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ALTER TABLE ... ALTER CONSTRAINT for FKs 

Allow constraint attributes to be altered,
so the default setting of NOT DEFERRABLE
can be altered to DEFERRABLE and back.

Review by Abhijit Menon-Sen
This commit is contained in:
Simon Riggs 2013-06-29 00:27:30 +01:00
parent 2f74e4ec50
commit f177cbfe67
6 changed files with 205 additions and 0 deletions
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11
doc/src/sgml/ref/alter_table.sgml
View File

@ -46,6 +46,7 @@ ALTER TABLE [ IF EXISTS ] <replaceable class="PARAMETER">name</replaceable>
ALTER [ COLUMN ] <replaceable class="PARAMETER">column_name</replaceable> SET STORAGE { PLAIN | EXTERNAL | EXTENDED | MAIN }
ADD <replaceable class="PARAMETER">table_constraint</replaceable> [ NOT VALID ]
ADD <replaceable class="PARAMETER">table_constraint_using_index</replaceable>
ALTER CONSTRAINT <replaceable class="PARAMETER">constraint_name</replaceable> [ DEFERRABLE | NOT DEFERRABLE ] [ INITIALLY DEFERRED | INITIALLY IMMEDIATE ]
VALIDATE CONSTRAINT <replaceable class="PARAMETER">constraint_name</replaceable>
DROP CONSTRAINT [ IF EXISTS ] <replaceable class="PARAMETER">constraint_name</replaceable> [ RESTRICT | CASCADE ]
DISABLE TRIGGER [ <replaceable class="PARAMETER">trigger_name</replaceable> | ALL | USER ]
@ -316,6 +317,16 @@ ALTER TABLE [ IF EXISTS ] <replaceable class="PARAMETER">name</replaceable>
</listitem>
</varlistentry>
<varlistentry>
<term><literal>ALTER CONSTRAINT</literal></term>
<listitem>
<para>
This form alters the attributes of a constraint that was previously
created. Currently only foreign key constraints may be altered.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><literal>VALIDATE CONSTRAINT</literal></term>
<listitem>

