Implement SQL-standard WITH clauses, including WITH RECURSIVE.

There are some unimplemented aspects: recursive queries must use UNION ALL
(should allow UNION too), and we don't have SEARCH or CYCLE clauses.
These might or might not get done for 8.4, but even without them it's a
pretty useful feature.

There are also a couple of small loose ends and definitional quibbles,
which I'll send a memo about to pgsql-hackers shortly.  But let's land
the patch now so we can get on with other development.

Yoshiyuki Asaba, with lots of help from Tatsuo Ishii and Tom Lane

1 files changed, 91 insertions, 5 deletions

diff --git a/src/backend/utils/sort/tuplestore.c b/src/backend/utils/sort/tuplestore.c
index 3b53ad28a5..e127de34e5 100644
--- a/src/backend/utils/sort/tuplestore.c
+++ b/src/backend/utils/sort/tuplestore.c
@@ -46,7 +46,7 @@
  * Portions Copyright (c) 1994, Regents of the University of California
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/utils/sort/tuplestore.c,v 1.40 2008/10/01 19:51:49 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/backend/utils/sort/tuplestore.c,v 1.41 2008/10/04 21:56:54 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -86,7 +86,7 @@ typedef enum
 typedef struct
 {
 	int			eflags;			/* capability flags */
-	bool		eof_reached;	/* read reached EOF */
+	bool		eof_reached;	/* read has reached EOF */
 	int			current;		/* next array index to read */
 	int			file;			/* temp file# */
 	off_t		offset;			/* byte offset in file */
@@ -374,6 +374,39 @@ tuplestore_alloc_read_pointer(Tuplestorestate *state, int eflags)
 }
 
 /*
+ * tuplestore_clear
+ *
+ *	Delete all the contents of a tuplestore, and reset its read pointers
+ *	to the start.
+ */
+void
+tuplestore_clear(Tuplestorestate *state)
+{
+	int			i;
+	TSReadPointer *readptr;
+
+	if (state->myfile)
+		BufFileClose(state->myfile);
+	state->myfile = NULL;
+	if (state->memtuples)
+	{
+		for (i = 0; i < state->memtupcount; i++)
+		{
+			FREEMEM(state, GetMemoryChunkSpace(state->memtuples[i]));
+			pfree(state->memtuples[i]);
+		}
+	}
+	state->status = TSS_INMEM;
+	state->memtupcount = 0;
+	readptr = state->readptrs;
+	for (i = 0; i < state->readptrcount; readptr++, i++)
+	{
+		readptr->eof_reached = false;
+		readptr->current = 0;
+	}
+}
+
+/*
  * tuplestore_end
  *
  *	Release resources and clean up.
@@ -463,9 +496,13 @@ tuplestore_ateof(Tuplestorestate *state)
  *
  * Note that the input tuple is always copied; the caller need not save it.
  *
- * Any read pointer that is currently "AT EOF" remains so (the read pointer
- * implicitly advances along with the write pointer); otherwise the read
- * pointer is unchanged.  This is for the convenience of nodeMaterial.c.
+ * If the active read pointer is currently "at EOF", it remains so (the read
+ * pointer implicitly advances along with the write pointer); otherwise the
+ * read pointer is unchanged.  Non-active read pointers do not move, which
+ * means they are certain to not be "at EOF" immediately after puttuple.
+ * This curious-seeming behavior is for the convenience of nodeMaterial.c and
+ * nodeCtescan.c, which would otherwise need to do extra pointer repositioning
+ * steps.
  *
  * tuplestore_puttupleslot() is a convenience routine to collect data from
  * a TupleTableSlot without an extra copy operation.
@@ -519,11 +556,27 @@ tuplestore_putvalues(Tuplestorestate *state, TupleDesc tdesc,
 static void
 tuplestore_puttuple_common(Tuplestorestate *state, void *tuple)
 {
+	TSReadPointer *readptr;
+	int			i;
+
 	switch (state->status)
 	{
 		case TSS_INMEM:
 
 			/*
+			 * Update read pointers as needed; see API spec above.
+			 */
+			readptr = state->readptrs;
+			for (i = 0; i < state->readptrcount; readptr++, i++)
+			{
+				if (readptr->eof_reached && i != state->activeptr)
+				{
+					readptr->eof_reached = false;
+					readptr->current = state->memtupcount;
+				}
+			}
+
+			/*
 			 * Grow the array as needed.  Note that we try to grow the array
 			 * when there is still one free slot remaining --- if we fail,
 			 * there'll still be room to store the incoming tuple, and then
@@ -572,6 +625,24 @@ tuplestore_puttuple_common(Tuplestorestate *state, void *tuple)
 			dumptuples(state);
 			break;
 		case TSS_WRITEFILE:
+
+			/*
+			 * Update read pointers as needed; see API spec above.
+			 * Note: BufFileTell is quite cheap, so not worth trying
+			 * to avoid multiple calls.
+			 */
+			readptr = state->readptrs;
+			for (i = 0; i < state->readptrcount; readptr++, i++)
+			{
+				if (readptr->eof_reached && i != state->activeptr)
+				{
+					readptr->eof_reached = false;
+					BufFileTell(state->myfile,
+								&readptr->file,
+								&readptr->offset);
+				}
+			}
+
 			WRITETUP(state, tuple);
 			break;
 		case TSS_READFILE:
@@ -588,6 +659,21 @@ tuplestore_puttuple_common(Tuplestorestate *state, void *tuple)
 							SEEK_SET) != 0)
 				elog(ERROR, "tuplestore seek to EOF failed");
 			state->status = TSS_WRITEFILE;
+
+			/*
+			 * Update read pointers as needed; see API spec above.
+			 */
+			readptr = state->readptrs;
+			for (i = 0; i < state->readptrcount; readptr++, i++)
+			{
+				if (readptr->eof_reached && i != state->activeptr)
+				{
+					readptr->eof_reached = false;
+					readptr->file = state->writepos_file;
+					readptr->offset = state->writepos_offset;
+				}
+			}
+
 			WRITETUP(state, tuple);
 			break;
 		default: