Prevent memory leaks from accumulating across printtup() calls.

tglsfdc · tglsfdc · commit b006f4ddb988 · 2013-11-03T11:33:05.000-05:00
Historically, printtup() has assumed that it could prevent memory leakage
by pfree'ing the string result of each output function and manually
managing detoasting of toasted values.  This amounts to assuming that
datatype output functions never leak any memory internally; an assumption
we've already decided to be bogus elsewhere, for example in COPY OUT.
range_out in particular is known to leak multiple kilobytes per call, as
noted in bug #8573 from Godfried Vanluffelen.  While we could go in and fix
that leak, it wouldn't be very notationally convenient, and in any case
there have been and undoubtedly will again be other leaks in other output
functions.  So what seems like the best solution is to run the output
functions in a temporary memory context that can be reset after each row,
as we're doing in COPY OUT.  Some quick experimentation suggests this is
actually a tad faster than the retail pfree's anyway.

This patch fixes all the variants of printtup, except for debugtup()
which is used in standalone mode.  It doesn't seem worth worrying
about query-lifespan leaks in standalone mode, and fixing that case
would be a bit tedious since debugtup() doesn't currently have any
startup or shutdown functions.

While at it, remove manual detoast management from several other
output-function call sites that had copied it from printtup().  This
doesn't make a lot of difference right now, but in view of recent
discussions about supporting "non-flattened" Datums, we're going to
want that code gone eventually anyway.

Back-patch to 9.2 where range_out was introduced.  We might eventually
decide to back-patch this further, but in the absence of known major
leaks in older output functions, I'll refrain for now.
diff --git a/src/backend/access/common/printtup.c b/src/backend/access/common/printtup.c
@@ -21,6 +21,7 @@
 #include "tcop/pquery.h"
 #include "utils/lsyscache.h"
 #include "utils/memdebug.h"
+#include "utils/memutils.h"
 
 
 static void printtup_startup(DestReceiver *self, int operation,
@@ -61,6 +62,7 @@ typedef struct
 	TupleDesc	attrinfo;		/* The attr info we are set up for */
 	int			nattrs;
 	PrinttupAttrInfo *myinfo;	/* Cached info about each attr */
+	MemoryContext tmpcontext;	/* Memory context for per-row workspace */
 } DR_printtup;
 
 /* ----------------
@@ -87,6 +89,7 @@ printtup_create_DR(CommandDest dest)
 	self->attrinfo = NULL;
 	self->nattrs = 0;
 	self->myinfo = NULL;
+	self->tmpcontext = NULL;
 
 	return (DestReceiver *) self;
 }
@@ -124,6 +127,18 @@ printtup_startup(DestReceiver *self, int operation, TupleDesc typeinfo)
 	DR_printtup *myState = (DR_printtup *) self;
 	Portal		portal = myState->portal;
 
+	/*
+	 * Create a temporary memory context that we can reset once per row to
+	 * recover palloc'd memory.  This avoids any problems with leaks inside
+	 * datatype output routines, and should be faster than retail pfree's
+	 * anyway.
+	 */
+	myState->tmpcontext = AllocSetContextCreate(CurrentMemoryContext,
+												"printtup",
+												ALLOCSET_DEFAULT_MINSIZE,
+												ALLOCSET_DEFAULT_INITSIZE,
+												ALLOCSET_DEFAULT_MAXSIZE);
+
 	if (PG_PROTOCOL_MAJOR(FrontendProtocol) < 3)
 	{
 		/*
@@ -289,6 +304,7 @@ printtup(TupleTableSlot *slot, DestReceiver *self)
 {
 	TupleDesc	typeinfo = slot->tts_tupleDescriptor;
 	DR_printtup *myState = (DR_printtup *) self;
+	MemoryContext oldcontext;
 	StringInfoData buf;
 	int			natts = typeinfo->natts;
 	int			i;
@@ -300,8 +316,11 @@ printtup(TupleTableSlot *slot, DestReceiver *self)
 	/* Make sure the tuple is fully deconstructed */
 	slot_getallattrs(slot);
 
+	/* Switch into per-row context so we can recover memory below */
+	oldcontext = MemoryContextSwitchTo(myState->tmpcontext);
+
 	/*
-	 * Prepare a DataRow message
+	 * Prepare a DataRow message (note buffer is in per-row context)
 	 */
 	pq_beginmessage(&buf, 'D');
 
