Code review for NOWAIT patch: downgrade NOWAIT from fully reserved keyword

to unreserved keyword, use ereport not elog, assign a separate error code
for 'could not obtain lock' so that applications will be able to detect
that case cleanly.

doc/src/sgml/errcodes.sgml

-<!-- $PostgreSQL: pgsql/doc/src/sgml/errcodes.sgml,v 1.8 2004/08/24 00:06:50 neilc Exp $ -->
+<!-- $PostgreSQL: pgsql/doc/src/sgml/errcodes.sgml,v 1.9 2004/10/01 16:39:46 tgl Exp $ -->
 
 <appendix id="errcodes-appendix">
  <title><productname>PostgreSQL</productname> Error Codes</title>
@@ -1099,6 +1099,11 @@
 <entry>CANT CHANGE RUNTIME PARAM</entry>
 </row>
 
+<row>
+<entry><literal>55P03</literal></entry>
+<entry>LOCK NOT AVAILABLE</entry>
+</row>
+
 
 <row>
 <entry>Class 57</entry>

doc/src/sgml/ref/lock.sgml

 <!--
-$PostgreSQL: pgsql/doc/src/sgml/ref/lock.sgml,v 1.42 2004/03/12 00:52:23 neilc Exp $
+$PostgreSQL: pgsql/doc/src/sgml/ref/lock.sgml,v 1.43 2004/10/01 16:39:47 tgl Exp $
 PostgreSQL documentation
 -->
 
@@ -37,7 +37,7 @@ where <replaceable class="PARAMETER">lockmode</replaceable> is one of:
    if necessary for any conflicting locks to be released.  If
    <literal>NOWAIT</literal> is specified, <command>LOCK
    TABLE</command> does not wait to acquire the desired lock: if it
-   cannot be immediately acquired, the transaction is aborted and an
+   cannot be acquired immediately, the command is aborted and an
    error is emitted.  Once obtained, the lock is held for the
    remainder of the current transaction.  (There is no <command>UNLOCK
    TABLE</command> command; locks are always released at transaction

src/backend/access/heap/heapam.c

@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/access/heap/heapam.c,v 1.176 2004/09/17 18:09:55 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/backend/access/heap/heapam.c,v 1.177 2004/10/01 16:39:54 tgl Exp $
  *
  *
  * INTERFACE ROUTINES
@@ -465,6 +465,13 @@ relation_open(Oid relationId, LOCKMODE lockmode)
 	return r;
 }
 
+/* ----------------
+ *		conditional_relation_open - open with option not to wait
+ *
+ *		As above, but if nowait is true, then throw an error rather than
+ *		waiting when the lock is not immediately obtainable.
+ * ----------------
+ */
 Relation
 conditional_relation_open(Oid relationId, LOCKMODE lockmode, bool nowait)
 {
@@ -483,7 +490,10 @@ conditional_relation_open(Oid relationId, LOCKMODE lockmode, bool nowait)
 		if (nowait)
 		{
 			if (!ConditionalLockRelation(r, lockmode))
-				elog(ERROR, "could not acquire relation lock");
+				ereport(ERROR,
+						(errcode(ERRCODE_LOCK_NOT_AVAILABLE),
+						 errmsg("could not obtain lock on \"%s\"",
+								RelationGetRelationName(r))));
 		}
 		else
 			LockRelation(r, lockmode);

src/backend/parser/gram.y

@@ -11,7 +11,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/parser/gram.y,v 2.477 2004/09/30 00:24:20 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/backend/parser/gram.y,v 2.478 2004/10/01 16:39:59 tgl Exp $
  *
  * HISTORY
  *	  AUTHOR			DATE			MAJOR EVENT
@@ -7727,6 +7727,7 @@ unreserved_keyword:
 			| NOCREATEUSER
 			| NOTHING
 			| NOTIFY
+			| NOWAIT
 			| OBJECT_P
 			| OF
 			| OIDS
@@ -7944,7 +7945,6 @@ reserved_keyword:
 			| LOCALTIMESTAMP
 			| NEW
 			| NOT
-			| NOWAIT
 			| NULL_P
 			| OFF
 			| OFFSET

src/include/utils/errcodes.h

@@ -11,7 +11,7 @@
  *
  * Copyright (c) 2003, PostgreSQL Global Development Group
  *
- * $PostgreSQL: pgsql/src/include/utils/errcodes.h,v 1.15 2004/08/29 05:06:58 momjian Exp $
+ * $PostgreSQL: pgsql/src/include/utils/errcodes.h,v 1.16 2004/10/01 16:40:04 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -308,6 +308,7 @@
 #define ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE	MAKE_SQLSTATE('5','5', '0','0','0')
 #define ERRCODE_OBJECT_IN_USE				MAKE_SQLSTATE('5','5', '0','0','6')
 #define ERRCODE_CANT_CHANGE_RUNTIME_PARAM	MAKE_SQLSTATE('5','5', 'P','0','2')
+#define ERRCODE_LOCK_NOT_AVAILABLE			MAKE_SQLSTATE('5','5', 'P','0','3')
 
 /* Class 57 - Operator Intervention (class borrowed from DB2) */
 #define ERRCODE_OPERATOR_INTERVENTION		MAKE_SQLSTATE('5','7', '0','0','0')

src/pl/plpgsql/src/plerrcodes.h

@@ -9,7 +9,7 @@
  *
  * Copyright (c) 2003, PostgreSQL Global Development Group
  *
- * $PostgreSQL: pgsql/src/pl/plpgsql/src/plerrcodes.h,v 1.4 2004/08/29 05:07:01 momjian Exp $
+ * $PostgreSQL: pgsql/src/pl/plpgsql/src/plerrcodes.h,v 1.5 2004/10/01 16:40:05 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -659,6 +659,10 @@
 	"cant_change_runtime_param", ERRCODE_CANT_CHANGE_RUNTIME_PARAM
 },
 
+{
+	"lock_not_available", ERRCODE_LOCK_NOT_AVAILABLE
+},
+
 {
 	"operator_intervention", ERRCODE_OPERATOR_INTERVENTION
 },