Add LOCK A,B,C functionality as LOCK A;LOCK B;LOCK C; as agreed.

Neil Padgett

Author: bmomjian

doc/src/sgml/ref/lock.sgml

@@ -1,5 +1,5 @@
 <!--
-$Header: /cvsroot/pgsql/doc/src/sgml/ref/lock.sgml,v 1.24 2001/07/09 22:18:33 tgl Exp $
+$Header: /cvsroot/pgsql/doc/src/sgml/ref/lock.sgml,v 1.25 2001/08/04 19:38:59 momjian Exp $
 Postgres documentation
 -->
 
@@ -15,16 +15,16 @@ Postgres documentation
    LOCK
   </refname>
   <refpurpose>
-   Explicitly lock a table inside a transaction
+   Explicitly lock a table / tables inside a transaction
   </refpurpose>
  </refnamediv>
  <refsynopsisdiv>
   <refsynopsisdivinfo>
    <date>2001-07-09</date>
   </refsynopsisdivinfo>
   <synopsis>
-LOCK [ TABLE ] <replaceable class="PARAMETER">name</replaceable>
-LOCK [ TABLE ] <replaceable class="PARAMETER">name</replaceable> IN <replaceable class="PARAMETER">lockmode</replaceable> MODE
+LOCK [ TABLE ] <replaceable class="PARAMETER">name</replaceable> [,...]
+LOCK [ TABLE ] <replaceable class="PARAMETER">name</replaceable> [,...] IN <replaceable class="PARAMETER">lockmode</replaceable> MODE
 
 where <replaceable class="PARAMETER">lockmode</replaceable> is one of:
 
@@ -373,6 +373,7 @@ ERROR <replaceable class="PARAMETER">name</replaceable>: Table does not exist.
      An example for this rule was given previously when discussing the 
      use of SHARE ROW EXCLUSIVE mode rather than SHARE mode.
     </para>
+
    </listitem>
   </itemizedlist>
 
@@ -383,6 +384,12 @@ ERROR <replaceable class="PARAMETER">name</replaceable>: Table does not exist.
    </para>
   </note>
 
+  <para>
+   When locking multiple tables, the command LOCK a, b; is equivalent to LOCK
+   a; LOCK b;. The tables are locked one-by-one in the order specified in the
+   <command>LOCK</command> command.
+  </para>
+
   <refsect2 id="R2-SQL-LOCK-3">
    <refsect2info>
     <date>1999-06-08</date>
@@ -406,6 +413,7 @@ ERROR <replaceable class="PARAMETER">name</replaceable>: Table does not exist.
    <para>
     <command>LOCK</command> works only inside transactions.
    </para>
+
   </refsect2>
  </refsect1>
 

src/backend/commands/command.c

@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $Header: /cvsroot/pgsql/src/backend/commands/Attic/command.c,v 1.136 2001/07/16 05:06:57 tgl Exp $
+ *	  $Header: /cvsroot/pgsql/src/backend/commands/Attic/command.c,v 1.137 2001/08/04 19:38:59 momjian Exp $
  *
  * NOTES
  *	  The PerformAddAttribute() code, like most of the relation
@@ -1984,8 +1984,7 @@ needs_toast_table(Relation rel)
 		MAXALIGN(data_length);
 	return (tuple_length > TOAST_TUPLE_THRESHOLD);
 }
-
-
+	
 /*
  *
  * LOCK TABLE
@@ -1994,26 +1993,104 @@ needs_toast_table(Relation rel)
 void
 LockTableCommand(LockStmt *lockstmt)
 {
-	Relation	rel;
-	int			aclresult;
+	int         relCnt;
 
-	rel = heap_openr(lockstmt->relname, NoLock);
+	relCnt = length(lockstmt -> rellist);
 
-	if (rel->rd_rel->relkind != RELKIND_RELATION)
-		elog(ERROR, "LOCK TABLE: %s is not a table", lockstmt->relname);
+	/* Handle a single relation lock specially to avoid overhead on likely the
+	   most common case */
 
-	if (lockstmt->mode == AccessShareLock)
-		aclresult = pg_aclcheck(lockstmt->relname, GetUserId(), ACL_SELECT);
-	else
-		aclresult = pg_aclcheck(lockstmt->relname, GetUserId(),
-								ACL_UPDATE | ACL_DELETE);
+	if(relCnt == 1)
+	{
+
+		/* Locking a single table */
+
+		Relation	rel;
+		int			aclresult;
+		char *relname;
+
+		relname = strVal(lfirst(lockstmt->rellist));
+
+		freeList(lockstmt->rellist);
+
+		rel = heap_openr(relname, NoLock);
+
+		if (rel->rd_rel->relkind != RELKIND_RELATION)
+			elog(ERROR, "LOCK TABLE: %s is not a table", relname);
+
+		if (lockstmt->mode == AccessShareLock)
+			aclresult = pg_aclcheck(relname, GetUserId(),
+									ACL_SELECT);
+		else
+			aclresult = pg_aclcheck(relname, GetUserId(),
+									ACL_UPDATE | ACL_DELETE);
+
+		if (aclresult != ACLCHECK_OK)
+			elog(ERROR, "LOCK TABLE: permission denied");
+
+		LockRelation(rel, lockstmt->mode);
+
+		pfree(relname);
+
+		heap_close(rel, NoLock);	/* close rel, keep lock */
+	} 
+	else 
+	{
+		List *p;
+		Relation *RelationArray;
+		Relation *pRel;
 