@@ -313,8 +332,7 @@ printtup(TupleTableSlot *slot, DestReceiver *self)
 	for (i = 0; i < natts; ++i)
 	{
 		PrinttupAttrInfo *thisState = myState->myinfo + i;
-		Datum		origattr = slot->tts_values[i],
-					attr;
+		Datum		attr = slot->tts_values[i];
 
 		if (slot->tts_isnull[i])
 		{
@@ -323,30 +341,15 @@ printtup(TupleTableSlot *slot, DestReceiver *self)
 		}
 
 		/*
-		 * If we have a toasted datum, forcibly detoast it here to avoid
-		 * memory leakage inside the type's output routine.
-		 *
-		 * Here we catch undefined bytes in tuples that are returned to the
+		 * Here we catch undefined bytes in datums that are returned to the
 		 * client without hitting disk; see comments at the related check in
-		 * PageAddItem().  Whether to test before or after detoast is somewhat
-		 * arbitrary, as is whether to test external/compressed data at all.
-		 * Undefined bytes in the pre-toast datum will have triggered Valgrind
-		 * errors in the compressor or toaster; any error detected here for
-		 * such datums would indicate an (unlikely) bug in a type-independent
-		 * facility.  Therefore, this test is most useful for uncompressed,
-		 * non-external datums.
-		 *
-		 * We don't presently bother checking non-varlena datums for undefined
-		 * data.  PageAddItem() does check them.
+		 * PageAddItem().  This test is most useful for uncompressed,
+		 * non-external datums, but we're quite likely to see such here when
+		 * testing new C functions.
 		 */
 		if (thisState->typisvarlena)
-		{
-			VALGRIND_CHECK_MEM_IS_DEFINED(origattr, VARSIZE_ANY(origattr));
-
-			attr = PointerGetDatum(PG_DETOAST_DATUM(origattr));
-		}
-		else
-			attr = origattr;
+			VALGRIND_CHECK_MEM_IS_DEFINED(DatumGetPointer(attr),
+										  VARSIZE_ANY(attr));
 
 		if (thisState->format == 0)
 		{
@@ -355,7 +358,6 @@ printtup(TupleTableSlot *slot, DestReceiver *self)
 
 			outputstr = OutputFunctionCall(&thisState->finfo, attr);
 			pq_sendcountedtext(&buf, outputstr, strlen(outputstr), false);
-			pfree(outputstr);
 		}
 		else
 		{
@@ -366,15 +368,14 @@ printtup(TupleTableSlot *slot, DestReceiver *self)
 			pq_sendint(&buf, VARSIZE(outputbytes) - VARHDRSZ, 4);
 			pq_sendbytes(&buf, VARDATA(outputbytes),
 						 VARSIZE(outputbytes) - VARHDRSZ);
-			pfree(outputbytes);
 		}
-
-		/* Clean up detoasted copy, if any */
-		if (DatumGetPointer(attr) != DatumGetPointer(origattr))
-			pfree(DatumGetPointer(attr));
 	}
 
 	pq_endmessage(&buf);
+
+	/* Return to caller's context, and flush row's temporary memory */
+	MemoryContextSwitchTo(oldcontext);
+	MemoryContextReset(myState->tmpcontext);
 }
 
 /* ----------------
@@ -386,6 +387,7 @@ printtup_20(TupleTableSlot *slot, DestReceiver *self)
 {
 	TupleDesc	typeinfo = slot->tts_tupleDescriptor;
 	DR_printtup *myState = (DR_printtup *) self;
+	MemoryContext oldcontext;
 	StringInfoData buf;
 	int			natts = typeinfo->natts;
 	int			i,
@@ -399,6 +401,9 @@ printtup_20(TupleTableSlot *slot, DestReceiver *self)
 	/* Make sure the tuple is fully deconstructed */
 	slot_getallattrs(slot);
 
