Fix coredump problem in plpgsql's RETURN NEXT. When a SELECT INTO

that's selecting into a RECORD variable returns zero rows, make it
assign an all-nulls row to the RECORD; this is consistent with what
happens when the SELECT INTO target is not a RECORD.  In support of
this, tweak the SPI code so that a valid tuple descriptor is returned
even when a SPI select returns no rows.

doc/src/sgml/spi.sgml

 <!--
-$Header: /cvsroot/pgsql/doc/src/sgml/spi.sgml,v 1.24 2002/12/30 22:10:53 tgl Exp $
+$Header: /cvsroot/pgsql/doc/src/sgml/spi.sgml,v 1.25 2003/01/21 22:06:11 tgl Exp $
 -->
 
 <Chapter id="spi">
@@ -476,7 +476,7 @@ You may pass multiple queries in one string or query string may be
    The actual number of tuples for which the (last) query was executed is
    returned in the global variable SPI_processed (if not <ReturnValue>SPI_OK_UTILITY</ReturnValue>).
 
-   If <ReturnValue>SPI_OK_SELECT</ReturnValue> is returned and SPI_processed &gt; 0 then you may use global
+   If <ReturnValue>SPI_OK_SELECT</ReturnValue> is returned then you may use global
    pointer SPITupleTable *SPI_tuptable to access the result tuples.
 </Para>
 
@@ -517,7 +517,7 @@ You may pass multiple queries in one string or query string may be
 <TITLE>Structures
 </TITLE>
 <Para>
-   If <ReturnValue>SPI_OK_SELECT</ReturnValue> is returned and SPI_processed &gt; 0 then you may use the global
+   If <ReturnValue>SPI_OK_SELECT</ReturnValue> is returned then you may use the global
    pointer SPITupleTable *SPI_tuptable to access the selected tuples.
 </Para>
 

src/backend/executor/spi.c

@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $Header: /cvsroot/pgsql/src/backend/executor/spi.c,v 1.83 2002/12/30 22:10:54 tgl Exp $
+ *	  $Header: /cvsroot/pgsql/src/backend/executor/spi.c,v 1.84 2003/01/21 22:06:12 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -874,13 +874,13 @@ SPI_cursor_close(Portal portal)
 /* =================== private functions =================== */
 
 /*
- * spi_printtup
- *		store tuple retrieved by Executor into SPITupleTable
+ * spi_dest_setup
+ *		Initialize to receive tuples from Executor into SPITupleTable
  *		of current SPI procedure
- *
  */
 void
-spi_printtup(HeapTuple tuple, TupleDesc tupdesc, DestReceiver *self)
+spi_dest_setup(DestReceiver *self, int operation,
+			   const char *portalName, TupleDesc typeinfo)
 {
 	SPITupleTable *tuptable;
 	MemoryContext oldcxt;
@@ -891,15 +891,15 @@ spi_printtup(HeapTuple tuple, TupleDesc tupdesc, DestReceiver *self)
 	 * _SPI_connected
 	 */
 	if (_SPI_curid != _SPI_connected || _SPI_connected < 0)
-		elog(FATAL, "SPI: improper call to spi_printtup");
+		elog(FATAL, "SPI: improper call to spi_dest_setup");
 	if (_SPI_current != &(_SPI_stack[_SPI_curid]))
-		elog(FATAL, "SPI: stack corrupted in spi_printtup");
+		elog(FATAL, "SPI: stack corrupted in spi_dest_setup");
+
+	if (_SPI_current->tuptable != NULL)
+		elog(FATAL, "SPI: improper call to spi_dest_setup");
 
 	oldcxt = _SPI_procmem();	/* switch to procedure memory context */
 
-	tuptable = _SPI_current->tuptable;
-	if (tuptable == NULL)
-	{
 	tuptabcxt = AllocSetContextCreate(CurrentMemoryContext,
 									  "SPI TupTable",
 									  ALLOCSET_DEFAULT_MINSIZE,
@@ -912,11 +912,36 @@ spi_printtup(HeapTuple tuple, TupleDesc tupdesc, DestReceiver *self)
 	tuptable->tuptabcxt = tuptabcxt;
 	tuptable->alloced = tuptable->free = 128;
 	tuptable->vals = (HeapTuple *) palloc(tuptable->alloced * sizeof(HeapTuple));
-		tuptable->tupdesc = CreateTupleDescCopy(tupdesc);
-	}
-	else
-	{
-		MemoryContextSwitchTo(tuptable->tuptabcxt);
+	tuptable->tupdesc = CreateTupleDescCopy(typeinfo);
+
+	MemoryContextSwitchTo(oldcxt);
+}
+
+/*
+ * spi_printtup
+ *		store tuple retrieved by Executor into SPITupleTable
+ *		of current SPI procedure
+ */
+void
+spi_printtup(HeapTuple tuple, TupleDesc tupdesc, DestReceiver *self)
+{
+	SPITupleTable *tuptable;
+	MemoryContext oldcxt;
+
+	/*
+	 * When called by Executor _SPI_curid expected to be equal to
+	 * _SPI_connected
+	 */
+	if (_SPI_curid != _SPI_connected || _SPI_connected < 0)
+		elog(FATAL, "SPI: improper call to spi_printtup");
+	if (_SPI_current != &(_SPI_stack[_SPI_curid]))
+		elog(FATAL, "SPI: stack corrupted in spi_printtup");
+
+	tuptable = _SPI_current->tuptable;
+	if (tuptable == NULL)
+		elog(FATAL, "SPI: improper call to spi_printtup");
+
+	oldcxt = MemoryContextSwitchTo(tuptable->tuptabcxt);
 
