Fixes memory leak in BytesRefLongBlockHash (elastic#137050)

Author: ncordon

docs/changelog/137050.yaml

@@ -0,0 +1,6 @@
+pr: 137050
+summary: Fixes memory leak in `BytesRefLongBlockHash`
+area: ES|QL
+type: bug
+issues:
+ - 137021

x-pack/plugin/esql/compute/src/main/java/org/elasticsearch/compute/aggregation/blockhash/BytesRefLongBlockHash.java

@@ -161,12 +161,15 @@ public Block[] getKeys() {
                 }
                 // TODO: make takeOwnershipOf work?
                 BytesRefArray bytes = BytesRefArray.deepCopy(bytesHash.hash.getBytesRefs());
+                BytesRefVector dict = null;
+
                 try {
-                    var dict = blockFactory.newBytesRefArrayVector(bytes, Math.toIntExact(bytes.size()));
+                    dict = blockFactory.newBytesRefArrayVector(bytes, Math.toIntExact(bytes.size()));
                     bytes = null; // transfer ownership to dict
                     k1 = new OrdinalBytesRefBlock(ordinals.build(), dict);
+                    dict = null;  // transfer ownership to k1
                 } finally {
-                    Releasables.closeExpectNoException(bytes);
+                    Releasables.closeExpectNoException(bytes, dict);
                 }
                 k2 = longs.build();
             } finally {