From: Tom Lane <tgl@sss.pgh.pa.us>
Date: Wed, 8 Jan 2003 22:06:23 +0000 (+0000)
Subject: Reconsider old decision to try to constant-fold default and constraint
X-Git-Tag: REL7_4_BETA1~1262
X-Git-Url: https://granicus.if.org/sourcecode?a=commitdiff_plain;h=2d140d35a4170a6ad20dae5c01a381b5b4a4b6a3;p=postgresql

Reconsider old decision to try to constant-fold default and constraint
expressions before they are stored.  This seems like not such a hot idea,
particularly now that the constant-folder will try to inline SQL functions.
---

diff --git a/src/backend/catalog/heap.c b/src/backend/catalog/heap.c
index 3d671e92f3..8d176c12cd 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 1.238 2002/12/16 18:39:22 tgl Exp $
+ *	  $Header: /cvsroot/pgsql/src/backend/catalog/heap.c,v 1.239 2003/01/08 22:06:20 tgl Exp $
  *
  *
  * INTERFACE ROUTINES
@@ -1604,11 +1604,6 @@ AddRelationRawConstraints(Relation rel,
 		if (contain_agg_clause(expr))
 			elog(ERROR, "cannot use aggregate function in CHECK constraint expression");
 
-		/*
-		 * Might as well try to reduce any constant expressions.
-		 */
-		expr = eval_const_expressions(expr);
-
 		/*
 		 * Constraints are evaluated with execQual, which expects an
 		 * implicit-AND list, so convert expression to implicit-AND form.
@@ -1733,7 +1728,7 @@ cookDefault(ParseState *pstate,
 	 * column's type.  We store the expression without coercion, however,
 	 * to avoid premature coercion in cases like
 	 *
-	 * CREATE TABLE tbl (fld timestamp DEFAULT 'now'::text);
+	 * CREATE TABLE tbl (fld timestamp DEFAULT 'now');
 	 *
 	 * NB: this should match the code in rewrite/rewriteHandler.c that will
 	 * actually do the coercion, to ensure we don't accept an unusable
@@ -1755,11 +1750,6 @@ cookDefault(ParseState *pstate,
 				 format_type_be(type_id));
 	}
 
-	/*
-	 * Might as well try to reduce any constant expressions.
-	 */
-	expr = eval_const_expressions(expr);
-
 	return (expr);
 }
 
diff --git a/src/backend/commands/tablecmds.c b/src/backend/commands/tablecmds.c
index 3f9cad16ce..84ea31885d 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 1.64 2002/12/30 19:45:17 tgl Exp $
+ *	  $Header: /cvsroot/pgsql/src/backend/commands/tablecmds.c,v 1.65 2003/01/08 22:06:23 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -2756,7 +2756,10 @@ AlterTableAddCheckConstraint(Relation rel, Constraint *constr)
 		elog(ERROR, "cannot use aggregate function in CHECK constraint expression");
 
 	/*
-	 * Might as well try to reduce any constant expressions.
+	 * Might as well try to reduce any constant expressions, so as to
+	 * minimize overhead while testing the constraint at each row.
+	 *
+	 * Note that the stored form of the constraint will NOT be const-folded.
 	 */
 	expr = eval_const_expressions(expr);
 
diff --git a/src/backend/commands/typecmds.c b/src/backend/commands/typecmds.c
index 7d4ff1f0b6..379e4bb9b4 100644
--- a/src/backend/commands/typecmds.c
+++ b/src/backend/commands/typecmds.c
@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $Header: /cvsroot/pgsql/src/backend/commands/typecmds.c,v 1.28 2003/01/08 21:40:39 tgl Exp $
+ *	  $Header: /cvsroot/pgsql/src/backend/commands/typecmds.c,v 1.29 2003/01/08 22:06:23 tgl Exp $
  *
  * DESCRIPTION
  *	  The "DefineFoo" routines take the parse tree and pick out the
@@ -1623,11 +1623,6 @@ domainAddConstraint(Oid domainOid, Oid domainNamespace, Oid baseTypeOid,
 	if (contain_agg_clause(expr))
 		elog(ERROR, "cannot use aggregate function in CHECK constraint expression");
 
-	/*
-	 * Might as well try to reduce any constant expressions.
-	 */
-	expr = eval_const_expressions(expr);
-
 	/*
 	 * Convert to string form for storage.
 	 */