diff --git a/doc/src/sgml/ref/truncate.sgml b/doc/src/sgml/ref/truncate.sgml
index fc65f65db55ed98df99eb53f5fbb1ee4a9e10ca1..aa27890f47eb6f40ae2b7bd5ba0cb889d0a7fe64 100644
--- a/doc/src/sgml/ref/truncate.sgml
+++ b/doc/src/sgml/ref/truncate.sgml
@@ -1,5 +1,5 @@
<!--
-$Header: /cvsroot/pgsql/doc/src/sgml/ref/truncate.sgml,v 1.13 2003/09/12 00:12:47 tgl Exp $
+$Header: /cvsroot/pgsql/doc/src/sgml/ref/truncate.sgml,v 1.14 2003/09/19 21:04:19 tgl Exp $
PostgreSQL documentation
-->
@@ -50,6 +50,16 @@ TRUNCATE [ TABLE ] <replaceable class="PARAMETER">name</replaceable>
</variablelist>
</refsect1>
+ <refsect1>
+ <title>Notes</title>
+
+ <para>
+ <command>TRUNCATE</> cannot be used if there are foreign-key references
+ to the table from other tables. Checking validity in such cases would
+ require table scans, and the whole point is not to do one.
+ </para>
+ </refsect1>
+
<refsect1>
<title>Examples</title>
diff --git a/src/backend/catalog/heap.c b/src/backend/catalog/heap.c
index c3253677f9382f53acfa594cecadb2cf6fc71839..ce189ff903bb1471afc3febed74dd82922d1ddbb 100644
--- a/src/backend/catalog/heap.c
+++ b/src/backend/catalog/heap.c
@@ -8,7 +8,7 @@
*
*
* IDENTIFICATION
- * $Header: /cvsroot/pgsql/src/backend/catalog/heap.c,v 1.251 2003/08/04 02:39:58 momjian Exp $
+ * $Header: /cvsroot/pgsql/src/backend/catalog/heap.c,v 1.252 2003/09/19 21:04:19 tgl Exp $
*
*
* INTERFACE ROUTINES
@@ -1966,9 +1966,11 @@ RelationTruncateIndexes(Oid heapId)
/*
* heap_truncate
*
- * This routine is used to truncate the data from the
- * storage manager of any data within the relation handed
- * to this routine. This is not transaction-safe!
+ * This routine deletes all data within the specified relation.
+ *
+ * This is not transaction-safe! There is another, transaction-safe
+ * implementation in commands/cluster.c. We now use this only for
+ * ON COMMIT truncation of temporary tables, where it doesn't matter.
*/
void
heap_truncate(Oid rid)
@@ -1979,6 +1981,9 @@ heap_truncate(Oid rid)
/* Open relation for processing, and grab exclusive access on it. */
rel = heap_open(rid, AccessExclusiveLock);
+ /* Don't allow truncate on tables that are referenced by foreign keys */
+ heap_truncate_check_FKs(rel);
+
/*
* Release any buffers associated with this relation. If they're
* dirty, they're just dropped without bothering to flush to disk.
@@ -2003,3 +2008,61 @@ heap_truncate(Oid rid)
*/
heap_close(rel, NoLock);
}
+
+/*
+ * heap_truncate_check_FKs
+ * Check for foreign keys referencing a relation that's to be truncated
+ *
+ * We disallow such FKs (except self-referential ones) since the whole point
+ * of TRUNCATE is to not scan the individual rows to be thrown away.
+ *
+ * This is split out so it can be shared by both implementations of truncate.
+ * Caller should already hold a suitable lock on the relation.
+ */
+void
+heap_truncate_check_FKs(Relation rel)
+{
+ Oid relid = RelationGetRelid(rel);
+ ScanKeyData key;
+ Relation fkeyRel;
+ SysScanDesc fkeyScan;
+ HeapTuple tuple;
+
+ /*
+ * Fast path: if the relation has no triggers, it surely has no FKs
+ * either.
+ */
+ if (rel->rd_rel->reltriggers == 0)
+ return;
+
+ /*
+ * Otherwise, must scan pg_constraint. Right now, this is a seqscan
+ * because there is no available index on confrelid.
