postgres.git / summary / log / commit / refs

commit    5567d12ce030781a4f749c9cd2034b95a3b64424
Author:   Andres Freund <andres@anarazel.de>
Date:     Sat Feb 09 08:35:57 2019 +0000
First released in: 12.0, 11.2

    Plug leak in BuildTupleHashTable by creating ExprContext in correct context.
    
    In bf6c614a2f2c5 I added a expr context to evaluate the grouping
    expression. Unfortunately the code I added initialized them while in
    the calling context, rather the table context.  Additionally, I used
    CreateExprContext() rather than CreateStandaloneExprContext(), which
    creates the econtext in the estate's query context.
    
    Fix that by using CreateStandaloneExprContext when in the table's
    tablecxt. As we rely on the memory being freed by a memory context
    reset that means that the econtext's shutdown callbacks aren't being
    called, but that seems ok as the expressions are tightly controlled
    due to ExecBuildGroupingEqual().
    
    Bug: #15592
    Reported-By: Dmitry Marakasov
    Author: Andres Freund
    Discussion: https://postgr.es/m/20190114222838.h6r3fuyxjxkykf6t@alap3.anarazel.de
    Backpatch: 11, where I broke this in bf6c614a2f2c5


 src/backend/executor/execGrouping.c | 12 +++++++++---
 1 file changed, 9 insertions(+), 3 deletions(-)

diff --git a/src/backend/executor/execGrouping.c b/src/backend/executor/execGrouping.c
index 4e7600e4ed6..7cf001518a1 100644
--- a/src/backend/executor/execGrouping.c
+++ b/src/backend/executor/execGrouping.c
@@ -212,11 +212,17 @@ BuildTupleHashTable(PlanState *parent,
 													&TTSOpsMinimalTuple, &TTSOpsMinimalTuple,
 													numCols,
 													keyColIdx, eqfuncoids,
-													parent);
+													NULL);
 
-	MemoryContextSwitchTo(oldcontext);
+	/*
+	 * While not pretty, it's ok to not shut down this context, but instead
+	 * rely on the containing memory context being reset, as
+	 * ExecBuildGroupingEqual() only builds a very simple expression calling
+	 * functions (i.e. nothing that'd employ RegisterExprContextCallback()).
+	 */
+	hashtable->exprcontext = CreateStandaloneExprContext();
 
-	hashtable->exprcontext = CreateExprContext(parent->state);
+	MemoryContextSwitchTo(oldcontext);
 
 	return hashtable;
 }


[parent: 0edef16d76be]