+	/* Switch into per-row context so we can recover memory below */
+	oldcontext = MemoryContextSwitchTo(myState->tmpcontext);
+
 	/*
 	 * tell the frontend to expect new tuple data (in ASCII style)
 	 */
@@ -430,34 +435,23 @@ printtup_20(TupleTableSlot *slot, DestReceiver *self)
 	for (i = 0; i < natts; ++i)
 	{
 		PrinttupAttrInfo *thisState = myState->myinfo + i;
-		Datum		origattr = slot->tts_values[i],
-					attr;
+		Datum		attr = slot->tts_values[i];
 		char	   *outputstr;
 
 		if (slot->tts_isnull[i])
 			continue;
 
 		Assert(thisState->format == 0);
 
-		/*
-		 * If we have a toasted datum, forcibly detoast it here to avoid
-		 * memory leakage inside the type's output routine.
-		 */
-		if (thisState->typisvarlena)
-			attr = PointerGetDatum(PG_DETOAST_DATUM(origattr));
-		else
-			attr = origattr;
-
 		outputstr = OutputFunctionCall(&thisState->finfo, attr);
 		pq_sendcountedtext(&buf, outputstr, strlen(outputstr), true);
-		pfree(outputstr);
-
-		/* Clean up detoasted copy, if any */
-		if (DatumGetPointer(attr) != DatumGetPointer(origattr))
-			pfree(DatumGetPointer(attr));
 	}
 
 	pq_endmessage(&buf);
+
+	/* Return to caller's context, and flush row's temporary memory */
+	MemoryContextSwitchTo(oldcontext);
+	MemoryContextReset(myState->tmpcontext);
 }
 
 /* ----------------
@@ -474,6 +468,10 @@ printtup_shutdown(DestReceiver *self)
 	myState->myinfo = NULL;
 
 	myState->attrinfo = NULL;
+
+	if (myState->tmpcontext)
+		MemoryContextDelete(myState->tmpcontext);
+	myState->tmpcontext = NULL;
 }
 
 /* ----------------
@@ -536,39 +534,23 @@ debugtup(TupleTableSlot *slot, DestReceiver *self)
 	TupleDesc	typeinfo = slot->tts_tupleDescriptor;
 	int			natts = typeinfo->natts;
 	int			i;
-	Datum		origattr,
-				attr;
+	Datum		attr;
 	char	   *value;
 	bool		isnull;
 	Oid			typoutput;
 	bool		typisvarlena;
 
 	for (i = 0; i < natts; ++i)
 	{
-		origattr = slot_getattr(slot, i + 1, &isnull);
+		attr = slot_getattr(slot, i + 1, &isnull);
 		if (isnull)
 			continue;
 		getTypeOutputInfo(typeinfo->attrs[i]->atttypid,
 						  &typoutput, &typisvarlena);
 
-		/*
-		 * If we have a toasted datum, forcibly detoast it here to avoid
-		 * memory leakage inside the type's output routine.
-		 */
-		if (typisvarlena)
-			attr = PointerGetDatum(PG_DETOAST_DATUM(origattr));
-		else
-			attr = origattr;
-
 		value = OidOutputFunctionCall(typoutput, attr);
 
 		printatt((unsigned) i + 1, typeinfo->attrs[i], value);
-
-		pfree(value);
-
-		/* Clean up detoasted copy, if any */
-		if (DatumGetPointer(attr) != DatumGetPointer(origattr))
-			pfree(DatumGetPointer(attr));
 	}
 	printf("\t----\n");
 }
@@ -587,6 +569,7 @@ printtup_internal_20(TupleTableSlot *slot, DestReceiver *self)
 {
 	TupleDesc	typeinfo = slot->tts_tupleDescriptor;
 	DR_printtup *myState = (DR_printtup *) self;
+	MemoryContext oldcontext;
 	StringInfoData buf;
 	int			natts = typeinfo->natts;
 	int			i,
@@ -600,6 +583,9 @@ printtup_internal_20(TupleTableSlot *slot, DestReceiver *self)
 	/* Make sure the tuple is fully deconstructed */
 	slot_getallattrs(slot);
 
+	/* Switch into per-row context so we can recover memory below */
+	oldcontext = MemoryContextSwitchTo(myState->tmpcontext);
+
 	/*
 	 * tell the frontend to expect new tuple data (in binary style)
 	 */
@@ -631,35 +617,23 @@ printtup_internal_20(TupleTableSlot *slot, DestReceiver *self)
 	for (i = 0; i < natts; ++i)
 	{
 		PrinttupAttrInfo *thisState = myState->myinfo + i;
-		Datum		origattr = slot->tts_values[i],
-					attr;
+		Datum		attr = slot->tts_values[i];
 		bytea	   *outputbytes;
 
 		if (slot->tts_isnull[i])
 			continue;
 
