Modify sequence state storage to eliminate dangling-pointer problem

exemplified by bug #671.  Moving the storage to relcache turned out to
be a bad idea because relcache might decide to discard the info.  Instead,
open and close the relcache entry on each sequence operation, and use
a record of the current XID to discover whether we already hold
AccessShareLock on the sequence.

src/backend/access/transam/xact.c

@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $Header: /cvsroot/pgsql/src/backend/access/transam/xact.c,v 1.123 2002/05/21 22:05:53 tgl Exp $
+ *	  $Header: /cvsroot/pgsql/src/backend/access/transam/xact.c,v 1.124 2002/05/22 21:40:55 tgl Exp $
  *
  * NOTES
  *		Transaction aborts can now occur two ways:
@@ -166,7 +166,6 @@
 #include "catalog/index.h"
 #include "catalog/namespace.h"
 #include "commands/async.h"
-#include "commands/sequence.h"
 #include "commands/trigger.h"
 #include "executor/spi.h"
 #include "libpq/be-fsstubs.h"
@@ -947,7 +946,6 @@ CommitTransaction(void)
 	/* NOTIFY commit must also come before lower-level cleanup */
 	AtCommit_Notify();
 
-	CloseSequences();
 	AtEOXact_portals();
 
 	/* Here is where we really truly commit. */
@@ -1063,7 +1061,6 @@ AbortTransaction(void)
 	DeferredTriggerAbortXact();
 	lo_commit(false);			/* 'false' means it's abort */
 	AtAbort_Notify();
-	CloseSequences();
 	AtEOXact_portals();
 
 	/* Advertise the fact that we aborted in pg_clog. */

src/backend/commands/define.c

@@ -9,7 +9,7 @@
  *
  *
  * IDENTIFICATION
- *	  $Header: /cvsroot/pgsql/src/backend/commands/define.c,v 1.76 2002/04/15 05:22:03 tgl Exp $
+ *	  $Header: /cvsroot/pgsql/src/backend/commands/define.c,v 1.77 2002/05/22 21:40:55 tgl Exp $
  *
  * DESCRIPTION
  *	  The "DefineFoo" routines take the parse tree and pick out the
@@ -37,6 +37,7 @@
 
 #include "commands/defrem.h"
 #include "parser/parse_type.h"
+#include "utils/int8.h"
 
 
 /*
@@ -114,6 +115,34 @@ defGetNumeric(DefElem *def)
 	return 0;					/* keep compiler quiet */
 }
 
+/*
+ * Extract an int64 value from a DefElem.
+ */
+int64
+defGetInt64(DefElem *def)
+{
+	if (def->arg == NULL)
+		elog(ERROR, "Define: \"%s\" requires a numeric value",
+			 def->defname);
+	switch (nodeTag(def->arg))
+	{
+		case T_Integer:
+			return (int64) intVal(def->arg);
+		case T_Float:
+			/*
+			 * Values too large for int4 will be represented as Float
+			 * constants by the lexer.  Accept these if they are valid int8
+			 * strings.
+			 */
+			return DatumGetInt64(DirectFunctionCall1(int8in,
+									 CStringGetDatum(strVal(def->arg))));
+		default:
+			elog(ERROR, "Define: \"%s\" requires a numeric value",
+				 def->defname);
+	}
+	return 0;					/* keep compiler quiet */
+}
+
 /*
  * Extract a possibly-qualified name (as a List of Strings) from a DefElem.
  */

src/include/commands/defrem.h

@@ -7,7 +7,7 @@
  * Portions Copyright (c) 1996-2001, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $Id: defrem.h,v 1.37 2002/05/17 18:32:52 petere Exp $
+ * $Id: defrem.h,v 1.38 2002/05/22 21:40:55 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -54,12 +54,13 @@ extern void DefineDomain(CreateDomainStmt *stmt);
 extern void RemoveDomain(List *names, int behavior);
 
 
-/* support routines in define.c */
+/* support routines in commands/define.c */
 
 extern void case_translate_language_name(const char *input, char *output);
 
 extern char *defGetString(DefElem *def);
 extern double defGetNumeric(DefElem *def);
+extern int64 defGetInt64(DefElem *def);
 extern List *defGetQualifiedName(DefElem *def);
 extern TypeName *defGetTypeName(DefElem *def);
 extern int	defGetTypeLength(DefElem *def);

src/include/commands/sequence.h

@@ -6,7 +6,7 @@
  * Portions Copyright (c) 1996-2001, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $Id: sequence.h,v 1.19 2001/11/05 17:46:33 momjian Exp $
+ * $Id: sequence.h,v 1.20 2002/05/22 21:40:55 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -84,7 +84,6 @@ extern Datum setval(PG_FUNCTION_ARGS);
 extern Datum setval_and_iscalled(PG_FUNCTION_ARGS);
 
 extern void DefineSequence(CreateSeqStmt *stmt);
-extern void CloseSequences(void);
 
 extern void seq_redo(XLogRecPtr lsn, XLogRecord *rptr);
 extern void seq_undo(XLogRecPtr lsn, XLogRecord *rptr);