-	if (aclresult != ACLCHECK_OK)
-		elog(ERROR, "LOCK TABLE: permission denied");
+		/* Locking multiple tables */
 
-	LockRelation(rel, lockstmt->mode);
+		/* Create an array of relations */
 
-	heap_close(rel, NoLock);	/* close rel, keep lock */
+		RelationArray = palloc(relCnt * sizeof(Relation));
+		pRel = RelationArray;
+
+		/* Iterate over the list and populate the relation array */
+
+		foreach(p, lockstmt->rellist)
+		{
+			char* relname = strVal(lfirst(p));
+			int			aclresult;
+
+			*pRel = heap_openr(relname, NoLock);
+
+			if ((*pRel)->rd_rel->relkind != RELKIND_RELATION)
+				elog(ERROR, "LOCK TABLE: %s is not a table", 
+					 relname);
+
+			if (lockstmt->mode == AccessShareLock)
+				aclresult = pg_aclcheck(relname, GetUserId(),
+										ACL_SELECT);
+			else
+				aclresult = pg_aclcheck(relname, GetUserId(),
+										ACL_UPDATE | ACL_DELETE);
+
+			if (aclresult != ACLCHECK_OK)
+				elog(ERROR, "LOCK TABLE: permission denied");
+
+			pRel++;
+			pfree(relname);
+		}
+
+		/* Now, lock all the relations, closing each after it is locked
+		   (Keeping the locks)
+		 */
+
+		for(pRel = RelationArray;
+			pRel < RelationArray + relCnt;
+			pRel++)
+			{
+				LockRelation(*pRel, lockstmt->mode);
+
+				heap_close(*pRel, NoLock);
+			}
+
+		/* Free the relation array */
+
+		pfree(RelationArray);
+	}
 }
 
 

src/backend/nodes/copyfuncs.c

@@ -15,7 +15,7 @@
  * Portions Copyright (c) 1994, Regents of the University of California
  *
  * IDENTIFICATION
- *	  $Header: /cvsroot/pgsql/src/backend/nodes/copyfuncs.c,v 1.148 2001/07/16 19:07:37 momjian Exp $
+ *	  $Header: /cvsroot/pgsql/src/backend/nodes/copyfuncs.c,v 1.149 2001/08/04 19:38:59 momjian Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -2425,8 +2425,8 @@ _copyLockStmt(LockStmt *from)
 {
 	LockStmt   *newnode = makeNode(LockStmt);
 
-	if (from->relname)
-		newnode->relname = pstrdup(from->relname);
+	Node_Copy(from, newnode, rellist);
+	
 	newnode->mode = from->mode;
 
 	return newnode;

src/backend/nodes/equalfuncs.c

@@ -20,7 +20,7 @@
  * Portions Copyright (c) 1994, Regents of the University of California
  *
  * IDENTIFICATION
- *	  $Header: /cvsroot/pgsql/src/backend/nodes/equalfuncs.c,v 1.96 2001/07/16 19:07:38 momjian Exp $
+ *	  $Header: /cvsroot/pgsql/src/backend/nodes/equalfuncs.c,v 1.97 2001/08/04 19:38:59 momjian Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -1283,7 +1283,7 @@ _equalDropUserStmt(DropUserStmt *a, DropUserStmt *b)
 static bool
 _equalLockStmt(LockStmt *a, LockStmt *b)
 {
-	if (!equalstr(a->relname, b->relname))
+	if (!equal(a->rellist, b->rellist))
 		return false;
 	if (a->mode != b->mode)
 		return false;

src/backend/parser/gram.y

@@ -11,7 +11,7 @@
  *
  *
  * IDENTIFICATION
- *	  $Header: /cvsroot/pgsql/src/backend/parser/gram.y,v 2.238 2001/07/16 19:07:40 momjian Exp $
+ *	  $Header: /cvsroot/pgsql/src/backend/parser/gram.y,v 2.239 2001/08/04 19:38:59 momjian Exp $
  *
  * HISTORY
  *	  AUTHOR			DATE			MAJOR EVENT
@@ -3280,11 +3280,11 @@ DeleteStmt:  DELETE FROM relation_expr where_clause
 				}
 		;
 
-LockStmt:	LOCK_P opt_table relation_name opt_lock
+LockStmt:	LOCK_P opt_table relation_name_list opt_lock
 				{
 					LockStmt *n = makeNode(LockStmt);
 
-					n->relname = $3;
+					n->rellist = $3;
 					n->mode = $4;
 					$$ = (Node *)n;
 				}

src/include/nodes/parsenodes.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: parsenodes.h,v 1.136 2001/07/16 19:07:40 momjian Exp $
+ * $Id: parsenodes.h,v 1.137 2001/08/04 19:38:59 momjian Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -760,7 +760,7 @@ typedef struct VariableResetStmt
 typedef struct LockStmt
 {
 	NodeTag		type;
-	char	   *relname;		/* relation to lock */
+	List	   *rellist;		/* relations to lock */
 	int			mode;			/* lock mode */
 } LockStmt;
 

src/interfaces/ecpg/preproc/preproc.y

@@ -2421,7 +2421,7 @@ DeleteStmt:  DELETE FROM relation_expr where_clause
 				}
 		;
 
-LockStmt:  LOCK_P opt_table relation_name opt_lock
+LockStmt:  LOCK_P opt_table relation_name_list opt_lock
 				{
 					$$ = cat_str(4, make_str("lock"), $2, $3, $4);
 				}