Improve the representation of FOR UPDATE/FOR SHARE so that we can

support both FOR UPDATE and FOR SHARE in one command, as well as both
NOWAIT and normal WAIT behavior.  The more general code is actually
simpler and cleaner.

1 files changed, 62 insertions, 51 deletions

diff --git a/src/backend/parser/analyze.c b/src/backend/parser/analyze.c
index d69c0f17864..566c9a0488d 100644
--- a/src/backend/parser/analyze.c
+++ b/src/backend/parser/analyze.c
@@ -6,7 +6,7 @@
  * Portions Copyright (c) 1996-2006, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- *	$PostgreSQL: pgsql/src/backend/parser/analyze.c,v 1.333 2006/04/22 01:25:59 tgl Exp $
+ *	$PostgreSQL: pgsql/src/backend/parser/analyze.c,v 1.334 2006/04/30 18:30:39 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -1805,6 +1805,7 @@ transformSelectStmt(ParseState *pstate, SelectStmt *stmt)
 {
 	Query	   *qry = makeNode(Query);
 	Node	   *qual;
+	ListCell   *l;
 
 	qry->commandType = CMD_SELECT;
 
@@ -1870,8 +1871,10 @@ transformSelectStmt(ParseState *pstate, SelectStmt *stmt)
 	if (pstate->p_hasAggs || qry->groupClause || qry->havingQual)
 		parseCheckAggregates(pstate, qry);
 
-	if (stmt->lockingClause)
-		transformLockingClause(qry, stmt->lockingClause);
+	foreach(l, stmt->lockingClause)
+	{
+		transformLockingClause(qry, (LockingClause *) lfirst(l));
+	}
 
 	return qry;
 }
@@ -1899,10 +1902,11 @@ transformSetOperationStmt(ParseState *pstate, SelectStmt *stmt)
 	List	   *sortClause;
 	Node	   *limitOffset;
 	Node	   *limitCount;
-	LockingClause *lockingClause;
+	List	   *lockingClause;
 	Node	   *node;
 	ListCell   *left_tlist,
-			   *dtlist;
+			   *dtlist,
+			   *l;
 	List	   *targetvars,
 			   *targetnames,
 			   *sv_relnamespace,
@@ -1942,7 +1946,7 @@ transformSetOperationStmt(ParseState *pstate, SelectStmt *stmt)
 	stmt->sortClause = NIL;
 	stmt->limitOffset = NULL;
 	stmt->limitCount = NULL;
-	stmt->lockingClause = NULL;
+	stmt->lockingClause = NIL;
 
 	/* We don't support FOR UPDATE/SHARE with set ops at the moment. */
 	if (lockingClause)
@@ -2084,8 +2088,10 @@ transformSetOperationStmt(ParseState *pstate, SelectStmt *stmt)
 	if (pstate->p_hasAggs || qry->groupClause || qry->havingQual)
 		parseCheckAggregates(pstate, qry);
 
-	if (lockingClause)
-		transformLockingClause(qry, lockingClause);
+	foreach(l, lockingClause)
+	{
+		transformLockingClause(qry, (LockingClause *) lfirst(l));
+	}
 
 	return qry;
 }
@@ -2743,44 +2749,34 @@ transformExecuteStmt(ParseState *pstate, ExecuteStmt *stmt)
 
 /* exported so planner can check again after rewriting, query pullup, etc */
 void
-CheckSelectLocking(Query *qry, bool forUpdate)
+CheckSelectLocking(Query *qry)
 {
-	const char *operation;
-
-	if (forUpdate)
-		operation = "SELECT FOR UPDATE";
-	else
-		operation = "SELECT FOR SHARE";
-
 	if (qry->setOperations)
 		ereport(ERROR,
 				(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
-		/* translator: %s is a SQL command, like SELECT FOR UPDATE */
-		errmsg("%s is not allowed with UNION/INTERSECT/EXCEPT", operation)));
+				 errmsg("SELECT FOR UPDATE/SHARE is not allowed with UNION/INTERSECT/EXCEPT")));
 	if (qry->distinctClause != NIL)
 		ereport(ERROR,
 				(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
-		/* translator: %s is a SQL command, like SELECT FOR UPDATE */
-			   errmsg("%s is not allowed with DISTINCT clause", operation)));
+				 errmsg("SELECT FOR UPDATE/SHARE is not allowed with DISTINCT clause")));
 	if (qry->groupClause != NIL)
 		ereport(ERROR,
 				(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
-		/* translator: %s is a SQL command, like SELECT FOR UPDATE */
-			   errmsg("%s is not allowed with GROUP BY clause", operation)));
+				 errmsg("SELECT FOR UPDATE/SHARE is not allowed with GROUP BY clause")));
 	if (qry->havingQual != NULL)
 		ereport(ERROR,
 				(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
-		/* translator: %s is a SQL command, like SELECT FOR UPDATE */
-				 errmsg("%s is not allowed with HAVING clause", operation)));
+				 errmsg("SELECT FOR UPDATE/SHARE is not allowed with HAVING clause")));
 	if (qry->hasAggs)
 		ereport(ERROR,
 				(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
-		/* translator: %s is a SQL command, like SELECT FOR UPDATE */
-		   errmsg("%s is not allowed with aggregate functions", operation)));
+				 errmsg("SELECT FOR UPDATE/SHARE is not allowed with aggregate functions")));
 }
 
