Fix memory leaks in record_out() and record_send().

tglsfdc · tglsfdc · commit c027d84c81d5 · 2012-11-13T14:44:56.000-05:00
record_out() leaks memory: it fails to free the strings returned by the
per-column output functions, and also is careless about detoasted values.
This results in a query-lifespan memory leakage when returning composite
values to the client, because printtup() runs the output functions in the
query-lifespan memory context.  Fix it to handle these issues the same way
printtup() does.  Also fix a similar leakage in record_send().

(At some point we might want to try to run output functions in
shorter-lived memory contexts, so that we don't need a zero-leakage policy
for them.  But that would be a significantly more invasive patch, which
doesn't seem like material for back-patching.)

In passing, use appendStringInfoCharMacro instead of appendStringInfoChar
in the innermost data-copying loop of record_out, to try to shave a few
cycles from this function's runtime.

Per trouble report from Carlos Henrique Reimer.  Back-patch to all
supported versions.
diff --git a/src/backend/utils/adt/rowtypes.c b/src/backend/utils/adt/rowtypes.c
@@ -32,6 +32,7 @@ typedef struct ColumnIOData
 	Oid			column_type;
 	Oid			typiofunc;
 	Oid			typioparam;
+	bool		typisvarlena;
 	FmgrInfo	proc;
 } ColumnIOData;
 
@@ -340,6 +341,7 @@ record_out(PG_FUNCTION_ARGS)
 	{
 		ColumnIOData *column_info = &my_extra->columns[i];
 		Oid			column_type = tupdesc->attrs[i]->atttypid;
+		Datum		attr;
 		char	   *value;
 		char	   *tmp;
 		bool		nq;
@@ -363,17 +365,24 @@ record_out(PG_FUNCTION_ARGS)
 		 */
 		if (column_info->column_type != column_type)
 		{
-			bool		typIsVarlena;
-
 			getTypeOutputInfo(column_type,
 							  &column_info->typiofunc,
-							  &typIsVarlena);
+							  &column_info->typisvarlena);
 			fmgr_info_cxt(column_info->typiofunc, &column_info->proc,
 						  fcinfo->flinfo->fn_mcxt);
 			column_info->column_type = column_type;
 		}
 
-		value = OutputFunctionCall(&column_info->proc, values[i]);
+		/*
+		 * If we have a toasted datum, forcibly detoast it here to avoid
+		 * memory leakage inside the type's output routine.
+		 */
+		if (column_info->typisvarlena)
+			attr = PointerGetDatum(PG_DETOAST_DATUM(values[i]));
+		else
+			attr = values[i];
+
+		value = OutputFunctionCall(&column_info->proc, attr);
 
 		/* Detect whether we need double quotes for this value */
 		nq = (value[0] == '\0');	/* force quotes for empty string */
@@ -392,17 +401,23 @@ record_out(PG_FUNCTION_ARGS)
 
 		/* And emit the string */
 		if (nq)
-			appendStringInfoChar(&buf, '"');
+			appendStringInfoCharMacro(&buf, '"');
 		for (tmp = value; *tmp; tmp++)
 		{
 			char		ch = *tmp;
 
 			if (ch == '"' || ch == '\\')
-				appendStringInfoChar(&buf, ch);
-			appendStringInfoChar(&buf, ch);
+				appendStringInfoCharMacro(&buf, ch);
+			appendStringInfoCharMacro(&buf, ch);
 		}
 		if (nq)
-			appendStringInfoChar(&buf, '"');
+			appendStringInfoCharMacro(&buf, '"');
+
+		pfree(value);
+
+		/* Clean up detoasted copy, if any */
+		if (DatumGetPointer(attr) != DatumGetPointer(values[i]))
+			pfree(DatumGetPointer(attr));
 	}
 
 	appendStringInfoChar(&buf, ')');
@@ -690,6 +705,7 @@ record_send(PG_FUNCTION_ARGS)
 	{
 		ColumnIOData *column_info = &my_extra->columns[i];
 		Oid			column_type = tupdesc->attrs[i]->atttypid;
+		Datum		attr;
 		bytea	   *outputbytes;
 
 		/* Ignore dropped columns in datatype */
@@ -710,23 +726,35 @@ record_send(PG_FUNCTION_ARGS)
 		 */
 		if (column_info->column_type != column_type)
 		{
-			bool		typIsVarlena;
-
 			getTypeBinaryOutputInfo(column_type,
 									&column_info->typiofunc,
-									&typIsVarlena);
+									&column_info->typisvarlena);
 			fmgr_info_cxt(column_info->typiofunc, &column_info->proc,
 						  fcinfo->flinfo->fn_mcxt);
 			column_info->column_type = column_type;
 		}
 
-		outputbytes = SendFunctionCall(&column_info->proc, values[i]);
+		/*
+		 * If we have a toasted datum, forcibly detoast it here to avoid
+		 * memory leakage inside the type's output routine.
+		 */
+		if (column_info->typisvarlena)
+			attr = PointerGetDatum(PG_DETOAST_DATUM(values[i]));
+		else
+			attr = values[i];
+
+		outputbytes = SendFunctionCall(&column_info->proc, 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(values[i]))
+			pfree(DatumGetPointer(attr));
 	}
 
 	pfree(values);
