Ensure fixed iteration order of GroupId assignments

Author: kasiafi

core/trino-main/src/main/java/io/trino/sql/planner/optimizations/SymbolMapper.java

@@ -58,8 +58,8 @@
 import io.trino.sql.planner.rowpattern.ValuePointer;
 import io.trino.sql.planner.rowpattern.ir.IrLabel;
 
-import java.util.HashMap;
 import java.util.HashSet;
+import java.util.LinkedHashMap;
 import java.util.LinkedHashSet;
 import java.util.List;
 import java.util.Map;
@@ -216,7 +216,7 @@ public Aggregation map(Aggregation aggregation)
 
     public GroupIdNode map(GroupIdNode node, PlanNode source)
     {
-        Map<Symbol, Symbol> newGroupingMappings = new HashMap<>();
+        Map<Symbol, Symbol> newGroupingMappings = new LinkedHashMap<>();
         ImmutableList.Builder<List<Symbol>> newGroupingSets = ImmutableList.builder();
 
         for (List<Symbol> groupingSet : node.getGroupingSets()) {