QQL: reduce memory consumption of group by

java/timebase/qql/src/main/java/com/epam/deltix/qsrv/hf/tickdb/lang/runtime/FilterIMSImpl.java

@@ -32,6 +32,7 @@
 import com.epam.deltix.qsrv.hf.tickdb.pub.DXTickDB;
 import com.epam.deltix.qsrv.hf.tickdb.pub.query.FixedMessageSource;
 import com.epam.deltix.qsrv.hf.tickdb.pub.query.InstrumentMessageSource;
+import com.epam.deltix.qsrv.util.json.DateFormatter;
 import com.epam.deltix.util.collections.IndexedArrayList;
 
 import java.util.Arrays;
@@ -86,6 +87,8 @@ public abstract class FilterIMSImpl
     private long firstMessageTimestamp = Long.MIN_VALUE;
 
     protected long aggregatedMessages;
+
+    private final DateFormatter datetimeFormatter = new DateFormatter();
 
     protected FilterIMSImpl (
         InstrumentMessageSource             source,
@@ -553,4 +556,8 @@ private int getParamIndex(int n) {
         return n & ~(TimestampLimits.EXCLUSIVE_BIT | TimestampLimits.NANOS_BIT);
     }
 
+    public DateFormatter datetimeFormatter() {
+        return datetimeFormatter;
+    }
+
 }

java/timebase/qql/src/main/java/com/epam/deltix/qsrv/hf/tickdb/lang/runtime/FilterState.java

@@ -48,8 +48,6 @@ public abstract class FilterState {
 
     private final FilterIMSImpl filter;
 
-    private final DateFormatter datetimeFormatter = new DateFormatter();
-
     private final Introspector introspector = Introspector.createEmptyMessageIntrospector();
 
     public FilterState(FilterIMSImpl filter) {
@@ -126,7 +124,7 @@ public EnumClassDescriptor getEnumDescriptor(String name) {
     }
 
     public DateFormatter datetimeFormatter() {
-        return datetimeFormatter;
+        return filter.datetimeFormatter();
     }
 
     public void setHavingAccepted(boolean havingAccepted) {

java/timebase/qql/src/main/java/com/epam/deltix/qsrv/hf/tickdb/lang/runtime/GroupByFilterState.java

@@ -28,7 +28,7 @@
  */
 public abstract class GroupByFilterState extends FilterState implements Serializer<GroupByFilterState> {
 
-    protected final MemoryDataOutput mdo = new MemoryDataOutput();
+    protected final MemoryDataOutput mdo = new MemoryDataOutput(16);
     protected final MemoryDataInput mdi = new MemoryDataInput();
 
     public GroupByFilterState(FilterIMSImpl filter) {