# Disallow TRUNCATE on tables that are involved in referential

constraints

The issue with finding and removing foreign key constraints is no longer
an issue, so please apply the attached.

It does NOT check for rules or on delete triggers (old style foreign
keys) as those are difficult to deal with (remove, truncate, re-add).

Rod Taylor

diff --git a/src/backend/commands/tablecmds.c b/src/backend/commands/tablecmds.c
index c6e8d686d41e61ea44e9b3ba82f02a08bc6913e3..1961ca1344ad90a73e90fb5ad2c918915611492a 100644 (file)
--- 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 1.30 2002/08/19 15:08:46 tgl Exp $
+ *   $Header: /cvsroot/pgsql/src/backend/commands/tablecmds.c,v 1.31 2002/08/22 04:51:05 momjian Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -332,6 +332,10 @@ 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);
@@ -356,6 +360,36 @@ TruncateRelation(const RangeVar *relation)
    if (!pg_class_ownercheck(relid, GetUserId()))
        aclcheck_error(ACLCHECK_NOT_OWNER, RelationGetRelationName(rel));
 
+   /*
+    * 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 foriegn 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')
+           elog(ERROR, "TRUNCATE cannot be used as other tables reference this one via foreign key constraint %s",
+                NameStr(con->conname));
+   }
+
+   systable_endscan(fkeyScan);
+   heap_close(fkeyRel, AccessShareLock);
+
    /* Keep the lock until transaction commit */
    heap_close(rel, NoLock);
 

diff --git a/src/test/regress/expected/truncate.out b/src/test/regress/expected/truncate.out
new file mode 100644 (file)
index 0000000..19300f6
--- /dev/null
+++ b/src/test/regress/expected/truncate.out
@@ -0,0 +1,38 @@
+-- Test basic TRUNCATE functionality.
+CREATE TABLE truncate_a (col1 integer primary key);
+NOTICE:  CREATE TABLE / PRIMARY KEY will create implicit index 'truncate_a_pkey' for table 'truncate_a'
+INSERT INTO truncate_a VALUES (1);
+INSERT INTO truncate_a VALUES (2);
+SELECT * FROM truncate_a;
+ col1 
+------
+    1
+    2
+(2 rows)
+
+TRUNCATE truncate_a;
+SELECT * FROM truncate_a;
+ col1 
+------
+(0 rows)
+
+-- Test foreign constraint check
+CREATE TABLE truncate_b(col1 integer references truncate_a);
+NOTICE:  CREATE TABLE will create implicit trigger(s) for FOREIGN KEY check(s)
+INSERT INTO truncate_a VALUES (1);
+SELECT * FROM truncate_a;
+ col1 
+------
+    1
+(1 row)
+
+TRUNCATE truncate_a;
+ERROR:  TRUNCATE cannot be used as other tables reference this one via foreign key constraint $1
+SELECT * FROM truncate_a;
+ col1 
+------
+    1
+(1 row)
+
+DROP TABLE truncate_b;
+DROP TABLE truncate_a;

diff --git a/src/test/regress/parallel_schedule b/src/test/regress/parallel_schedule
index 0ac26307063ca4a3404ba336079f1c7d6afe52bc..e82d9421679cfb5d1e7045702790853ea91d89e4 100644 (file)
--- a/src/test/regress/parallel_schedule
+++ b/src/test/regress/parallel_schedule
@@ -74,4 +74,4 @@ test: select_views alter_table portals_p2 rules foreign_key cluster
 # The sixth group of parallel test
 # ----------
 # "plpgsql" cannot run concurrently with "rules"
-test: limit plpgsql temp domain rangefuncs copy2 conversion without_oid
+test: limit plpgsql temp domain rangefuncs copy2 conversion without_oid truncate

diff --git a/src/test/regress/serial_schedule b/src/test/regress/serial_schedule
index d7a6deed2c98b8a920e818edbab155cf97c33280..553df2dfe7d6939ae97789eb4dc043e8f85ec5c7 100644 (file)
--- a/src/test/regress/serial_schedule
+++ b/src/test/regress/serial_schedule
@@ -1,4 +1,4 @@
-# $Header: /cvsroot/pgsql/src/test/regress/serial_schedule,v 1.15 2002/08/11 02:06:32 tgl Exp $
+# $Header: /cvsroot/pgsql/src/test/regress/serial_schedule,v 1.16 2002/08/22 04:51:06 momjian Exp $
 # This should probably be in an order similar to parallel_schedule.
 test: boolean
 test: char
@@ -88,3 +88,4 @@ test: domain
 test: rangefuncs
 test: without_oid
 test: conversion
+test: truncate

diff --git a/src/test/regress/sql/truncate.sql b/src/test/regress/sql/truncate.sql
new file mode 100644 (file)
index 0000000..5333113
--- /dev/null
+++ b/src/test/regress/sql/truncate.sql
@@ -0,0 +1,17 @@
+-- Test basic TRUNCATE functionality.
+CREATE TABLE truncate_a (col1 integer primary key);
+INSERT INTO truncate_a VALUES (1);
+INSERT INTO truncate_a VALUES (2);
+SELECT * FROM truncate_a;
+TRUNCATE truncate_a;
+SELECT * FROM truncate_a;
+
+-- Test foreign constraint check
+CREATE TABLE truncate_b(col1 integer references truncate_a);
+INSERT INTO truncate_a VALUES (1);
+SELECT * FROM truncate_a;
+TRUNCATE truncate_a;
+SELECT * FROM truncate_a;
+
+DROP TABLE truncate_b;
+DROP TABLE truncate_a;