Fix problem reported by Alex Korn: if a relation has been dropped and

recreated since the start of our transaction, our first reference to it
errored out because we'd try to reuse our old relcache entry for it.
Do this by accepting SI inval messages just before relcache search in
heap_openr, so that dead relcache entries will be flushed before we
search.  Also, break heap_open/openr into two pairs of routines,
relation_open(r) and heap_open(r).  The relation_open routines make
no tests on relkind and so can be used to open anything that has a
pg_class entry.  The heap_open routines are wrappers that add a relkind
test to preserve their established behavior.  Use the relation_open
routines in several places that had various kluge solutions for opening
rels that might be either heap or index rels.

Also, remove the old 'heap stats' code that's been superseded by Jan's
stats collector, and clean up some inconsistencies in error reporting
between the different types of ALTER TABLE.

1 files changed, 22 insertions, 29 deletions

diff --git a/src/backend/commands/command.c b/src/backend/commands/command.c
index b9cfee96e4f..93c52e1b334 100644
--- a/src/backend/commands/command.c
+++ b/src/backend/commands/command.c
@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $Header: /cvsroot/pgsql/src/backend/commands/Attic/command.c,v 1.148 2001/10/31 04:49:43 momjian Exp $
+ *	  $Header: /cvsroot/pgsql/src/backend/commands/Attic/command.c,v 1.149 2001/11/02 16:30:29 tgl Exp $
  *
  * NOTES
  *	  The PerformAddAttribute() code, like most of the relation
@@ -55,7 +55,6 @@
 
 static void drop_default(Oid relid, int16 attnum);
 static bool needs_toast_table(Relation rel);
-static bool is_relation(char *name);
 
 
 /* --------------------------------
@@ -554,9 +553,11 @@ AlterTableAlterColumnDefault(const char *relationName,
 #endif
 
 	rel = heap_openr(relationName, AccessExclusiveLock);
+
 	if (rel->rd_rel->relkind != RELKIND_RELATION)
 		elog(ERROR, "ALTER TABLE: relation \"%s\" is not a table",
 			 relationName);
+
 	myrelid = RelationGetRelid(rel);
 	heap_close(rel, NoLock);
 
@@ -721,9 +722,11 @@ AlterTableAlterColumnStatistics(const char *relationName,
 #endif
 
 	rel = heap_openr(relationName, AccessExclusiveLock);
+
 	if (rel->rd_rel->relkind != RELKIND_RELATION)
 		elog(ERROR, "ALTER TABLE: relation \"%s\" is not a table",
 			 relationName);
+
 	myrelid = RelationGetRelid(rel);
 	heap_close(rel, NoLock);	/* close rel, but keep lock! */
 
@@ -1192,12 +1195,16 @@ AlterTableAddConstraint(char *relationName,
 		elog(ERROR, "ALTER TABLE: permission denied");
 #endif
 
-	/* Disallow ADD CONSTRAINT on views, indexes, sequences, etc */
-	if (!is_relation(relationName))
-		elog(ERROR, "ALTER TABLE ADD CONSTRAINT: %s is not a table",
+	/*
+	 * Grab an exclusive lock on the target table, which we will NOT
+	 * release until end of transaction.
+	 */
+	rel = heap_openr(relationName, AccessExclusiveLock);
+
+	if (rel->rd_rel->relkind != RELKIND_RELATION)
+		elog(ERROR, "ALTER TABLE: relation \"%s\" is not a table",
 			 relationName);
 
-	rel = heap_openr(relationName, AccessExclusiveLock);
 	myrelid = RelationGetRelid(rel);
 
 	if (inh)
@@ -1686,7 +1693,7 @@ AlterTableDropConstraint(const char *relationName,
 
 	/* Disallow DROP CONSTRAINT on views, indexes, sequences, etc */
 	if (rel->rd_rel->relkind != RELKIND_RELATION)
-		elog(ERROR, "ALTER TABLE / DROP CONSTRAINT: %s is not a table",
+		elog(ERROR, "ALTER TABLE: relation \"%s\" is not a table",
 			 relationName);
 
 	/*
@@ -2053,7 +2060,6 @@ void
 LockTableCommand(LockStmt *lockstmt)
 {
 	List	   *p;
-	Relation	rel;
 
 	/*
 	 * Iterate over the list and open, lock, and close the relations one
@@ -2064,12 +2070,7 @@ LockTableCommand(LockStmt *lockstmt)
 	{
 		char	   *relname = strVal(lfirst(p));
 		int			aclresult;
-
-		rel = heap_openr(relname, NoLock);
-
-		if (rel->rd_rel->relkind != RELKIND_RELATION)
-			elog(ERROR, "LOCK TABLE: %s is not a table",
-				 relname);
+		Relation	rel;
 
 		if (lockstmt->mode == AccessShareLock)
 			aclresult = pg_aclcheck(relname, GetUserId(),
@@ -2081,21 +2082,13 @@ LockTableCommand(LockStmt *lockstmt)
 		if (aclresult != ACLCHECK_OK)
 			elog(ERROR, "LOCK TABLE: permission denied");
 
-		LockRelation(rel, lockstmt->mode);
-
-		heap_close(rel, NoLock);	/* close rel, keep lock */
-	}
-}
-
-
-static bool
-is_relation(char *name)
-{
-	Relation	rel = heap_openr(name, NoLock);
+		rel = relation_openr(relname, lockstmt->mode);
 
-	bool		retval = (rel->rd_rel->relkind == RELKIND_RELATION);
-
-	heap_close(rel, NoLock);
+		/* Currently, we only allow plain tables to be locked */
+		if (rel->rd_rel->relkind != RELKIND_RELATION)
+			elog(ERROR, "LOCK TABLE: %s is not a table",
+				 relname);
 
-	return retval;
+		relation_close(rel, NoLock);	/* close rel, keep lock */
+	}
 }