Allow extracting and parsing of reloptions from a bare pg_class tuple, and

refactor the relcache code that used to do that.  This allows other callers
(particularly autovacuum) to do the same without necessarily having to open
and lock a table.

Author: alvherre

src/backend/access/common/reloptions.c

@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/access/common/reloptions.c,v 1.18 2009/01/12 21:02:14 alvherre Exp $
+ *	  $PostgreSQL: pgsql/src/backend/access/common/reloptions.c,v 1.19 2009/01/26 19:41:06 alvherre Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -558,6 +558,53 @@ untransformRelOptions(Datum options)
 	return result;
 }
 
+/*
+ * Extract and parse reloptions from a pg_class tuple.
+ *
+ * This is a low-level routine, expected to be used by relcache code and
+ * callers that do not have a table's relcache entry (e.g. autovacuum).  For
+ * other uses, consider grabbing the rd_options pointer from the relcache entry
+ * instead.
+ *
+ * tupdesc is pg_class' tuple descriptor.  amoptions is the amoptions regproc
+ * in the case of the tuple corresponding to an index, or InvalidOid otherwise.
+ */
+bytea *
+extractRelOptions(HeapTuple tuple, TupleDesc tupdesc, Oid amoptions)
+{
+	bytea  *options;
+	bool	isnull;
+	Datum	datum;
+	Form_pg_class	classForm;
+
+	datum = fastgetattr(tuple,
+						Anum_pg_class_reloptions,
+						tupdesc,
+						&isnull);
+	if (isnull)
+		return NULL;
+
+	classForm = (Form_pg_class) GETSTRUCT(tuple);
+
+	/* Parse into appropriate format; don't error out here */
+	switch (classForm->relkind)
+	{
+		case RELKIND_RELATION:
+		case RELKIND_TOASTVALUE:
+		case RELKIND_UNCATALOGED:
+			options = heap_reloptions(classForm->relkind, datum, false);
+			break;
+		case RELKIND_INDEX:
+			options = index_reloptions(amoptions, datum, false);
+			break;
+		default:
+			Assert(false);		/* can't get here */
+			options = NULL;		/* keep compiler quiet */
+			break;
+	}
+	
+	return options;
+}
 
 /*
  * Interpret reloptions that are given in text-array format.

src/backend/utils/cache/relcache.c

@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/utils/cache/relcache.c,v 1.282 2009/01/22 20:16:06 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/backend/utils/cache/relcache.c,v 1.283 2009/01/26 19:41:06 alvherre Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -351,8 +351,6 @@ AllocateRelationDesc(Relation relation, Form_pg_class relp)
 static void
 RelationParseRelOptions(Relation relation, HeapTuple tuple)
 {
-	Datum		datum;
-	bool		isnull;
 	bytea	   *options;
 
 	relation->rd_options = NULL;
@@ -374,31 +372,10 @@ RelationParseRelOptions(Relation relation, HeapTuple tuple)
 	 * we might not have any other for pg_class yet (consider executing this
 	 * code for pg_class itself)
 	 */
-	datum = fastgetattr(tuple,
-						Anum_pg_class_reloptions,
-						GetPgClassDescriptor(),
-						&isnull);
-	if (isnull)
-		return;
-
-	/* Parse into appropriate format; don't error out here */
-	switch (relation->rd_rel->relkind)
-	{
-		case RELKIND_RELATION:
-		case RELKIND_TOASTVALUE:
-		case RELKIND_UNCATALOGED:
-			options = heap_reloptions(relation->rd_rel->relkind, datum,
-									  false);
-			break;
-		case RELKIND_INDEX:
-			options = index_reloptions(relation->rd_am->amoptions, datum,
-									   false);
-			break;
-		default:
-			Assert(false);		/* can't get here */
-			options = NULL;		/* keep compiler quiet */
-			break;
-	}
+	options = extractRelOptions(tuple,
+								GetPgClassDescriptor(),
+								relation->rd_rel->relkind == RELKIND_INDEX ?
+								relation->rd_am->amoptions : InvalidOid);
 
 	/* Copy parsed data into CacheMemoryContext */
 	if (options)

src/include/access/reloptions.h

@@ -11,13 +11,14 @@
  * Portions Copyright (c) 1996-2009, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $PostgreSQL: pgsql/src/include/access/reloptions.h,v 1.10 2009/01/12 21:02:15 alvherre Exp $
+ * $PostgreSQL: pgsql/src/include/access/reloptions.h,v 1.11 2009/01/26 19:41:06 alvherre Exp $
  *
  *-------------------------------------------------------------------------
  */
 #ifndef RELOPTIONS_H
 #define RELOPTIONS_H
 
+#include "access/htup.h"
 #include "nodes/pg_list.h"
 
 /* types supported by reloptions */
@@ -241,6 +242,8 @@ extern void add_string_reloption(int kind, char *name, char *desc,
 extern Datum transformRelOptions(Datum oldOptions, List *defList,
 					bool ignoreOids, bool isReset);
 extern List *untransformRelOptions(Datum options);
+extern bytea *extractRelOptions(HeapTuple tuple, TupleDesc tupdesc,
+				  Oid amoptions);
 extern relopt_value *parseRelOptions(Datum options, bool validate,
 				relopt_kind kind, int *numrelopts);
 extern void *allocateReloptStruct(Size base, relopt_value *options,