @@ ATRewriteTables(List **wqueue, LOCKMODE lockmode)
34093409
Relationrefrel;
34103410

34113411
if (rel==NULL)
3412+
{
34123413
/* Long since locked, no need for another */
34133414
rel=heap_open(tab->relid,NoLock);
3415+
}
34143416

3415-
/*
3416-
* We're adding a trigger to both tables, so the lock level
3417-
* here should sensibly reflect that.
3418-
*/
3419-
refrel=heap_open(con->refrelid,ShareRowExclusiveLock);
3417+
refrel=heap_open(con->refrelid,RowShareLock);
34203418

34213419
validateForeignKeyConstraint(fkconstraint->conname,rel,refrel,
34223420
con->refindid,
@@ -5508,7 +5506,14 @@ ATAddForeignKeyConstraint(AlteredTableInfo *tab, Relation rel,
55085506
OidindexOid;
55095507
OidconstrOid;
55105508

5511-
pkrel=heap_openrv(fkconstraint->pktable,lockmode);
5509+
/*
5510+
* Grab an exclusive lock on the pk table, so that someone doesn't delete
5511+
* rows out from under us. (Although a lesser lock would do for that
5512+
* purpose, we'll need exclusive lock anyway to add triggers to the pk
5513+
* table; trying to start with a lesser lock will just create a risk of
5514+
* deadlock.)
5515+
*/
5516+
pkrel=heap_openrv(fkconstraint->pktable,AccessExclusiveLock);
55125517

55135518
/*
55145519
* Validity checks (permission checks wait till we have the column

‎src/backend/commands/trigger.c

Lines changed: 4 additions & 14 deletions
Original file line numberDiff line numberDiff line change
@@ -143,14 +143,7 @@ CreateTrigger(CreateTrigStmt *stmt, const char *queryString,
143143
ObjectAddressmyself,
144144
referenced;
145145

146-
/*
147-
* ShareRowExclusiveLock is sufficient to prevent concurrent write
148-
* activity to the relation, and thus to lock out any operations that
149-
* might want to fire triggers on the relation. If we had ON SELECT
150-
* triggers we would need to take an AccessExclusiveLock to add one of
151-
* those, just as we do with ON SELECT rules.
152-
*/
153-
rel=heap_openrv(stmt->relation,ShareRowExclusiveLock);
146+
rel=heap_openrv(stmt->relation,AccessExclusiveLock);
154147

155148
/*
156149
* Triggers must be on tables or views, and there are additional
@@ -480,7 +473,7 @@ CreateTrigger(CreateTrigStmt *stmt, const char *queryString,
480473
* can skip this for internally generated triggers, since the name
481474
* modification above should be sufficient.
482475
*
483-
* NOTE that this is cool only because we haveShareRowExclusiveLock on
476+
* NOTE that this is cool only because we haveAccessExclusiveLock on
484477
* the relation, so the trigger set won't be changing underneath us.
485478
*/
486479
if (!isInternal)
@@ -1084,14 +1077,11 @@ RemoveTriggerById(Oid trigOid)
10841077
elog(ERROR,"could not find tuple for trigger %u",trigOid);
10851078

10861079
/*
1087-
* Open and lock the relation the trigger belongs to. As in
1088-
* CreateTrigger, this is sufficient to lock out all operations that could
1089-
* fire or add triggers; but it would need to be revisited if we had ON
1090-
* SELECT triggers.
1080+
* Open and exclusive-lock the relation the trigger belongs to.
10911081
*/
10921082
relid= ((Form_pg_trigger)GETSTRUCT(tup))->tgrelid;
10931083

1094-
rel=heap_open(relid,ShareRowExclusiveLock);
1084+
rel=heap_open(relid,AccessExclusiveLock);
10951085

10961086
if (rel->rd_rel->relkind!=RELKIND_RELATION&&
10971087
rel->rd_rel->relkind!=RELKIND_VIEW)

‎src/backend/rewrite/rewriteDefine.c

Lines changed: 5 additions & 7 deletions
Original file line numberDiff line numberDiff line change
@@ -240,14 +240,12 @@ DefineQueryRewrite(char *rulename,
240240
/*
241241
* If we are installing an ON SELECT rule, we had better grab
242242
* AccessExclusiveLock to ensure no SELECTs are currently running on the
243-
* event relation.For other types of rules, it is sufficient to grab
244-
* ShareRowExclusiveLock to lock out insert/update/delete actions and to
245-
* ensure that we lock out current CREATE RULE statements.
243+
* event relation. For other types of rules, it would be sufficient to
244+
* grab ShareRowExclusiveLock to lock out insert/update/delete actions and
245+
* to ensure that we lock out current CREATE RULE statements; but because
246+
* of race conditions in access to catalog entries, we can't do that yet.
246247
*/
247-
if (event_type==CMD_SELECT)
248-
event_relation=heap_open(event_relid,AccessExclusiveLock);
249-
else
250-
event_relation=heap_open(event_relid,ShareRowExclusiveLock);
248+
event_relation=heap_open(event_relid,AccessExclusiveLock);
251249

252250
/*
253251
* Verify relation is of a type that rules can sensibly be applied to.

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