Fix small memory leak in partial-aggregate deserialization functions.

A deserialize function's result is short-lived data during partial
aggregation, since we're just going to pass it to the combine function
and then it's of no use anymore.  However, the built-in deserialize
functions allocated their results in the aggregate state context,
resulting in a query-lifespan memory leak.  It's probably not possible for
this to amount to anything much at present, since the number of leaked
results would only be the number of worker processes.  But it might become
a problem in future.  To fix, don't use the same convenience subroutine for
setting up results that the aggregate transition functions use.

David Rowley

Report: <10050.1466637736@sss.pgh.pa.us>

src/backend/utils/adt/numeric.c

@@ -3176,6 +3176,22 @@ makeNumericAggState(FunctionCallInfo fcinfo, bool calcSumX2)
 	return state;
 }
 
+/*
+ * Like makeNumericAggState(), but allocate the state in the current memory
+ * context.
+ */
+static NumericAggState *
+makeNumericAggStateCurrentContext(bool calcSumX2)
+{
+	NumericAggState *state;
+
+	state = (NumericAggState *) palloc0(sizeof(NumericAggState));
+	state->calcSumX2 = calcSumX2;
+	state->agg_context = CurrentMemoryContext;
+
+	return state;
+}
+
 /*
  * Accumulate a new input value for numeric aggregate functions.
  */
@@ -3374,7 +3390,7 @@ numeric_combine(PG_FUNCTION_ARGS)
 	{
 		old_context = MemoryContextSwitchTo(agg_context);
 
-		state1 = makeNumericAggState(fcinfo, true);
+		state1 = makeNumericAggStateCurrentContext(true);
 		state1->N = state2->N;
 		state1->NaNcount = state2->NaNcount;
 		state1->maxScale = state2->maxScale;
@@ -3465,7 +3481,7 @@ numeric_avg_combine(PG_FUNCTION_ARGS)
 	{
 		old_context = MemoryContextSwitchTo(agg_context);
 
-		state1 = makeNumericAggState(fcinfo, false);
+		state1 = makeNumericAggStateCurrentContext(false);
 		state1->N = state2->N;
 		state1->NaNcount = state2->NaNcount;
 		state1->maxScale = state2->maxScale;
@@ -3579,12 +3595,12 @@ numeric_avg_deserialize(PG_FUNCTION_ARGS)
 
 	/*
 	 * Copy the bytea into a StringInfo so that we can "receive" it using the
-	 * standard pq API.
+	 * standard recv-function infrastructure.
 	 */
 	initStringInfo(&buf);
 	appendBinaryStringInfo(&buf, VARDATA(sstate), VARSIZE(sstate) - VARHDRSZ);
 
-	result = makeNumericAggState(fcinfo, false);
+	result = makeNumericAggStateCurrentContext(false);
 
 	/* N */
 	result->N = pq_getmsgint64(&buf);
@@ -3691,12 +3707,12 @@ numeric_deserialize(PG_FUNCTION_ARGS)
 
 	/*
 	 * Copy the bytea into a StringInfo so that we can "receive" it using the
-	 * standard pq API.
+	 * standard recv-function infrastructure.
 	 */
 	initStringInfo(&buf);
 	appendBinaryStringInfo(&buf, VARDATA(sstate), VARSIZE(sstate) - VARHDRSZ);
 
-	result = makeNumericAggState(fcinfo, false);
+	result = makeNumericAggStateCurrentContext(false);
 
 	/* N */
 	result->N = pq_getmsgint64(&buf);
@@ -3803,6 +3819,21 @@ makeInt128AggState(FunctionCallInfo fcinfo, bool calcSumX2)
 	return state;
 }
 
+/*
+ * Like makeInt128AggState(), but allocate the state in the current memory
+ * context.
+ */
+static Int128AggState *
+makeInt128AggStateCurrentContext(bool calcSumX2)
+{
+	Int128AggState *state;
+
+	state = (Int128AggState *) palloc0(sizeof(Int128AggState));
+	state->calcSumX2 = calcSumX2;
+
+	return state;
+}
+
 /*
  * Accumulate a new input value for 128-bit aggregate functions.
  */
@@ -3831,9 +3862,11 @@ do_int128_discard(Int128AggState *state, int128 newval)
 
 typedef Int128AggState PolyNumAggState;
 #define makePolyNumAggState makeInt128AggState
+#define makePolyNumAggStateCurrentContext makeInt128AggStateCurrentContext
 #else
 typedef NumericAggState PolyNumAggState;
 #define makePolyNumAggState makeNumericAggState
+#define makePolyNumAggStateCurrentContext makeNumericAggStateCurrentContext
 #endif
 
 Datum
@@ -4072,12 +4105,12 @@ numeric_poly_deserialize(PG_FUNCTION_ARGS)
 
 	/*
 	 * Copy the bytea into a StringInfo so that we can "receive" it using the
-	 * standard pq API.
+	 * standard recv-function infrastructure.
 	 */
 	initStringInfo(&buf);
 	appendBinaryStringInfo(&buf, VARDATA(sstate), VARSIZE(sstate) - VARHDRSZ);
 
-	result = makePolyNumAggState(fcinfo, false);
+	result = makePolyNumAggStateCurrentContext(false);
 
 	/* N */
 	result->N = pq_getmsgint64(&buf);
@@ -4210,7 +4243,8 @@ int8_avg_combine(PG_FUNCTION_ARGS)
 
 /*
  * int8_avg_serialize
- *		Serialize PolyNumAggState into bytea using the standard pq API.
+ *		Serialize PolyNumAggState into bytea using the standard
+ *		recv-function infrastructure.
  */
 Datum
 int8_avg_serialize(PG_FUNCTION_ARGS)
@@ -4284,12 +4318,12 @@ int8_avg_deserialize(PG_FUNCTION_ARGS)
 
 	/*
 	 * Copy the bytea into a StringInfo so that we can "receive" it using the
-	 * standard pq API.
+	 * standard recv-function infrastructure.
 	 */
 	initStringInfo(&buf);
 	appendBinaryStringInfo(&buf, VARDATA(sstate), VARSIZE(sstate) - VARHDRSZ);
 
-	result = makePolyNumAggState(fcinfo, false);
+	result = makePolyNumAggStateCurrentContext(false);
 
 	/* N */
 	result->N = pq_getmsgint64(&buf);