diff --git a/src/backend/executor/execGrouping.c b/src/backend/executor/execGrouping.c
index 271bba17e4..c651084b57 100644
--- a/src/backend/executor/execGrouping.c
+++ b/src/backend/executor/execGrouping.c
@@ -138,7 +138,8 @@ execTuplesHashPrepare(int numCols,
  *	hashfunctions: datatype-specific hashing functions to use
  *	nbuckets: initial estimate of hashtable size
  *	additionalsize: size of data stored in ->additional
- *	tablecxt: memory context in which to store table and table entries
+ *	metacxt: memory context for long-lived allocation, but not per-entry data
+ *	tablecxt: memory context in which to store table entries
  *	tempcxt: short-lived context for evaluation hash and comparison functions
  *
  * The function arrays may be made with execTuplesHashPrepare().  Note they
@@ -149,14 +150,16 @@ execTuplesHashPrepare(int numCols,
  * storage that will live as long as the hashtable does.
  */
 TupleHashTable
-BuildTupleHashTable(PlanState *parent,
-					TupleDesc inputDesc,
-					int numCols, AttrNumber *keyColIdx,
-					Oid *eqfuncoids,
-					FmgrInfo *hashfunctions,
-					long nbuckets, Size additionalsize,
-					MemoryContext tablecxt, MemoryContext tempcxt,
-					bool use_variable_hash_iv)
+BuildTupleHashTableExt(PlanState *parent,
+					   TupleDesc inputDesc,
+					   int numCols, AttrNumber *keyColIdx,
+					   Oid *eqfuncoids,
+					   FmgrInfo *hashfunctions,
+					   long nbuckets, Size additionalsize,
+					   MemoryContext metacxt,
+					   MemoryContext tablecxt,
+					   MemoryContext tempcxt,
+					   bool use_variable_hash_iv)
 {
 	TupleHashTable hashtable;
 	Size		entrysize = sizeof(TupleHashEntryData) + additionalsize;
@@ -167,8 +170,9 @@ BuildTupleHashTable(PlanState *parent,
 	/* Limit initial table size request to not more than work_mem */
 	nbuckets = Min(nbuckets, (long) ((work_mem * 1024L) / entrysize));
 
-	hashtable = (TupleHashTable)
-		MemoryContextAlloc(tablecxt, sizeof(TupleHashTableData));
+	oldcontext = MemoryContextSwitchTo(metacxt);
+
+	hashtable = (TupleHashTable) palloc(sizeof(TupleHashTableData));
 
 	hashtable->numCols = numCols;
 	hashtable->keyColIdx = keyColIdx;
@@ -194,9 +198,7 @@ BuildTupleHashTable(PlanState *parent,
 	else
 		hashtable->hash_iv = 0;
 
-	hashtable->hashtab = tuplehash_create(tablecxt, nbuckets, hashtable);
-
-	oldcontext = MemoryContextSwitchTo(hashtable->tablecxt);
+	hashtable->hashtab = tuplehash_create(metacxt, nbuckets, hashtable);
 
 	/*
 	 * We copy the input tuple descriptor just for safety --- we assume all
@@ -223,6 +225,46 @@ BuildTupleHashTable(PlanState *parent,
 	return hashtable;
 }
 
+/*
+ * BuildTupleHashTable is a backwards-compatibilty wrapper for
+ * BuildTupleHashTableExt(), that allocates the hashtable's metadata in
+ * tablecxt. Note that hashtables created this way cannot be reset leak-free
+ * with ResetTupleHashTable().
+ */
+TupleHashTable
+BuildTupleHashTable(PlanState *parent,
+					TupleDesc inputDesc,
+					int numCols, AttrNumber *keyColIdx,
+					Oid *eqfuncoids,
+					FmgrInfo *hashfunctions,
+					long nbuckets, Size additionalsize,
+					MemoryContext tablecxt,
+					MemoryContext tempcxt,
+					bool use_variable_hash_iv)
+{
+	return BuildTupleHashTableExt(parent,
+								  inputDesc,
+								  numCols, keyColIdx,
+								  eqfuncoids,
+								  hashfunctions,
+								  nbuckets, additionalsize,
+								  tablecxt,
+								  tablecxt,
+								  tempcxt,
+								  use_variable_hash_iv);
+}
+
+/*
+ * Reset contents of the hashtable to be empty, preserving all the non-content
+ * state. Note that the tablecxt passed to BuildTupleHashTableExt() should
+ * also be reset, otherwise there will be leaks.
+ */
+void
+ResetTupleHashTable(TupleHashTable hashtable)
+{
+	tuplehash_reset(hashtable->hashtab);
+}
+
 /*
  * Find or create a hashtable entry for the tuple group containing the
  * given tuple.  The tuple must be the same type as the hashtable entries.
diff --git a/src/include/executor/executor.h b/src/include/executor/executor.h
index f82b51667f..97b1c0f67d 100644
--- a/src/include/executor/executor.h
+++ b/src/include/executor/executor.h
@@ -129,6 +129,15 @@ extern TupleHashTable BuildTupleHashTable(PlanState *parent,
 					long nbuckets, Size additionalsize,
 					MemoryContext tablecxt,
 					MemoryContext tempcxt, bool use_variable_hash_iv);
+extern TupleHashTable BuildTupleHashTableExt(PlanState *parent,
+					TupleDesc inputDesc,
+					int numCols, AttrNumber *keyColIdx,
+					Oid *eqfuncoids,
+					FmgrInfo *hashfunctions,
+					long nbuckets, Size additionalsize,
+					MemoryContext metacxt,
+					MemoryContext tablecxt,
+					MemoryContext tempcxt, bool use_variable_hash_iv);
 extern TupleHashEntry LookupTupleHashEntry(TupleHashTable hashtable,
 					 TupleTableSlot *slot,
 					 bool *isnew);
@@ -136,6 +145,7 @@ extern TupleHashEntry FindTupleHashEntry(TupleHashTable hashtable,
 				   TupleTableSlot *slot,
 				   ExprState *eqcomp,
 				   FmgrInfo *hashfunctions);
+extern void ResetTupleHashTable(TupleHashTable hashtable);
 
 /*
  * prototypes from functions in execJunk.c