139
src/backend/commands/tablecmds.c
View File

@ -276,6 +276,8 @@ static void AlterIndexNamespaces(Relation classRel, Relation rel,
static void AlterSeqNamespaces(Relation classRel, Relation rel,
Oid oldNspOid, Oid newNspOid, ObjectAddresses *objsMoved,
LOCKMODE lockmode);
static void ATExecAlterConstraint(Relation rel, AlterTableCmd *cmd,
bool recurse, bool recursing, LOCKMODE lockmode);
static void ATExecValidateConstraint(Relation rel, char *constrName,
bool recurse, bool recursing, LOCKMODE lockmode);
static int transformColumnNameList(Oid relId, List *colList,
@ -2887,6 +2889,7 @@ AlterTableGetLockLevel(List *cmds)
case AT_SetOptions:
case AT_ResetOptions:
case AT_SetStorage:
case AT_AlterConstraint:
case AT_ValidateConstraint:
cmd_lockmode = ShareUpdateExclusiveLock;
break;
@ -3125,6 +3128,10 @@ ATPrepCmd(List **wqueue, Relation rel, AlterTableCmd *cmd,
ATPrepAddInherit(rel);
pass = AT_PASS_MISC;
break;
case AT_AlterConstraint: /* ALTER CONSTRAINT */
ATSimplePermissions(rel, ATT_TABLE);
pass = AT_PASS_MISC;
break;
case AT_ValidateConstraint: /* VALIDATE CONSTRAINT */
ATSimplePermissions(rel, ATT_TABLE);
/* Recursion occurs during execution phase */
@ -3304,6 +3311,9 @@ ATExecCmd(List **wqueue, AlteredTableInfo *tab, Relation rel,
case AT_AddIndexConstraint: /* ADD CONSTRAINT USING INDEX */
ATExecAddIndexConstraint(tab, rel, (IndexStmt *) cmd->def, lockmode);
break;
case AT_AlterConstraint: /* ALTER CONSTRAINT */
ATExecAlterConstraint(rel, cmd, false, false, lockmode);
break;
case AT_ValidateConstraint: /* VALIDATE CONSTRAINT */
ATExecValidateConstraint(rel, cmd->name, false, false, lockmode);
break;
@ -6175,6 +6185,135 @@ ATAddForeignKeyConstraint(AlteredTableInfo *tab, Relation rel,
heap_close(pkrel, NoLock);
}
/*
* ALTER TABLE ALTER CONSTRAINT
*
* Update the attributes of a constraint.
*
* Currently only works for Foreign Key constraints.
* Foreign keys do not inherit, so we purposely ignore the
* recursion bit here, but we keep the API the same for when
* other constraint types are supported.
*/
static void
ATExecAlterConstraint(Relation rel, AlterTableCmd *cmd,
bool recurse, bool recursing, LOCKMODE lockmode)
{
Relation conrel;
SysScanDesc scan;
ScanKeyData key;
HeapTuple contuple;
Form_pg_constraint currcon = NULL;
Constraint *cmdcon = NULL;
bool found = false;
Assert(IsA(cmd->def, Constraint));
cmdcon = (Constraint *) cmd->def;
conrel = heap_open(ConstraintRelationId, RowExclusiveLock);
/*
* Find and check the target constraint
*/
ScanKeyInit(&key,
Anum_pg_constraint_conrelid,
BTEqualStrategyNumber, F_OIDEQ,
ObjectIdGetDatum(RelationGetRelid(rel)));
scan = systable_beginscan(conrel, ConstraintRelidIndexId,
true, SnapshotNow, 1, &key);
while (HeapTupleIsValid(contuple = systable_getnext(scan)))
{
currcon = (Form_pg_constraint) GETSTRUCT(contuple);
if (strcmp(NameStr(currcon->conname), cmdcon->conname) == 0)
{
found = true;
break;
}
}
if (!found)
ereport(ERROR,
(errcode(ERRCODE_UNDEFINED_OBJECT),
errmsg("constraint \"%s\" of relation \"%s\" does not exist",
cmdcon->conname, RelationGetRelationName(rel))));
if (currcon->contype != CONSTRAINT_FOREIGN)
ereport(ERROR,
(errcode(ERRCODE_WRONG_OBJECT_TYPE),
errmsg("constraint \"%s\" of relation \"%s\" is not a foreign key constraint",
cmdcon->conname, RelationGetRelationName(rel))));
if (currcon->condeferrable != cmdcon->deferrable ||
currcon->condeferred != cmdcon->initdeferred)
{
HeapTuple copyTuple;
HeapTuple tgtuple;
Form_pg_constraint copy_con;
Form_pg_trigger copy_tg;
ScanKeyData tgkey;
SysScanDesc tgscan;
Relation tgrel;
/*
* Now update the catalog, while we have the door open.
*/
copyTuple = heap_copytuple(contuple);
copy_con = (Form_pg_constraint) GETSTRUCT(copyTuple);
copy_con->condeferrable = cmdcon->deferrable;
copy_con->condeferred = cmdcon->initdeferred;
simple_heap_update(conrel, &copyTuple->t_self, copyTuple);
CatalogUpdateIndexes(conrel, copyTuple);
InvokeObjectPostAlterHook(ConstraintRelationId,
HeapTupleGetOid(contuple), 0);
heap_freetuple(copyTuple);
/*
* Now we need to update the multiple entries in pg_trigger
* that implement the constraint.
*/
tgrel = heap_open(TriggerRelationId, RowExclusiveLock);
ScanKeyInit(&tgkey,
Anum_pg_trigger_tgconstraint,
BTEqualStrategyNumber, F_OIDEQ,
ObjectIdGetDatum(HeapTupleGetOid(contuple)));
tgscan = systable_beginscan(tgrel, TriggerConstraintIndexId, true,
SnapshotNow, 1, &tgkey);
while (HeapTupleIsValid(tgtuple = systable_getnext(tgscan)))
{
copyTuple = heap_copytuple(tgtuple);
copy_tg = (Form_pg_trigger) GETSTRUCT(copyTuple);
copy_tg->tgdeferrable = cmdcon->deferrable;
copy_tg->tginitdeferred = cmdcon->initdeferred;
simple_heap_update(tgrel, &copyTuple->t_self, copyTuple);
CatalogUpdateIndexes(tgrel, copyTuple);
InvokeObjectPostAlterHook(TriggerRelationId,
HeapTupleGetOid(tgtuple), 0);
heap_freetuple(copyTuple);
}
systable_endscan(tgscan);
heap_close(tgrel, RowExclusiveLock);
/*
* Invalidate relcache so that others see the new attributes.
*/
CacheInvalidateRelcache(rel);
}
systable_endscan(scan);
heap_close(conrel, RowExclusiveLock);
}
/*
* ALTER TABLE VALIDATE CONSTRAINT
*

