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Commita195e3c

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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 parent928408d commita195e3c

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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
@@ -3425,14 +3425,12 @@ ATRewriteTables(List **wqueue, LOCKMODE lockmode)
34253425
Relationrefrel;
34263426

34273427
if (rel==NULL)
3428+
{
34283429
/* Long since locked, no need for another */
34293430
rel=heap_open(tab->relid,NoLock);
3431+
}
34303432

3431-
/*
3432-
* We're adding a trigger to both tables, so the lock level
3433-
* here should sensibly reflect that.
3434-
*/
3435-
refrel=heap_open(con->refrelid,ShareRowExclusiveLock);
3433+
refrel=heap_open(con->refrelid,RowShareLock);
34363434

34373435
validateForeignKeyConstraint(fkconstraint->conname,rel,refrel,
34383436
con->refindid,
@@ -5529,7 +5527,14 @@ ATAddForeignKeyConstraint(AlteredTableInfo *tab, Relation rel,
55295527
OidindexOid;
55305528
OidconstrOid;
55315529

5532-
pkrel=heap_openrv(fkconstraint->pktable,lockmode);
5530+
/*
5531+
* Grab an exclusive lock on the pk table, so that someone doesn't delete
5532+
* rows out from under us. (Although a lesser lock would do for that
5533+
* purpose, we'll need exclusive lock anyway to add triggers to the pk
5534+
* table; trying to start with a lesser lock will just create a risk of
5535+
* deadlock.)
5536+
*/
5537+
pkrel=heap_openrv(fkconstraint->pktable,AccessExclusiveLock);
55335538

55345539
/*
55355540
* 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
@@ -144,14 +144,7 @@ CreateTrigger(CreateTrigStmt *stmt, const char *queryString,
144144
ObjectAddressmyself,
145145
referenced;
146146

147-
/*
148-
* ShareRowExclusiveLock is sufficient to prevent concurrent write
149-
* activity to the relation, and thus to lock out any operations that
150-
* might want to fire triggers on the relation. If we had ON SELECT
151-
* triggers we would need to take an AccessExclusiveLock to add one of
152-
* those, just as we do with ON SELECT rules.
153-
*/
154-
rel=heap_openrv(stmt->relation,ShareRowExclusiveLock);
147+
rel=heap_openrv(stmt->relation,AccessExclusiveLock);
155148

156149
/*
157150
* Triggers must be on tables or views, and there are additional
@@ -481,7 +474,7 @@ CreateTrigger(CreateTrigStmt *stmt, const char *queryString,
481474
* can skip this for internally generated triggers, since the name
482475
* modification above should be sufficient.
483476
*
484-
* NOTE that this is cool only because we haveShareRowExclusiveLock on
477+
* NOTE that this is cool only because we haveAccessExclusiveLock on
485478
* the relation, so the trigger set won't be changing underneath us.
486479
*/
487480
if (!isInternal)
@@ -1085,14 +1078,11 @@ RemoveTriggerById(Oid trigOid)
10851078
elog(ERROR,"could not find tuple for trigger %u",trigOid);
10861079

10871080
/*
1088-
* Open and lock the relation the trigger belongs to. As in
1089-
* CreateTrigger, this is sufficient to lock out all operations that could
1090-
* fire or add triggers; but it would need to be revisited if we had ON
1091-
* SELECT triggers.
1081+
* Open and exclusive-lock the relation the trigger belongs to.
10921082
*/
10931083
relid= ((Form_pg_trigger)GETSTRUCT(tup))->tgrelid;
10941084

1095-
rel=heap_open(relid,ShareRowExclusiveLock);
1085+
rel=heap_open(relid,AccessExclusiveLock);
10961086

10971087
if (rel->rd_rel->relkind!=RELKIND_RELATION&&
10981088
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
@@ -238,14 +238,12 @@ DefineQueryRewrite(char *rulename,
238238
/*
239239
* If we are installing an ON SELECT rule, we had better grab
240240
* AccessExclusiveLock to ensure no SELECTs are currently running on the
241-
* event relation.For other types of rules, it is sufficient to grab
242-
* ShareRowExclusiveLock to lock out insert/update/delete actions and to
243-
* ensure that we lock out current CREATE RULE statements.
241+
* event relation. For other types of rules, it would be sufficient to
242+
* grab ShareRowExclusiveLock to lock out insert/update/delete actions and
243+
* to ensure that we lock out current CREATE RULE statements; but because
244+
* of race conditions in access to catalog entries, we can't do that yet.
244245
*/
245-
if (event_type==CMD_SELECT)
246-
event_relation=heap_open(event_relid,AccessExclusiveLock);
247-
else
248-
event_relation=heap_open(event_relid,ShareRowExclusiveLock);
246+
event_relation=heap_open(event_relid,AccessExclusiveLock);
249247

250248
/*
251249
* Verify relation is of a type that rules can sensibly be applied to.

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