Add an option to AlterTableCreateToastTable() to allow its caller to force

a toast table to be built, even if the sum-of-column-widths calculation
indicates one isn't needed.  This is needed by pg_migrator because if the
old table has a toast table, we have to migrate over the toast table since
it might contain some live data, even though subsequent column drops could
mean that no recently-added rows could require toasting.

Author: tglsfdc

src/backend/catalog/toasting.c

@@ -8,7 +8,7 @@
  * Portions Copyright (c) 1994, Regents of the University of California
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/catalog/toasting.c,v 1.14 2009/03/31 22:12:46 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/backend/catalog/toasting.c,v 1.15 2009/05/07 22:58:28 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -33,21 +33,25 @@
 
 
 static bool create_toast_table(Relation rel, Oid toastOid, Oid toastIndexOid,
-				   Datum reloptions);
+				   Datum reloptions, bool force);
 static bool needs_toast_table(Relation rel);
 
 
 /*
  * AlterTableCreateToastTable
  *		If the table needs a toast table, and doesn't already have one,
- *		then create a toast table for it.
+ *		then create a toast table for it.  (With the force option, make
+ *		a toast table even if it appears unnecessary.)
+ *
+ * reloptions for the toast table can be passed, too.  Pass (Datum) 0
+ * for default reloptions.
  *
  * We expect the caller to have verified that the relation is a table and have
  * already done any necessary permission checks.  Callers expect this function
  * to end with CommandCounterIncrement if it makes any changes.
  */
 void
-AlterTableCreateToastTable(Oid relOid, Datum reloptions)
+AlterTableCreateToastTable(Oid relOid, Datum reloptions, bool force)
 {
 	Relation	rel;
 
@@ -59,7 +63,7 @@ AlterTableCreateToastTable(Oid relOid, Datum reloptions)
 	rel = heap_open(relOid, AccessExclusiveLock);
 
 	/* create_toast_table does all the work */
-	(void) create_toast_table(rel, InvalidOid, InvalidOid, reloptions);
+	(void) create_toast_table(rel, InvalidOid, InvalidOid, reloptions, force);
 
 	heap_close(rel, NoLock);
 }
@@ -85,7 +89,7 @@ BootstrapToastTable(char *relName, Oid toastOid, Oid toastIndexOid)
 						relName)));
 
 	/* create_toast_table does all the work */
-	if (!create_toast_table(rel, toastOid, toastIndexOid, (Datum) 0))
+	if (!create_toast_table(rel, toastOid, toastIndexOid, (Datum) 0, false))
 		elog(ERROR, "\"%s\" does not require a toast table",
 			 relName);
 
@@ -101,7 +105,8 @@ BootstrapToastTable(char *relName, Oid toastOid, Oid toastIndexOid)
  * bootstrap they can be nonzero to specify hand-assigned OIDs
  */
 static bool
-create_toast_table(Relation rel, Oid toastOid, Oid toastIndexOid, Datum reloptions)
+create_toast_table(Relation rel, Oid toastOid, Oid toastIndexOid,
+				   Datum reloptions, bool force)
 {
 	Oid			relOid = RelationGetRelid(rel);
 	HeapTuple	reltup;
@@ -139,8 +144,12 @@ create_toast_table(Relation rel, Oid toastOid, Oid toastIndexOid, Datum reloptio
 
 	/*
 	 * Check to see whether the table actually needs a TOAST table.
+	 *
+	 * Caller can optionally override this check.  (Note: at present
+	 * no callers in core Postgres do so, but this option is needed by
+	 * pg_migrator.)
 	 */
-	if (!needs_toast_table(rel))
+	if (!force && !needs_toast_table(rel))
 		return false;
 
 	/*

src/backend/commands/cluster.c

@@ -11,7 +11,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/commands/cluster.c,v 1.183 2009/03/31 22:12:46 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/backend/commands/cluster.c,v 1.184 2009/05/07 22:58:28 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -741,7 +741,7 @@ make_new_heap(Oid OIDOldHeap, const char *NewName, Oid NewTableSpace)
 		if (isNull)
 			reloptions = (Datum) 0;
 	}
-	AlterTableCreateToastTable(OIDNewHeap, reloptions);
+	AlterTableCreateToastTable(OIDNewHeap, reloptions, false);
 
 	if (OidIsValid(toastid))
 		ReleaseSysCache(tuple);

src/backend/commands/tablecmds.c

@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/commands/tablecmds.c,v 1.281 2009/03/31 22:12:47 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/backend/commands/tablecmds.c,v 1.282 2009/05/07 22:58:28 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -2584,7 +2584,7 @@ ATRewriteCatalogs(List **wqueue)
 			(tab->subcmds[AT_PASS_ADD_COL] ||
 			 tab->subcmds[AT_PASS_ALTER_TYPE] ||
 			 tab->subcmds[AT_PASS_COL_ATTRS]))
-			AlterTableCreateToastTable(tab->relid, (Datum) 0);
+			AlterTableCreateToastTable(tab->relid, (Datum) 0, false);
 	}
 }
 

src/backend/executor/execMain.c

@@ -26,7 +26,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/executor/execMain.c,v 1.323 2009/02/08 18:02:27 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/backend/executor/execMain.c,v 1.324 2009/05/07 22:58:28 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -2953,7 +2953,7 @@ OpenIntoRel(QueryDesc *queryDesc)
 
 	(void) heap_reloptions(RELKIND_TOASTVALUE, reloptions, true);
 
-	AlterTableCreateToastTable(intoRelationId, reloptions);
+	AlterTableCreateToastTable(intoRelationId, reloptions, false);
 
 	/*
 	 * And open the constructed table for writing.

src/backend/tcop/utility.c

@@ -10,7 +10,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/tcop/utility.c,v 1.306 2009/02/02 19:31:39 alvherre Exp $
+ *	  $PostgreSQL: pgsql/src/backend/tcop/utility.c,v 1.307 2009/05/07 22:58:28 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -442,10 +442,13 @@ ProcessUtility(Node *parsetree,
 															"toast",
 															validnsps,
 															true, false);
-						(void) heap_reloptions(RELKIND_TOASTVALUE, toast_options,
+						(void) heap_reloptions(RELKIND_TOASTVALUE,
+											   toast_options,
 											   true);
 
-						AlterTableCreateToastTable(relOid, toast_options);
+						AlterTableCreateToastTable(relOid,
+												   toast_options,
+												   false);
 					}
 					else
 					{

src/include/catalog/toasting.h

@@ -7,7 +7,7 @@
  * Portions Copyright (c) 1996-2009, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $PostgreSQL: pgsql/src/include/catalog/toasting.h,v 1.6 2009/02/02 19:31:40 alvherre Exp $
+ * $PostgreSQL: pgsql/src/include/catalog/toasting.h,v 1.7 2009/05/07 22:58:28 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -17,7 +17,7 @@
 /*
  * toasting.c prototypes
  */
-extern void AlterTableCreateToastTable(Oid relOid, Datum reloptions);
+extern void AlterTableCreateToastTable(Oid relOid, Datum reloptions, bool force);
 extern void BootstrapToastTable(char *relName,
 					Oid toastOid, Oid toastIndexOid);