15
src/backend/parser/gram.y
View File

@ -1943,6 +1943,21 @@ alter_table_cmd:
n->def = $2;
$$ = (Node *)n;
}
/* ALTER TABLE <name> ALTER CONSTRAINT ... */
| ALTER CONSTRAINT name ConstraintAttributeSpec
{
AlterTableCmd *n = makeNode(AlterTableCmd);
Constraint *c = makeNode(Constraint);
n->subtype = AT_AlterConstraint;
n->def = (Node *) c;
c->contype = CONSTR_FOREIGN; /* others not supported, yet */
c->conname = $3;
processCASbits($4, @4, "ALTER CONSTRAINT statement",
&c->deferrable,
&c->initdeferred,
NULL, NULL, yyscanner);
$$ = (Node *)n;
}
/* ALTER TABLE <name> VALIDATE CONSTRAINT ... */
| VALIDATE CONSTRAINT name
{

1
src/include/nodes/parsenodes.h
View File

@ -1209,6 +1209,7 @@ typedef enum AlterTableType
AT_AddConstraint, /* add constraint */
AT_AddConstraintRecurse, /* internal to commands/tablecmds.c */
AT_ReAddConstraint, /* internal to commands/tablecmds.c */
AT_AlterConstraint, /* alter constraint */
AT_ValidateConstraint, /* validate constraint */
AT_ValidateConstraintRecurse, /* internal to commands/tablecmds.c */
AT_ProcessedConstraint, /* pre-processed add constraint (local in

19
src/test/regress/expected/foreign_key.out
View File

@ -1132,6 +1132,15 @@ CREATE TEMP TABLE fktable (
id int primary key,
fk int references pktable deferrable initially deferred
);
-- check ALTER CONSTRAINT
ALTER TABLE fktable ALTER CONSTRAINT fktable_fk_fkey NOT DEFERRABLE;
-- illegal option
ALTER TABLE fktable ALTER CONSTRAINT fktable_fk_fkey NOT DEFERRABLE INITIALLY DEFERRED;
ERROR: constraint declared INITIALLY DEFERRED must be DEFERRABLE
LINE 1: ...e ALTER CONSTRAINT fktable_fk_fkey NOT DEFERRABLE INITIALLY ...
^
-- reset
ALTER TABLE fktable ALTER CONSTRAINT fktable_fk_fkey DEFERRABLE INITIALLY DEFERRED;
INSERT INTO pktable VALUES (5, 10);
BEGIN;
-- doesn't match PK, but no error yet
@ -1142,6 +1151,16 @@ UPDATE fktable SET id = id + 1;
COMMIT;
ERROR: insert or update on table "fktable" violates foreign key constraint "fktable_fk_fkey"
DETAIL: Key (fk)=(20) is not present in table "pktable".
-- change the constraint definition and retest
ALTER TABLE fktable ALTER CONSTRAINT fktable_fk_fkey DEFERRABLE INITIALLY IMMEDIATE;
BEGIN;
-- doesn't match PK, should throw error now
INSERT INTO fktable VALUES (0, 20);
ERROR: insert or update on table "fktable" violates foreign key constraint "fktable_fk_fkey"
DETAIL: Key (fk)=(20) is not present in table "pktable".
COMMIT;
-- reset
ALTER TABLE fktable ALTER CONSTRAINT fktable_fk_fkey DEFERRABLE INITIALLY DEFERRED;
-- check same case when insert is in a different subtransaction than update
BEGIN;
-- doesn't match PK, but no error yet

20
src/test/regress/sql/foreign_key.sql
View File

@ -818,6 +818,13 @@ CREATE TEMP TABLE fktable (
fk int references pktable deferrable initially deferred
);
-- check ALTER CONSTRAINT
ALTER TABLE fktable ALTER CONSTRAINT fktable_fk_fkey NOT DEFERRABLE;
-- illegal option
ALTER TABLE fktable ALTER CONSTRAINT fktable_fk_fkey NOT DEFERRABLE INITIALLY DEFERRED;
-- reset
ALTER TABLE fktable ALTER CONSTRAINT fktable_fk_fkey DEFERRABLE INITIALLY DEFERRED;
INSERT INTO pktable VALUES (5, 10);
BEGIN;
@ -831,6 +838,19 @@ UPDATE fktable SET id = id + 1;
-- should catch error from initial INSERT
COMMIT;
-- change the constraint definition and retest
ALTER TABLE fktable ALTER CONSTRAINT fktable_fk_fkey DEFERRABLE INITIALLY IMMEDIATE;
BEGIN;
-- doesn't match PK, should throw error now
INSERT INTO fktable VALUES (0, 20);
COMMIT;
-- reset
ALTER TABLE fktable ALTER CONSTRAINT fktable_fk_fkey DEFERRABLE INITIALLY DEFERRED;
-- check same case when insert is in a different subtransaction than update
BEGIN;