Reset per-tuple memory context between every row in a scan node, even when

there's no quals or projections. Currently this only matters for foreign
scans, as none of the other scan nodes litter the per-tuple memory context
when there's no quals or projections.

Author: hlinnaka

src/backend/executor/execScan.c

@@ -120,13 +120,17 @@ ExecScan(ScanState *node,
 	 */
 	qual = node->ps.qual;
 	projInfo = node->ps.ps_ProjInfo;
+	econtext = node->ps.ps_ExprContext;
 
 	/*
 	 * If we have neither a qual to check nor a projection to do, just skip
 	 * all the overhead and return the raw scan tuple.
 	 */
 	if (!qual && !projInfo)
+	{
+		ResetExprContext(econtext);
 		return ExecScanFetch(node, accessMtd, recheckMtd);
+	}
 
 	/*
 	 * Check to see if we're still projecting out tuples from a previous scan
@@ -148,7 +152,6 @@ ExecScan(ScanState *node,
 	 * storage allocated in the previous tuple cycle.  Note this can't happen
 	 * until we're done projecting out tuples from a scan tuple.
 	 */
-	econtext = node->ps.ps_ExprContext;
 	ResetExprContext(econtext);
 
 	/*