Fix bug noted by Bruce: FETCH in an already-aborted transaction block

would crash, due to premature invocation of SetQuerySnapshot().  Clean
up problems with handling of multiple queries by splitting
pg_parse_and_plan into two routines.  The old code would not, for
example, do the right thing with END; SELECT... submitted in one query
string when it had been in transaction abort state, because it'd decide
to skip planning the SELECT before it had executed the END.  New
arrangement is simpler and doesn't force caller to plan if only
parse+rewrite is needed.

1 files changed, 88 insertions, 131 deletions

diff --git a/src/backend/tcop/postgres.c b/src/backend/tcop/postgres.c
index a70418637f7..65b6bfbd6c0 100644
--- a/src/backend/tcop/postgres.c
+++ b/src/backend/tcop/postgres.c
@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $Header: /cvsroot/pgsql/src/backend/tcop/postgres.c,v 1.148 2000/03/23 23:16:48 momjian Exp $
+ *	  $Header: /cvsroot/pgsql/src/backend/tcop/postgres.c,v 1.149 2000/04/04 21:44:39 tgl Exp $
  *
  * NOTES
  *	  this is the "main" module of the postgres backend and
@@ -377,22 +377,23 @@ ReadCommand(StringInfo inBuf)
 	return result;
 }
 
+
+/*
+ * Parse a query string and pass it through the rewriter.
+ *
+ * A list of Query nodes is returned, since the string might contain
+ * multiple queries and/or the rewriter might expand one query to several.
+ */
 List *
-pg_parse_and_plan(char *query_string,	/* string to execute */
-				  Oid *typev,	/* argument types */
-				  int nargs,	/* number of arguments */
-				  List **queryListP,	/* returned pointer to the parse
-										 * trees */
-				  CommandDest dest,		/* where results should go */
-				  bool aclOverride)
+pg_parse_and_rewrite(char *query_string,	/* string to execute */
+					 Oid *typev,			/* argument types */
+					 int nargs,				/* number of arguments */
+					 bool aclOverride)
 {
-	List	   *querytree_list = NIL;
-	List	   *plan_list = NIL;
+	List	   *querytree_list;
 	List	   *querytree_list_item;
 	Query	   *querytree;
-	Plan	   *plan;
 	List	   *new_list;
-	List	   *rewritten;
 
 	if (DebugPrintQuery)
 	{
@@ -448,15 +449,16 @@ pg_parse_and_plan(char *query_string,	/* string to execute */
 		else
 		{
 			/* rewrite regular queries */
-			rewritten = QueryRewrite(querytree);
+			List *rewritten = QueryRewrite(querytree);
 			new_list = nconc(new_list, rewritten);
 		}
 	}
 
 	querytree_list = new_list;
 
-	/*
-	 * Override ACL checking if requested
+	/* ----------------
+	 *	(3) If ACL override is requested, mark queries for no ACL check.
+	 * ----------------
 	 */
 	if (aclOverride)
 	{
@@ -503,87 +505,54 @@ pg_parse_and_plan(char *query_string,	/* string to execute */
 		}
 	}
 
-	foreach(querytree_list_item, querytree_list)
-	{
-		querytree = (Query *) lfirst(querytree_list_item);
-
-		/*
-		 * For each query that isn't a utility invocation, generate a
-		 * plan.
-		 */
-
-		if (querytree->commandType != CMD_UTILITY)
-		{
+	return querytree_list;
+}
 
-			if (IsAbortedTransactionBlockState())
-			{
-				/* ----------------
-				 *	 the EndCommand() stuff is to tell the frontend
-				 *	 that the command ended. -cim 6/1/90
-				 * ----------------
-				 */
-				char	   *tag = "*ABORT STATE*";
 
-				EndCommand(tag, dest);
+/* Generate a plan for a single query. */
+Plan *
+pg_plan_query(Query *querytree)
+{
+	Plan	   *plan;
 
-				elog(NOTICE, "(transaction aborted): %s",
-					 "queries ignored until END");
+	/* Utility commands have no plans. */
+	if (querytree->commandType == CMD_UTILITY)
+		return NULL;
 
-				if (queryListP)
-					*queryListP = NIL;
-				return NIL;
-			}
+	if (ShowPlannerStats)
+		ResetUsage();
 
-			if (ShowPlannerStats)
-				ResetUsage();
+	/* call that optimizer */
+	plan = planner(querytree);
 
-			/* call that optimizer */
-			plan = planner(querytree);
+	if (ShowPlannerStats)
+	{
+		fprintf(stderr, "! Planner Stats:\n");
+		ShowUsage();
+	}
 
-			if (ShowPlannerStats)
-			{
-				fprintf(stderr, "! Planner Stats:\n");
-				ShowUsage();
-			}
-			plan_list = lappend(plan_list, plan);
-#ifdef INDEXSCAN_PATCH
-			/* ----------------
-			 *	Print plan if debugging.
-			 *	This has been moved here to get debugging output
-			 *	also for queries in functions.	DZ - 27-8-1996
-			 * ----------------
-			 */
-			if (DebugPrintPlan || DebugPPrintPlan)
-			{
-				if (DebugPPrintPlan)
-				{
-					TPRINTF(TRACE_PRETTY_PLAN, "plan:");
-					nodeDisplay(plan);
-				}
-				else
-				{
-					TPRINTF(TRACE_PLAN, "plan:");
-					printf("\n%s\n\n", nodeToString(plan));
-				}
-			}
-#endif
+	/* ----------------
+	 *	Print plan if debugging.
+	 * ----------------
+	 */
+	if (DebugPrintPlan || DebugPPrintPlan)
+	{
+		if (DebugPPrintPlan)
+		{
+			TPRINTF(TRACE_PRETTY_PLAN, "plan:");
+			nodeDisplay(plan);
 		}
-
-		/*
-		 * If the command is an utility append a null plan. This is needed
-		 * to keep the plan_list aligned with the querytree_list or the
-		 * function executor will crash.  DZ - 30-8-1996
-		 */
 		else
-			plan_list = lappend(plan_list, NULL);
+		{
+			TPRINTF(TRACE_PLAN, "plan:");
+			printf("\n%s\n\n", nodeToString(plan));
+		}
 	}
 
