Rename another "hash_mem" local variable.

Missed by my commit 564ce621.

Backpatch: 13-, where disk-based hash aggregation was introduced.

Author: petergeoghegan

src/backend/executor/nodeAgg.c

@@ -1839,15 +1839,15 @@ hash_agg_check_limits(AggState *aggstate)
 	uint64		ngroups = aggstate->hash_ngroups_current;
 	Size		meta_mem = MemoryContextMemAllocated(aggstate->hash_metacxt,
 													 true);
-	Size		hash_mem = MemoryContextMemAllocated(aggstate->hashcontext->ecxt_per_tuple_memory,
-													 true);
+	Size		hashkey_mem = MemoryContextMemAllocated(aggstate->hashcontext->ecxt_per_tuple_memory,
+														true);
 
 	/*
 	 * Don't spill unless there's at least one group in the hash table so we
 	 * can be sure to make progress even in edge cases.
 	 */
 	if (aggstate->hash_ngroups_current > 0 &&
-		(meta_mem + hash_mem > aggstate->hash_mem_limit ||
+		(meta_mem + hashkey_mem > aggstate->hash_mem_limit ||
 		 ngroups > aggstate->hash_ngroups_limit))
 	{
 		hash_agg_enter_spill_mode(aggstate);
@@ -1898,7 +1898,7 @@ static void
 hash_agg_update_metrics(AggState *aggstate, bool from_tape, int npartitions)
 {
 	Size		meta_mem;
-	Size		hash_mem;
+	Size		hashkey_mem;
 	Size		buffer_mem;
 	Size		total_mem;
 
@@ -1910,15 +1910,15 @@ hash_agg_update_metrics(AggState *aggstate, bool from_tape, int npartitions)
 	meta_mem = MemoryContextMemAllocated(aggstate->hash_metacxt, true);
 
 	/* memory for the group keys and transition states */
-	hash_mem = MemoryContextMemAllocated(aggstate->hashcontext->ecxt_per_tuple_memory, true);
+	hashkey_mem = MemoryContextMemAllocated(aggstate->hashcontext->ecxt_per_tuple_memory, true);
 
 	/* memory for read/write tape buffers, if spilled */
 	buffer_mem = npartitions * HASHAGG_WRITE_BUFFER_SIZE;
 	if (from_tape)
 		buffer_mem += HASHAGG_READ_BUFFER_SIZE;
 
 	/* update peak mem */
-	total_mem = meta_mem + hash_mem + buffer_mem;
+	total_mem = meta_mem + hashkey_mem + buffer_mem;
 	if (total_mem > aggstate->hash_mem_peak)
 		aggstate->hash_mem_peak = total_mem;
 
@@ -1936,7 +1936,7 @@ hash_agg_update_metrics(AggState *aggstate, bool from_tape, int npartitions)
 	{
 		aggstate->hashentrysize =
 			sizeof(TupleHashEntryData) +
-			(hash_mem / (double) aggstate->hash_ngroups_current);
+			(hashkey_mem / (double) aggstate->hash_ngroups_current);
 	}
 }