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, 6 insertions, 95 deletions

diff --git a/src/backend/tcop/pquery.c b/src/backend/tcop/pquery.c
index 1e02e42193d..29d5018440d 100644
--- a/src/backend/tcop/pquery.c
+++ b/src/backend/tcop/pquery.c
@@ -8,19 +8,15 @@
  *
  *
  * IDENTIFICATION
- *	  $Header: /cvsroot/pgsql/src/backend/tcop/pquery.c,v 1.58 2002/12/15 16:17:52 tgl Exp $
+ *	  $Header: /cvsroot/pgsql/src/backend/tcop/pquery.c,v 1.59 2003/03/10 03:53:51 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
 
 #include "postgres.h"
 
-#include "commands/portalcmds.h"
-#include "executor/execdefs.h"
 #include "executor/executor.h"
 #include "tcop/pquery.h"
-#include "utils/memutils.h"
-#include "utils/ps_status.h"
 
 
 /*
@@ -64,38 +60,6 @@ FreeQueryDesc(QueryDesc *qdesc)
 	pfree(qdesc);
 }
 
-/* ----------------
- *		PreparePortal
- * ----------------
- */
-Portal
-PreparePortal(char *portalName)
-{
-	Portal		portal;
-
-	/*
-	 * Check for already-in-use portal name.
-	 */
-	portal = GetPortalByName(portalName);
-	if (PortalIsValid(portal))
-	{
-		/*
-		 * XXX Should we raise an error rather than closing the old
-		 * portal?
-		 */
-		elog(WARNING, "Closing pre-existing portal \"%s\"",
-			 portalName);
-		PortalDrop(portal);
-	}
-
-	/*
-	 * Create the new portal.
-	 */
-	portal = CreatePortal(portalName);
-
-	return portal;
-}
-
 
 /*
  * ProcessQuery
@@ -116,10 +80,6 @@ ProcessQuery(Query *parsetree,
 			 char *completionTag)
 {
 	int			operation = parsetree->commandType;
-	bool		isRetrieveIntoPortal = false;
-	char	   *intoName = NULL;
-	Portal		portal = NULL;
-	MemoryContext oldContext = NULL;
 	QueryDesc  *queryDesc;
 
 	/*
@@ -127,16 +87,7 @@ ProcessQuery(Query *parsetree,
 	 */
 	if (operation == CMD_SELECT)
 	{
-		if (parsetree->isPortal)
-		{
-			isRetrieveIntoPortal = true;
-			/* If binary portal, switch to alternate output format */
-			if (dest == Remote && parsetree->isBinary)
-				dest = RemoteInternal;
-			/* Check for invalid context (must be in transaction block) */
-			RequireTransactionChain((void *) parsetree, "DECLARE CURSOR");
-		}
-		else if (parsetree->into != NULL)
+		if (parsetree->into != NULL)
 		{
 			/*
 			 * SELECT INTO table (a/k/a CREATE AS ... SELECT).
@@ -150,57 +101,17 @@ ProcessQuery(Query *parsetree,
 	}
 
 	/*
-	 * If retrieving into a portal, set up the portal and copy the
-	 * parsetree and plan into its memory context.
+	 * Create the QueryDesc object
 	 */
-	if (isRetrieveIntoPortal)
-	{
-		intoName = parsetree->into->relname;
-		portal = PreparePortal(intoName);
-		oldContext = MemoryContextSwitchTo(PortalGetHeapMemory(portal));
-		parsetree = copyObject(parsetree);
-		plan = copyObject(plan);
-		intoName = parsetree->into->relname;	/* use copied name in
-												 * QueryDesc */
-
-		/*
-		 * We stay in portal's memory context for now, so that query desc
-		 * is also allocated in the portal context.
-		 */
-	}
+	queryDesc = CreateQueryDesc(parsetree, plan, dest, NULL, NULL, false);
 
 	/*
-	 * Now we can create the QueryDesc object.
-	 */
-	queryDesc = CreateQueryDesc(parsetree, plan, dest, intoName, NULL, false);
-
-	/*
-	 * call ExecStart to prepare the plan for execution
+	 * Call ExecStart to prepare the plan for execution
 	 */
 	ExecutorStart(queryDesc);
 
 	/*
-	 * If retrieve into portal, stop now; we do not run the plan until a
-	 * FETCH command is received.
-	 */
-	if (isRetrieveIntoPortal)
-	{
-		/* Arrange to shut down the executor if portal is dropped */
-		PortalSetQuery(portal, queryDesc, PortalCleanup);
-
-		/* Now we can return to caller's memory context. */
-		MemoryContextSwitchTo(oldContext);
-
-		/* Set completion tag.	SQL calls this operation DECLARE CURSOR */
-		if (completionTag)
-			strcpy(completionTag, "DECLARE CURSOR");
-
-		return;
-	}
-
-	/*
-	 * Now we get to the important call to ExecutorRun() where we actually
-	 * run the plan..
+	 * And run the plan.
 	 */
 	ExecutorRun(queryDesc, ForwardScanDirection, 0L);