Restructure command destination handling so that we pass around

DestReceiver pointers instead of just CommandDest values.  The DestReceiver
is made at the point where the destination is selected, rather than
deep inside the executor.  This cleans up the original kluge implementation
of tstoreReceiver.c, and makes it easy to support retrieving results
from utility statements inside portals.  Thus, you can now do fun things
like Bind and Execute a FETCH or EXPLAIN command, and it'll all work
as expected (e.g., you can Describe the portal, or use Execute's count
parameter to suspend the output partway through).  Implementation involves
stuffing the utility command's output into a Tuplestore, which would be
kind of annoying for huge output sets, but should be quite acceptable
for typical uses of utility commands.

1 files changed, 20 insertions, 10 deletions

diff --git a/src/backend/commands/explain.c b/src/backend/commands/explain.c
index 2504d69fd06..28a6e0378c8 100644
--- a/src/backend/commands/explain.c
+++ b/src/backend/commands/explain.c
@@ -7,7 +7,7 @@
  * Portions Copyright (c) 1994-5, Regents of the University of California
  *
  * IDENTIFICATION
- *	  $Header: /cvsroot/pgsql/src/backend/commands/explain.c,v 1.107 2003/05/06 00:20:31 tgl Exp $
+ *	  $Header: /cvsroot/pgsql/src/backend/commands/explain.c,v 1.108 2003/05/06 20:26:26 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -67,21 +67,15 @@ static Node *make_ors_ands_explicit(List *orclauses);
  *	  execute an EXPLAIN command
  */
 void
-ExplainQuery(ExplainStmt *stmt, CommandDest dest)
+ExplainQuery(ExplainStmt *stmt, DestReceiver *dest)
 {
 	Query	   *query = stmt->query;
 	TupOutputState *tstate;
-	TupleDesc	tupdesc;
 	List	   *rewritten;
 	List	   *l;
 
-	/* need a tuple descriptor representing a single TEXT column */
-	tupdesc = CreateTemplateTupleDesc(1, false);
-	TupleDescInitEntry(tupdesc, (AttrNumber) 1, "QUERY PLAN",
-					   TEXTOID, -1, 0, false);
-
 	/* prepare for projection of tuples */
-	tstate = begin_tup_output_tupdesc(dest, tupdesc);
+	tstate = begin_tup_output_tupdesc(dest, ExplainResultDesc(stmt));
 
 	if (query->commandType == CMD_UTILITY)
 	{
@@ -120,6 +114,22 @@ ExplainQuery(ExplainStmt *stmt, CommandDest dest)
 }
 
 /*
+ * ExplainResultDesc -
+ *	  construct the result tupledesc for an EXPLAIN
+ */
+TupleDesc
+ExplainResultDesc(ExplainStmt *stmt)
+{
+	TupleDesc	tupdesc;
+
+	/* need a tuple descriptor representing a single TEXT column */
+	tupdesc = CreateTemplateTupleDesc(1, false);
+	TupleDescInitEntry(tupdesc, (AttrNumber) 1, "QUERY PLAN",
+					   TEXTOID, -1, 0, false);
+	return tupdesc;
+}
+
+/*
  * ExplainOneQuery -
  *	  print out the execution plan for one query
  */
@@ -169,7 +179,7 @@ ExplainOneQuery(Query *query, ExplainStmt *stmt, TupOutputState *tstate)
 	plan = planner(query, isCursor, cursorOptions);
 
 	/* Create a QueryDesc requesting no output */
-	queryDesc = CreateQueryDesc(query, plan, None, NULL, NULL,
+	queryDesc = CreateQueryDesc(query, plan, None_Receiver, NULL, NULL,
 								stmt->analyze);
 
 	ExplainOnePlan(queryDesc, stmt, tstate);