refactor-portal-start.patch

diff --git a/src/backend/commands/portalcmds.c b/src/backend/commands/portalcmds.c
index 89086aa..497657e 100644
--- a/src/backend/commands/portalcmds.c
+++ b/src/backend/commands/portalcmds.c
@@ -121,7 +121,7 @@ PerformCursorOpen(PlannedStmt *stmt, ParamListInfo params,
 	/*
 	 * Start execution, inserting parameters if any.
 	 */
-	PortalStart(portal, params, GetActiveSnapshot());
+	PortalStart(portal, params, true);
 
 	Assert(portal->strategy == PORTAL_ONE_SELECT);
 
diff --git a/src/backend/commands/prepare.c b/src/backend/commands/prepare.c
index a949215..dd0e837 100644
--- a/src/backend/commands/prepare.c
+++ b/src/backend/commands/prepare.c
@@ -278,7 +278,7 @@ ExecuteQuery(ExecuteStmt *stmt, const char *queryString,
 	/*
 	 * Run the portal to completion.
 	 */
-	PortalStart(portal, paramLI, GetActiveSnapshot());
+	PortalStart(portal, paramLI, true);
 
 	(void) PortalRun(portal, FETCH_ALL, false, dest, dest, completionTag);
 
diff --git a/src/backend/executor/spi.c b/src/backend/executor/spi.c
index 688279c..7af3abf 100644
--- a/src/backend/executor/spi.c
+++ b/src/backend/executor/spi.c
@@ -1126,7 +1126,6 @@ SPI_cursor_open_internal(const char *name, SPIPlanPtr plan,
 	CachedPlan *cplan;
 	List	   *stmt_list;
 	char	   *query_string;
-	Snapshot	snapshot;
 	MemoryContext oldcontext;
 	Portal		portal;
 
@@ -1269,15 +1268,6 @@ SPI_cursor_open_internal(const char *name, SPIPlanPtr plan,
 		}
 	}
 
-	/* Set up the snapshot to use. */
-	if (read_only)
-		snapshot = GetActiveSnapshot();
-	else
-	{
-		CommandCounterIncrement();
-		snapshot = GetTransactionSnapshot();
-	}
-
 	/*
 	 * If the plan has parameters, copy them into the portal.  Note that this
 	 * must be done after revalidating the plan, because in dynamic parameter
@@ -1293,7 +1283,13 @@ SPI_cursor_open_internal(const char *name, SPIPlanPtr plan,
 	/*
 	 * Start portal execution.
 	 */
-	PortalStart(portal, paramLI, snapshot);
+	if (read_only)
+		PortalStart(portal, paramLI, true);
+	else
+	{
+		CommandCounterIncrement();
+		PortalStart(portal, paramLI, false);
+	}
 
 	Assert(portal->strategy != PORTAL_MULTI_QUERY);
 
diff --git a/src/backend/tcop/postgres.c b/src/backend/tcop/postgres.c
index 976a832..a5484d9 100644
--- a/src/backend/tcop/postgres.c
+++ b/src/backend/tcop/postgres.c
@@ -973,7 +973,7 @@ exec_simple_query(const char *query_string)
 		/*
 		 * Start the portal.  No parameters here.
 		 */
-		PortalStart(portal, NULL, InvalidSnapshot);
+		PortalStart(portal, NULL, false);
 
 		/*
 		 * Select the appropriate output format: text unless we are doing a
@@ -1703,7 +1703,7 @@ exec_bind_message(StringInfo input_message)
 	/*
 	 * And we're ready to start portal execution.
 	 */
-	PortalStart(portal, params, InvalidSnapshot);
+	PortalStart(portal, params, false);
 
 	/*
 	 * Apply the result format requests to the portal.
diff --git a/src/backend/tcop/pquery.c b/src/backend/tcop/pquery.c
index 466727b..c41272b 100644
--- a/src/backend/tcop/pquery.c
+++ b/src/backend/tcop/pquery.c
@@ -455,7 +455,7 @@ FetchStatementTargetList(Node *stmt)
  * tupdesc (if any) is known.
  */
 void
-PortalStart(Portal portal, ParamListInfo params, Snapshot snapshot)
+PortalStart(Portal portal, ParamListInfo params, bool use_active_snapshot)
 {
 	Portal		saveActivePortal;
 	ResourceOwner saveResourceOwner;
@@ -497,8 +497,8 @@ PortalStart(Portal portal, ParamListInfo params, Snapshot snapshot)
 			case PORTAL_ONE_SELECT:
 
 				/* Must set snapshot before starting executor. */
-				if (snapshot)
-					PushActiveSnapshot(snapshot);
+				if (use_active_snapshot)
+					PushActiveSnapshot(GetActiveSnapshot());
 				else
 					PushActiveSnapshot(GetTransactionSnapshot());
 
diff --git a/src/include/tcop/pquery.h b/src/include/tcop/pquery.h
index 2a5e871..ce37af3 100644
--- a/src/include/tcop/pquery.h
+++ b/src/include/tcop/pquery.h
@@ -28,7 +28,7 @@ extern List *FetchPortalTargetList(Portal portal);
 extern List *FetchStatementTargetList(Node *stmt);
 
 extern void PortalStart(Portal portal, ParamListInfo params,
-			Snapshot snapshot);
+			bool use_active_snapshot);
 
 extern void PortalSetResultFormat(Portal portal, int nFormats,
 					  int16 *formats);