-	if (queryListP)
-		*queryListP = querytree_list;
-
-	return plan_list;
+	return plan;
 }
 
+
 /* ----------------------------------------------------------------
  *		pg_exec_query()
  *
@@ -620,39 +589,31 @@ pg_exec_query_dest(char *query_string,	/* string to execute */
 										 * of superusers */
 {
 	List	   *querytree_list;
-	List	   *plan_list;
-	Query	   *querytree;
-	Plan	   *plan;
-	int			j;
 
-	/* plan the queries */
-	plan_list = pg_parse_and_plan(query_string, NULL, 0,
-								  &querytree_list, dest, aclOverride);
-
-	/* if we got a cancel signal whilst planning, quit */
-	if (QueryCancel)
-		CancelQuery();
-
-	/* OK, do it to it! */
+	/* parse and rewrite the queries */
+	querytree_list = pg_parse_and_rewrite(query_string, NULL, 0,
+										  aclOverride);
 
 	/*
 	 * NOTE: we do not use "foreach" here because we want to be sure the
-	 * list pointers have been advanced before the query is executed. We
+	 * list pointer has been advanced before the query is executed. We
 	 * need to do that because VACUUM has a nasty little habit of doing
 	 * CommitTransactionCommand at startup, and that will release the
-	 * memory holding our parse/plan lists :-(.  This needs a better
+	 * memory holding our parse list :-(.  This needs a better
 	 * solution --- currently, the code will crash if someone submits
 	 * "vacuum; something-else" in a single query string.  But memory
 	 * allocation needs redesigned anyway, so this will have to do for
 	 * now.
 	 */
-
 	while (querytree_list)
 	{
-		querytree = (Query *) lfirst(querytree_list);
+		Query	   *querytree = (Query *) lfirst(querytree_list);
+
 		querytree_list = lnext(querytree_list);
-		plan = (Plan *) lfirst(plan_list);
-		plan_list = lnext(plan_list);
+
+		/* if we got a cancel signal in parsing or prior command, quit */
+		if (QueryCancel)
+			CancelQuery();
 
 		if (querytree->commandType == CMD_UTILITY)
 		{
@@ -668,42 +629,38 @@ pg_exec_query_dest(char *query_string,	/* string to execute */
 			else if (Verbose)
 				TPRINTF(TRACE_VERBOSE, "ProcessUtility");
 
-			/*
-			 * We have to set query SnapShot in the case of FETCH or COPY TO.
-			 */
-			if (nodeTag(querytree->utilityStmt) == T_FetchStmt ||
-				(nodeTag(querytree->utilityStmt) == T_CopyStmt && 
-				((CopyStmt *)(querytree->utilityStmt))->direction != FROM))
-				SetQuerySnapshot();
 			ProcessUtility(querytree->utilityStmt, dest);
 		}
 		else
 		{
-#ifdef INDEXSCAN_PATCH
+			Plan	   *plan;
+			int			j;
 
-			/*
-			 * Print moved in pg_parse_and_plan.	DZ - 27-8-1996
-			 */
-#else
-			/* ----------------
-			 *	print plan if debugging
-			 * ----------------
-			 */
-			if (DebugPrintPlan || DebugPPrintPlan)
+			/* If aborted transaction, quit now */
+			if (IsAbortedTransactionBlockState())
 			{
-				if (DebugPPrintPlan)
-				{
-					TPRINTF(TRACE_PRETTY_PLAN, "plan:");
-					nodeDisplay(plan);
-				}
-				else
-				{
-					TPRINTF(TRACE_PLAN, "plan:");
-					printf("\n%s\n\n", nodeToString(plan));
-				}
+				/* ----------------
+				 *	 the EndCommand() stuff is to tell the frontend
+				 *	 that the command ended. -cim 6/1/90
+				 * ----------------
+				 */
+				char	   *tag = "*ABORT STATE*";
+
+				elog(NOTICE, "current transaction is aborted, "
+					 "queries ignored until end of transaction block");
+
+				EndCommand(tag, dest);
+
+				break;
 			}
-#endif
 
+			plan = pg_plan_query(querytree);
+
+			/* if we got a cancel signal whilst planning, quit */
+			if (QueryCancel)
+				CancelQuery();
+
+			/* Initialize snapshot state for query */
 			SetQuerySnapshot();
 
 			/*
@@ -1505,7 +1462,7 @@ PostgresMain(int argc, char *argv[], int real_argc, char *real_argv[])
 	if (!IsUnderPostmaster)
 	{
 		puts("\nPOSTGRES backend interactive interface ");
-		puts("$Revision: 1.148 $ $Date: 2000/03/23 23:16:48 $\n");
+		puts("$Revision: 1.149 $ $Date: 2000/04/04 21:44:39 $\n");
 	}
 
 	/*