Restructure parsetree representation of DECLARE CURSOR: now it's a

utility statement (DeclareCursorStmt) with a SELECT query dangling from
it, rather than a SELECT query with a few unusual fields in it.  Add
code to determine whether a planned query can safely be run backwards.
If DECLARE CURSOR specifies SCROLL, ensure that the plan can be run
backwards by adding a Materialize plan node if it can't.  Without SCROLL,
you get an error if you try to fetch backwards from a cursor that can't
handle it.  (There is still some discussion about what the exact
behavior should be, but this is necessary infrastructure in any case.)
Along the way, make EXPLAIN DECLARE CURSOR work.

1 files changed, 34 insertions, 56 deletions

diff --git a/src/backend/parser/analyze.c b/src/backend/parser/analyze.c
index 2089008bbf5..3486a1e010b 100644
--- a/src/backend/parser/analyze.c
+++ b/src/backend/parser/analyze.c
@@ -6,7 +6,7 @@
  * Portions Copyright (c) 1996-2002, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- *	$Header: /cvsroot/pgsql/src/backend/parser/analyze.c,v 1.264 2003/02/13 22:50:01 tgl Exp $
+ *	$Header: /cvsroot/pgsql/src/backend/parser/analyze.c,v 1.265 2003/03/10 03:53:50 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -96,6 +96,8 @@ static Query *transformSelectStmt(ParseState *pstate, SelectStmt *stmt);
 static Query *transformSetOperationStmt(ParseState *pstate, SelectStmt *stmt);
 static Node *transformSetOperationTree(ParseState *pstate, SelectStmt *stmt);
 static Query *transformUpdateStmt(ParseState *pstate, UpdateStmt *stmt);
+static Query *transformDeclareCursorStmt(ParseState *pstate,
+										 DeclareCursorStmt *stmt);
 static Query *transformPrepareStmt(ParseState *pstate, PrepareStmt *stmt);
 static Query *transformExecuteStmt(ParseState *pstate, ExecuteStmt *stmt);
 static Query *transformCreateStmt(ParseState *pstate, CreateStmt *stmt,
@@ -313,6 +315,11 @@ transformStmt(ParseState *pstate, Node *parseTree,
 											   (SelectStmt *) parseTree);
 			break;
 
+		case T_DeclareCursorStmt:
+			result = transformDeclareCursorStmt(pstate,
+												(DeclareCursorStmt *) parseTree);
+			break;
+
 		default:
 
 			/*
@@ -445,7 +452,7 @@ transformInsertStmt(ParseState *pstate, InsertStmt *stmt,
 
 		Assert(IsA(selectQuery, Query));
 		Assert(selectQuery->commandType == CMD_SELECT);
-		if (selectQuery->into || selectQuery->isPortal)
+		if (selectQuery->into)
 			elog(ERROR, "INSERT ... SELECT may not specify INTO");
 
 		/*
@@ -1616,27 +1623,6 @@ transformSelectStmt(ParseState *pstate, SelectStmt *stmt)
 
 	qry->commandType = CMD_SELECT;
 
-	if (stmt->portalname)
-	{
-		/* DECLARE CURSOR */
-		if (stmt->into)
-			elog(ERROR, "DECLARE CURSOR must not specify INTO");
-		if (stmt->forUpdate)
-			elog(ERROR, "DECLARE/UPDATE is not supported"
-				 "\n\tCursors must be READ ONLY");
-		qry->into = makeNode(RangeVar);
-		qry->into->relname = stmt->portalname;
-		qry->isPortal = TRUE;
-		qry->isBinary = stmt->binary;	/* internal portal */
-	}
-	else
-	{
-		/* SELECT */
-		qry->into = stmt->into;
-		qry->isPortal = FALSE;
-		qry->isBinary = FALSE;
-	}
-
 	/* make FOR UPDATE clause available to addRangeTableEntry */
 	pstate->p_forUpdate = stmt->forUpdate;
 
@@ -1646,6 +1632,8 @@ transformSelectStmt(ParseState *pstate, SelectStmt *stmt)
 	/* transform targetlist */
 	qry->targetList = transformTargetList(pstate, stmt->targetList);
 