 /*
- * Convert FOR UPDATE/SHARE name list into rowMarks list of integer relids
+ * Transform a FOR UPDATE/SHARE clause
+ *
+ * This basically involves replacing names by integer relids.
  *
  * NB: if you need to change this, see also markQueryForLocking()
  * in rewriteHandler.c.
@@ -2789,35 +2785,18 @@ static void
 transformLockingClause(Query *qry, LockingClause *lc)
 {
 	List	   *lockedRels = lc->lockedRels;
-	List	   *rowMarks;
 	ListCell   *l;
 	ListCell   *rt;
 	Index		i;
 	LockingClause *allrels;
 
-	if (qry->rowMarks)
-	{
-		if (lc->forUpdate != qry->forUpdate)
-			ereport(ERROR,
-					(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
-			errmsg("cannot use both FOR UPDATE and FOR SHARE in one query")));
-		if (lc->nowait != qry->rowNoWait)
-			ereport(ERROR,
-					(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
-					 errmsg("cannot use both wait and NOWAIT in one query")));
-	}
-	qry->forUpdate = lc->forUpdate;
-	qry->rowNoWait = lc->nowait;
-
-	CheckSelectLocking(qry, lc->forUpdate);
+	CheckSelectLocking(qry);
 
 	/* make a clause we can pass down to subqueries to select all rels */
 	allrels = makeNode(LockingClause);
 	allrels->lockedRels = NIL;	/* indicates all rels */
 	allrels->forUpdate = lc->forUpdate;
-	allrels->nowait = lc->nowait;
-
-	rowMarks = qry->rowMarks;
+	allrels->noWait = lc->noWait;
 
 	if (lockedRels == NIL)
 	{
@@ -2831,8 +2810,7 @@ transformLockingClause(Query *qry, LockingClause *lc)
 			switch (rte->rtekind)
 			{
 				case RTE_RELATION:
-					/* use list_append_unique to avoid duplicates */
-					rowMarks = list_append_unique_int(rowMarks, i);
+					applyLockingClause(qry, i, lc->forUpdate, lc->noWait);
 					rte->requiredPerms |= ACL_SELECT_FOR_UPDATE;
 					break;
 				case RTE_SUBQUERY:
@@ -2867,8 +2845,8 @@ transformLockingClause(Query *qry, LockingClause *lc)
 					switch (rte->rtekind)
 					{
 						case RTE_RELATION:
-							/* use list_append_unique to avoid duplicates */
-							rowMarks = list_append_unique_int(rowMarks, i);
+							applyLockingClause(qry, i,
+											   lc->forUpdate, lc->noWait);
 							rte->requiredPerms |= ACL_SELECT_FOR_UPDATE;
 							break;
 						case RTE_SUBQUERY:
@@ -2909,8 +2887,41 @@ transformLockingClause(Query *qry, LockingClause *lc)
 								relname)));
 		}
 	}
+}
+
+/*
+ * Record locking info for a single rangetable item
+ */
+void
+applyLockingClause(Query *qry, Index rtindex, bool forUpdate, bool noWait)
+{
+	RowMarkClause *rc;
+
+	/* Check for pre-existing entry for same rtindex */
+	if ((rc = get_rowmark(qry, rtindex)) != NULL)
+	{
+		/*
+		 * If the same RTE is specified both FOR UPDATE and FOR SHARE,
+		 * treat it as FOR UPDATE.  (Reasonable, since you can't take
+		 * both a shared and exclusive lock at the same time; it'll
+		 * end up being exclusive anyway.)
+		 *
+		 * We also consider that NOWAIT wins if it's specified both ways.
+		 * This is a bit more debatable but raising an error doesn't
+		 * seem helpful.  (Consider for instance SELECT FOR UPDATE NOWAIT
+		 * from a view that internally contains a plain FOR UPDATE spec.)
+		 */
+		rc->forUpdate |= forUpdate;
+		rc->noWait |= noWait;
+		return;
+	}
 
-	qry->rowMarks = rowMarks;
+	/* Make a new RowMarkClause */
+	rc = makeNode(RowMarkClause);
+	rc->rti = rtindex;
+	rc->forUpdate = forUpdate;
+	rc->noWait = noWait;
+	qry->rowMarks = lappend(qry->rowMarks, rc);
 }