From c1f8fb9bfb0d2a89f646b3186a004d6e4ebdecb4 Mon Sep 17 00:00:00 2001 From: Tom Lane Date: Thu, 19 Jun 2014 22:13:47 -0400 Subject: Avoid leaking memory while evaluating arguments for a table function. ExecMakeTableFunctionResult evaluated the arguments for a function-in-FROM in the query-lifespan memory context. This is insignificant in simple cases where the function relation is scanned only once; but if the function is in a sub-SELECT or is on the inside of a nested loop, any memory consumed during argument evaluation can add up quickly. (The potential for trouble here had been foreseen long ago, per existing comments; but we'd not previously seen a complaint from the field about it.) To fix, create an additional temporary context just for this purpose. Per an example from MauMau. Back-patch to all active branches. --- src/backend/executor/execQual.c | 15 +++++++++++---- 1 file changed, 11 insertions(+), 4 deletions(-) (limited to 'src/backend/executor/execQual.c') diff --git a/src/backend/executor/execQual.c b/src/backend/executor/execQual.c index ab05ec226ea..c6f31a0ad0b 100644 --- a/src/backend/executor/execQual.c +++ b/src/backend/executor/execQual.c @@ -2002,6 +2002,7 @@ ExecMakeFunctionResultNoSets(FuncExprState *fcache, Tuplestorestate * ExecMakeTableFunctionResult(ExprState *funcexpr, ExprContext *econtext, + MemoryContext argContext, TupleDesc expectedDesc, bool randomAccess) { @@ -2083,12 +2084,18 @@ ExecMakeTableFunctionResult(ExprState *funcexpr, /* * Evaluate the function's argument list. * - * Note: ideally, we'd do this in the per-tuple context, but then the - * argument values would disappear when we reset the context in the - * inner loop. So do it in caller context. Perhaps we should make a - * separate context just to hold the evaluated arguments? + * We can't do this in the per-tuple context: the argument values + * would disappear when we reset that context in the inner loop. And + * the caller's CurrentMemoryContext is typically a query-lifespan + * context, so we don't want to leak memory there. We require the + * caller to pass a separate memory context that can be used for this, + * and can be reset each time through to avoid bloat. */ + MemoryContextReset(argContext); + oldcontext = MemoryContextSwitchTo(argContext); argDone = ExecEvalFuncArgs(&fcinfo, fcache->args, econtext); + MemoryContextSwitchTo(oldcontext); + /* We don't allow sets in the arguments of the table function */ if (argDone != ExprSingleResult) ereport(ERROR, -- cgit v1.2.3