+ */
+ fkeyRel = heap_openr(ConstraintRelationName, AccessShareLock);
+
+ ScanKeyEntryInitialize(&key, 0,
+ Anum_pg_constraint_confrelid,
+ F_OIDEQ,
+ ObjectIdGetDatum(relid));
+
+ fkeyScan = systable_beginscan(fkeyRel, NULL, false,
+ SnapshotNow, 1, &key);
+
+ while (HeapTupleIsValid(tuple = systable_getnext(fkeyScan)))
+ {
+ Form_pg_constraint con = (Form_pg_constraint) GETSTRUCT(tuple);
+
+ if (con->contype == CONSTRAINT_FOREIGN && con->conrelid != relid)
+ ereport(ERROR,
+ (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
+ errmsg("cannot truncate a table referenced in a foreign key constraint"),
+ errdetail("Table \"%s\" references \"%s\" via foreign key constraint \"%s\".",
+ get_rel_name(con->conrelid),
+ RelationGetRelationName(rel),
+ NameStr(con->conname))));
+ }
+
+ systable_endscan(fkeyScan);
+ heap_close(fkeyRel, AccessShareLock);
+}
diff --git a/src/backend/commands/tablecmds.c b/src/backend/commands/tablecmds.c
index b99d68b3400695d304f3983f06d5acc700c81453..fc8a87123fe15aafed0c1625822de91f83529265 100644
--- a/src/backend/commands/tablecmds.c
+++ b/src/backend/commands/tablecmds.c
@@ -8,7 +8,7 @@
*
*
* IDENTIFICATION
- * $Header: /cvsroot/pgsql/src/backend/commands/tablecmds.c,v 1.81 2003/09/15 00:26:31 petere Exp $
+ * $Header: /cvsroot/pgsql/src/backend/commands/tablecmds.c,v 1.82 2003/09/19 21:04:20 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@@ -365,15 +365,9 @@ void
TruncateRelation(const RangeVar *relation)
{
Relation rel;
- Oid relid;
- ScanKeyData key;
- Relation fkeyRel;
- SysScanDesc fkeyScan;
- HeapTuple tuple;
/* Grab exclusive lock in preparation for truncate */
rel = heap_openrv(relation, AccessExclusiveLock);
- relid = RelationGetRelid(rel);
/* Only allow truncate on regular tables */
if (rel->rd_rel->relkind != RELKIND_RELATION)
@@ -383,7 +377,7 @@ TruncateRelation(const RangeVar *relation)
RelationGetRelationName(rel))));
/* Permissions checks */
- if (!pg_class_ownercheck(relid, GetUserId()))
+ if (!pg_class_ownercheck(RelationGetRelid(rel), GetUserId()))
aclcheck_error(ACLCHECK_NOT_OWNER, ACL_KIND_CLASS,
RelationGetRelationName(rel));
@@ -405,35 +399,7 @@ TruncateRelation(const RangeVar *relation)
/*
* Don't allow truncate on tables which are referenced by foreign keys
*/
- fkeyRel = heap_openr(ConstraintRelationName, AccessShareLock);
-
- ScanKeyEntryInitialize(&key, 0,
- Anum_pg_constraint_confrelid,
- F_OIDEQ,
- ObjectIdGetDatum(relid));
-
- fkeyScan = systable_beginscan(fkeyRel, 0, false,
- SnapshotNow, 1, &key);
-
- /*
- * First foreign key found with us as the reference should throw an
- * error.
- */
- while (HeapTupleIsValid(tuple = systable_getnext(fkeyScan)))
- {
- Form_pg_constraint con = (Form_pg_constraint) GETSTRUCT(tuple);
-
- if (con->contype == 'f' && con->conrelid != relid)
- ereport(ERROR,
- (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
- errmsg("cannot truncate a table referenced in a foreign key constraint"),
- errdetail("Table \"%s\" references this one via foreign key constraint \"%s\".",
- get_rel_name(con->conrelid),
- NameStr(con->conname))));
- }
-
- systable_endscan(fkeyScan);
- heap_close(fkeyRel, AccessShareLock);
+ heap_truncate_check_FKs(rel);
/*
* Do the real work using the same technique as cluster, but without
@@ -3137,11 +3103,28 @@ AlterTableAddForeignKeyConstraint(Relation rel, FkConstraint *fkconstraint)
aclcheck_error(aclresult, ACL_KIND_CLASS,
RelationGetRelationName(rel));
- if (isTempNamespace(RelationGetNamespace(pkrel)) &&
- !isTempNamespace(RelationGetNamespace(rel)))
- ereport(ERROR,
- (errcode(ERRCODE_INVALID_TABLE_DEFINITION),
- errmsg("cannot reference temporary table from permanent table constraint")));
+ /*
+ * Disallow reference from permanent table to temp table or vice versa.
+ * (The ban on perm->temp is for fairly obvious reasons. The ban on
+ * temp->perm is because other backends might need to run the RI triggers
+ * on the perm table, but they can't reliably see tuples the owning
+ * backend has created in the temp table, because non-shared buffers
+ * are used for temp tables.)
+ */
+ if (isTempNamespace(RelationGetNamespace(pkrel)))
+ {
+ if (!isTempNamespace(RelationGetNamespace(rel)))
+ ereport(ERROR,
+ (errcode(ERRCODE_INVALID_TABLE_DEFINITION),
+ errmsg("cannot reference temporary table from permanent table constraint")));
+ }
+ else
+ {
+ if (isTempNamespace(RelationGetNamespace(rel)))
+ ereport(ERROR,
+ (errcode(ERRCODE_INVALID_TABLE_DEFINITION),
+ errmsg("cannot reference permanent table from temporary table constraint")));
+ }
/*
* Look up the referencing attributes to make sure they exist, and
diff --git a/src/include/catalog/heap.h b/src/include/catalog/heap.h
index 86c97ff4786179b119db2701a4c20deb0cf84b90..a9cd65ff06812b35471a7fa9b6728d00865c64ee 100644
--- a/src/include/catalog/heap.h
+++ b/src/include/catalog/heap.h
@@ -7,7 +7,7 @@
* Portions Copyright (c) 1996-2003, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
- * $Id: heap.h,v 1.61 2003/08/04 02:40:10 momjian Exp $
+ * $Id: heap.h,v 1.62 2003/09/19 21:04:20 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@@ -48,6 +48,8 @@ extern void heap_drop_with_catalog(Oid rid);
extern void heap_truncate(Oid rid);
+extern void heap_truncate_check_FKs(Relation rel);
+
extern void AddRelationRawConstraints(Relation rel,
List *rawColDefaults,
List *rawConstraints);
diff --git a/src/test/regress/expected/truncate.out b/src/test/regress/expected/truncate.out
index 91ea40b7929cca531e412c0c2bf5f31aff1caad4..2cd41f83ba063613592f05e665c82e1293143e50 100644
--- a/src/test/regress/expected/truncate.out
+++ b/src/test/regress/expected/truncate.out
@@ -42,7 +42,7 @@ SELECT * FROM truncate_a;
TRUNCATE truncate_a;
ERROR: cannot truncate a table referenced in a foreign key constraint
-DETAIL: Table "truncate_b" references this one via foreign key constraint "$1".
+DETAIL: Table "truncate_b" references "truncate_a" via foreign key constraint "$1".
SELECT * FROM truncate_a;
col1
------