 		Assert(thisState->format == 1);
 
-		/*
-		 * If we have a toasted datum, forcibly detoast it here to avoid
-		 * memory leakage inside the type's output routine.
-		 */
-		if (thisState->typisvarlena)
-			attr = PointerGetDatum(PG_DETOAST_DATUM(origattr));
-		else
-			attr = origattr;
-
 		outputbytes = SendFunctionCall(&thisState->finfo, attr);
-		/* We assume the result will not have been toasted */
 		pq_sendint(&buf, VARSIZE(outputbytes) - VARHDRSZ, 4);
 		pq_sendbytes(&buf, VARDATA(outputbytes),
 					 VARSIZE(outputbytes) - VARHDRSZ);
-		pfree(outputbytes);
-
-		/* Clean up detoasted copy, if any */
-		if (DatumGetPointer(attr) != DatumGetPointer(origattr))
-			pfree(DatumGetPointer(attr));
 	}
 
 	pq_endmessage(&buf);
+
+	/* Return to caller's context, and flush row's temporary memory */
+	MemoryContextSwitchTo(oldcontext);
+	MemoryContextReset(myState->tmpcontext);
 }
diff --git a/src/backend/bootstrap/bootstrap.c b/src/backend/bootstrap/bootstrap.c
@@ -835,7 +835,6 @@ InsertOneValue(char *value, int i)
 	Oid			typioparam;
 	Oid			typinput;
 	Oid			typoutput;
-	char	   *prt;
 
 	AssertArg(i >= 0 && i < MAXATTR);
 
@@ -849,9 +848,14 @@ InsertOneValue(char *value, int i)
 						  &typinput, &typoutput);
 
 	values[i] = OidInputFunctionCall(typinput, value, typioparam, -1);
-	prt = OidOutputFunctionCall(typoutput, values[i]);
-	elog(DEBUG4, "inserted -> %s", prt);
-	pfree(prt);
+
+	/*
+	 * We use ereport not elog here so that parameters aren't evaluated unless
+	 * the message is going to be printed, which generally it isn't
+	 */
+	ereport(DEBUG4,
+			(errmsg_internal("inserted -> %s",
+							 OidOutputFunctionCall(typoutput, values[i]))));
 }
 
 /* ----------------
diff --git a/src/backend/executor/spi.c b/src/backend/executor/spi.c
@@ -869,9 +869,7 @@ SPI_fname(TupleDesc tupdesc, int fnumber)
 char *
 SPI_getvalue(HeapTuple tuple, TupleDesc tupdesc, int fnumber)
 {
-	char	   *result;
-	Datum		origval,
-				val;
+	Datum		val;
 	bool		isnull;
 	Oid			typoid,
 				foutoid;
@@ -886,7 +884,7 @@ SPI_getvalue(HeapTuple tuple, TupleDesc tupdesc, int fnumber)
 		return NULL;
 	}
 
-	origval = heap_getattr(tuple, fnumber, tupdesc, &isnull);
+	val = heap_getattr(tuple, fnumber, tupdesc, &isnull);
 	if (isnull)
 		return NULL;
 
@@ -897,22 +895,7 @@ SPI_getvalue(HeapTuple tuple, TupleDesc tupdesc, int fnumber)
 
 	getTypeOutputInfo(typoid, &foutoid, &typisvarlena);
 
-	/*
-	 * If we have a toasted datum, forcibly detoast it here to avoid memory
-	 * leakage inside the type's output routine.
-	 */
-	if (typisvarlena)
-		val = PointerGetDatum(PG_DETOAST_DATUM(origval));
-	else
-		val = origval;
-
-	result = OidOutputFunctionCall(foutoid, val);
-
-	/* Clean up detoasted copy, if any */
-	if (val != origval)
-		pfree(DatumGetPointer(val));
-
-	return result;
+	return OidOutputFunctionCall(foutoid, val);
 }
 
 Datum
diff --git a/src/backend/utils/adt/rowtypes.c b/src/backend/utils/adt/rowtypes.c