 	if (tuptable->free == 0)
 	{
@@ -925,13 +950,11 @@ spi_printtup(HeapTuple tuple, TupleDesc tupdesc, DestReceiver *self)
 		tuptable->vals = (HeapTuple *) repalloc(tuptable->vals,
 								  tuptable->alloced * sizeof(HeapTuple));
 	}
-	}
 
 	tuptable->vals[tuptable->alloced - tuptable->free] = heap_copytuple(tuple);
 	(tuptable->free)--;
 
 	MemoryContextSwitchTo(oldcxt);
-	return;
 }
 
 /*
@@ -1448,19 +1471,10 @@ _SPI_checktuples(void)
 	SPITupleTable *tuptable = _SPI_current->tuptable;
 	bool		failed = false;
 
-	if (processed == 0)
-	{
-		if (tuptable != NULL)
-			failed = true;
-	}
-	else
-	{
-		/* some tuples were processed */
-		if (tuptable == NULL)	/* spi_printtup was not called */
+	if (tuptable == NULL)	/* spi_dest_setup was not called */
 		failed = true;
 	else if (processed != (tuptable->alloced - tuptable->free))
 		failed = true;
-	}
 
 	return failed;
 }

src/backend/tcop/dest.c

@@ -8,7 +8,7 @@
  * Portions Copyright (c) 1994, Regents of the University of California
  *
  * IDENTIFICATION
- *	  $Header: /cvsroot/pgsql/src/backend/tcop/dest.c,v 1.49 2002/06/20 20:29:36 momjian Exp $
+ *	  $Header: /cvsroot/pgsql/src/backend/tcop/dest.c,v 1.50 2003/01/21 22:06:12 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -64,7 +64,7 @@ static DestReceiver debugtupDR = {
 	debugtup, debugSetup, donothingCleanup
 };
 static DestReceiver spi_printtupDR = {
-	spi_printtup, donothingSetup, donothingCleanup
+	spi_printtup, spi_dest_setup, donothingCleanup
 };
 
 /* ----------------

src/include/access/printtup.h

@@ -7,7 +7,7 @@
  * Portions Copyright (c) 1996-2002, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $Id: printtup.h,v 1.22 2002/09/04 20:31:37 momjian Exp $
+ * $Id: printtup.h,v 1.23 2003/01/21 22:06:12 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -23,7 +23,9 @@ extern void debugSetup(DestReceiver *self, int operation,
 extern void debugtup(HeapTuple tuple, TupleDesc typeinfo,
 		 DestReceiver *self);
 
-/* XXX this one is really in executor/spi.c */
+/* XXX these are really in executor/spi.c */
+extern void spi_dest_setup(DestReceiver *self, int operation,
+		   const char *portalName, TupleDesc typeinfo);
 extern void spi_printtup(HeapTuple tuple, TupleDesc tupdesc,
 			 DestReceiver *self);
 

src/pl/plpgsql/src/pl_exec.c

@@ -3,7 +3,7 @@
  *			  procedural language
  *
  * IDENTIFICATION
- *	  $Header: /cvsroot/pgsql/src/pl/plpgsql/src/pl_exec.c,v 1.76 2002/12/17 15:45:01 tgl Exp $
+ *	  $Header: /cvsroot/pgsql/src/pl/plpgsql/src/pl_exec.c,v 1.77 2003/01/21 22:06:12 tgl Exp $
  *
  *	  This software is copyrighted by Jan Wieck - Hamburg.
  *
@@ -1356,15 +1356,15 @@ exec_stmt_fors(PLpgSQL_execstate * estate, PLpgSQL_stmt_fors * stmt)
 	exec_run_select(estate, stmt->query, 0, &portal);
 
 	SPI_cursor_fetch(portal, true, 10);
-	n = SPI_processed;
 	tuptab = SPI_tuptable;
+	n = SPI_processed;
 
 	/*
 	 * If the query didn't return any rows, set the target to NULL and
 	 * return with FOUND = false.
 	 */
 	if (n == 0)
-		exec_move_row(estate, rec, row, NULL, NULL);
+		exec_move_row(estate, rec, row, NULL, tuptab->tupdesc);
 	else
 		found = true;			/* processed at least one tuple */
 
@@ -1478,6 +1478,7 @@ exec_stmt_select(PLpgSQL_execstate * estate, PLpgSQL_stmt_select * stmt)
 	 * Run the query
 	 */
 	exec_run_select(estate, stmt->query, 1, NULL);
+	tuptab = estate->eval_tuptable;
 	n = estate->eval_processed;
 