+	/* handle any SELECT INTO/CREATE TABLE AS spec */
+	qry->into = stmt->into;
 	if (stmt->intoColNames)
 		applyColumnNames(qry->targetList, stmt->intoColNames);
 
@@ -1708,8 +1696,6 @@ transformSetOperationStmt(ParseState *pstate, SelectStmt *stmt)
 	SetOperationStmt *sostmt;
 	RangeVar   *into;
 	List	   *intoColNames;
-	char	   *portalname;
-	bool		binary;
 	List	   *sortClause;
 	Node	   *limitOffset;
 	Node	   *limitCount;
@@ -1738,14 +1724,10 @@ transformSetOperationStmt(ParseState *pstate, SelectStmt *stmt)
 		   leftmostSelect->larg == NULL);
 	into = leftmostSelect->into;
 	intoColNames = leftmostSelect->intoColNames;
-	portalname = stmt->portalname;
-	binary = stmt->binary;
 
 	/* clear them to prevent complaints in transformSetOperationTree() */
 	leftmostSelect->into = NULL;
 	leftmostSelect->intoColNames = NIL;
-	stmt->portalname = NULL;
-	stmt->binary = false;
 
 	/*
 	 * These are not one-time, exactly, but we want to process them here
@@ -1825,36 +1807,13 @@ transformSetOperationStmt(ParseState *pstate, SelectStmt *stmt)
 	}
 
 	/*
-	 * Insert one-time items into top-level query
+	 * Handle SELECT INTO/CREATE TABLE AS.
 	 *
-	 * This needs to agree with transformSelectStmt!
-	 */
-	if (portalname)
-	{
-		/* DECLARE CURSOR */
-		if (into)
-			elog(ERROR, "DECLARE CURSOR must not specify INTO");
-		if (forUpdate)
-			elog(ERROR, "DECLARE/UPDATE is not supported"
-				 "\n\tCursors must be READ ONLY");
-		qry->into = makeNode(RangeVar);
-		qry->into->relname = portalname;
-		qry->isPortal = TRUE;
-		qry->isBinary = binary; /* internal portal */
-	}
-	else
-	{
-		/* SELECT */
-		qry->into = into;
-		qry->isPortal = FALSE;
-		qry->isBinary = FALSE;
-	}
-
-	/*
 	 * Any column names from CREATE TABLE AS need to be attached to both
 	 * the top level and the leftmost subquery.  We do not do this earlier
 	 * because we do *not* want the targetnames list to be affected.
 	 */
+	qry->into = into;
 	if (intoColNames)
 	{
 		applyColumnNames(qry->targetList, intoColNames);
@@ -1938,8 +1897,6 @@ transformSetOperationTree(ParseState *pstate, SelectStmt *stmt)
 	 */
 	if (stmt->into)
 		elog(ERROR, "INTO is only allowed on first SELECT of UNION/INTERSECT/EXCEPT");
-	if (stmt->portalname)		/* should not happen */
-		elog(ERROR, "Portal may not appear in UNION/INTERSECT/EXCEPT");
 	/* We don't support forUpdate with set ops at the moment. */
 	if (stmt->forUpdate)
 		elog(ERROR, "SELECT FOR UPDATE is not allowed with UNION/INTERSECT/EXCEPT");
@@ -2328,6 +2285,27 @@ transformAlterTableStmt(ParseState *pstate, AlterTableStmt *stmt,
 }
 
 static Query *
+transformDeclareCursorStmt(ParseState *pstate, DeclareCursorStmt *stmt)
+{
+	Query	   *result = makeNode(Query);
+	List	   *extras_before = NIL,
+			   *extras_after = NIL;
+
+	result->commandType = CMD_UTILITY;
+	result->utilityStmt = (Node *) stmt;
+
+	stmt->query = (Node *) transformStmt(pstate, stmt->query,
+										 &extras_before, &extras_after);
+
+	/* Shouldn't get any extras, since grammar only allows SelectStmt */
+	if (extras_before || extras_after)
+		elog(ERROR, "transformDeclareCursorStmt: internal error");
+
+	return result;
+}
+
+
+static Query *
 transformPrepareStmt(ParseState *pstate, PrepareStmt *stmt)
 {
 	Query	   *result = makeNode(Query);