 	/*
@@ -1486,7 +1487,7 @@ exec_stmt_select(PLpgSQL_execstate * estate, PLpgSQL_stmt_select * stmt)
 	 */
 	if (n == 0)
 	{
-		exec_move_row(estate, rec, row, NULL, NULL);
+		exec_move_row(estate, rec, row, NULL, tuptab->tupdesc);
 		exec_eval_cleanup(estate);
 		return PLPGSQL_RC_OK;
 	}
@@ -1494,7 +1495,6 @@ exec_stmt_select(PLpgSQL_execstate * estate, PLpgSQL_stmt_select * stmt)
 	/*
 	 * Put the result into the target and set found to true
 	 */
-	tuptab = estate->eval_tuptable;
 	exec_move_row(estate, rec, row, tuptab->vals[0], tuptab->tupdesc);
 	exec_set_found(estate, true);
 
@@ -1627,6 +1627,8 @@ exec_stmt_return_next(PLpgSQL_execstate * estate,
 	{
 		PLpgSQL_rec *rec = (PLpgSQL_rec *) (estate->datums[stmt->rec->recno]);
 
+		if (!HeapTupleIsValid(rec->tup))
+			elog(ERROR, "record \"%s\" is unassigned yet", rec->refname);
 		if (!compatible_tupdesc(tupdesc, rec->tupdesc))
 			elog(ERROR, "Wrong record type supplied in RETURN NEXT");
 		tuple = rec->tup;
@@ -2369,15 +2371,15 @@ exec_stmt_dynfors(PLpgSQL_execstate * estate, PLpgSQL_stmt_dynfors * stmt)
 	 * Fetch the initial 10 tuples
 	 */
 	SPI_cursor_fetch(portal, true, 10);
-	n = SPI_processed;
 	tuptab = SPI_tuptable;
+	n = SPI_processed;
 
 	/*
 	 * If the query didn't return any rows, set the target to NULL and
 	 * return with FOUND = false.
 	 */
 	if (n == 0)
-		exec_move_row(estate, rec, row, NULL, NULL);
+		exec_move_row(estate, rec, row, NULL, tuptab->tupdesc);
 	else
 		found = true;
 
@@ -2776,8 +2778,8 @@ exec_stmt_fetch(PLpgSQL_execstate * estate, PLpgSQL_stmt_fetch * stmt)
 	 * ----------
 	 */
 	SPI_cursor_fetch(portal, true, 1);
-	n = SPI_processed;
 	tuptab = SPI_tuptable;
+	n = SPI_processed;
 
 	/* ----------
 	 * If the FETCH didn't return a row, set the target
@@ -2786,7 +2788,7 @@ exec_stmt_fetch(PLpgSQL_execstate * estate, PLpgSQL_stmt_fetch * stmt)
 	 */
 	if (n == 0)
 	{
-		exec_move_row(estate, rec, row, NULL, NULL);
+		exec_move_row(estate, rec, row, NULL, tuptab->tupdesc);
 		return PLPGSQL_RC_OK;
 	}
 
@@ -3353,8 +3355,8 @@ exec_move_row(PLpgSQL_execstate * estate,
 			  HeapTuple tup, TupleDesc tupdesc)
 {
 	/*
-	 * Record is simple - just put the tuple and its descriptor into the
-	 * record
+	 * Record is simple - just copy the tuple and its descriptor into the
+	 * record variable
 	 */
 	if (rec != NULL)
 	{
@@ -3372,13 +3374,34 @@ exec_move_row(PLpgSQL_execstate * estate,
 		if (HeapTupleIsValid(tup))
 		{
 			rec->tup = heap_copytuple(tup);
-			rec->tupdesc = CreateTupleDescCopy(tupdesc);
 			rec->freetup = true;
-			rec->freetupdesc = true;
+		}
+		else if (tupdesc)
+		{
+			/* If we have a tupdesc but no data, form an all-nulls tuple */
+			char		*nulls;
+
+			/* +1 to avoid possible palloc(0) if no attributes */
+			nulls = (char *) palloc(tupdesc->natts * sizeof(char) + 1);
+			memset(nulls, 'n', tupdesc->natts * sizeof(char));
+
+			rec->tup = heap_formtuple(tupdesc, NULL, nulls);
+			rec->freetup = true;
+
+			pfree(nulls);
 		}
 		else
 		{
 			rec->tup = NULL;
+		}
+
+		if (tupdesc)
+		{
+			rec->tupdesc = CreateTupleDescCopy(tupdesc);
+			rec->freetupdesc = true;
+		}
+		else
+		{
 			rec->tupdesc = NULL;
 		}
 
@@ -3395,6 +3418,9 @@ exec_move_row(PLpgSQL_execstate * estate,
 	 * table, or it might have fewer if the table has had columns added by
 	 * ALTER TABLE. Ignore extra columns and assume NULL for missing
 	 * columns, the same as heap_getattr would do.
+	 *
+	 * If we have no tuple data at all, we'll assign NULL to all columns
+	 * of the row variable.
 	 */
 	if (row != NULL)
 	{