Use unsorted source for time_series aggs without rates

Author: dnhatn

server/src/main/java/org/elasticsearch/index/mapper/TimeSeriesIdFieldMapper.java

@@ -132,6 +132,11 @@ public IndexFieldData.Builder fielddataBuilder(FieldDataContext fieldDataContext
         public Query termQuery(Object value, SearchExecutionContext context) {
             throw new IllegalArgumentException("[" + NAME + "] is not searchable");
         }
+
+        @Override
+        public BlockLoader blockLoader(BlockLoaderContext blContext) {
+            return new BlockDocValuesReader.BytesRefsFromOrdsBlockLoader(name());
+        }
     }
 
     private final boolean useDocValuesSkipper;

x-pack/plugin/esql/src/main/java/org/elasticsearch/xpack/esql/optimizer/rules/logical/TranslateTimeSeriesAggregate.java

@@ -7,6 +7,7 @@
 
 package org.elasticsearch.xpack.esql.optimizer.rules.logical;
 
+import org.elasticsearch.index.IndexMode;
 import org.elasticsearch.xpack.esql.EsqlIllegalArgumentException;
 import org.elasticsearch.xpack.esql.core.expression.Alias;
 import org.elasticsearch.xpack.esql.core.expression.Attribute;
@@ -19,6 +20,7 @@
 import org.elasticsearch.xpack.esql.core.util.Holder;
 import org.elasticsearch.xpack.esql.expression.function.aggregate.AggregateFunction;
 import org.elasticsearch.xpack.esql.expression.function.aggregate.FromPartial;
+import org.elasticsearch.xpack.esql.expression.function.aggregate.Rate;
 import org.elasticsearch.xpack.esql.expression.function.aggregate.TimeSeriesAggregateFunction;
 import org.elasticsearch.xpack.esql.expression.function.aggregate.ToPartial;
 import org.elasticsearch.xpack.esql.expression.function.aggregate.Values;
@@ -154,11 +156,15 @@ LogicalPlan translate(TimeSeriesAggregate aggregate) {
         Map<AggregateFunction, Alias> timeSeriesAggs = new HashMap<>();
         List<NamedExpression> firstPassAggs = new ArrayList<>();
         List<NamedExpression> secondPassAggs = new ArrayList<>();
+        Holder<Boolean> hasRateAggregates = new Holder<>(Boolean.FALSE);
         for (NamedExpression agg : aggregate.aggregates()) {
             if (agg instanceof Alias alias && alias.child() instanceof AggregateFunction af) {
                 Holder<Boolean> changed = new Holder<>(Boolean.FALSE);
                 Expression outerAgg = af.transformDown(TimeSeriesAggregateFunction.class, tsAgg -> {
                     changed.set(Boolean.TRUE);
+                    if (tsAgg instanceof Rate) {
+                        hasRateAggregates.set(Boolean.TRUE);
+                    }
                     AggregateFunction firstStageFn = tsAgg.perTimeSeriesAggregation();
                     Alias newAgg = timeSeriesAggs.computeIfAbsent(firstStageFn, k -> {
                         Alias firstStageAlias = new Alias(tsAgg.source(), agg.name(), firstStageFn);
@@ -231,16 +237,17 @@ LogicalPlan translate(TimeSeriesAggregate aggregate) {
             secondPassGroupings.add(new Alias(g.source(), g.name(), newFinalGroup.toAttribute(), g.id()));
         }
         LogicalPlan newChild = aggregate.child().transformUp(EsRelation.class, r -> {
+            IndexMode indexMode = hasRateAggregates.get() ? r.indexMode() : IndexMode.STANDARD;
             if (r.output().contains(tsid.get()) == false) {
                 return new EsRelation(
                     r.source(),
                     r.indexPattern(),
-                    r.indexMode(),
+                    indexMode,
                     r.indexNameWithModes(),
                     CollectionUtils.combine(r.output(), tsid.get())
                 );
             } else {
-                return r;
+                return new EsRelation(r.source(), r.indexPattern(), indexMode, r.indexNameWithModes(), r.output());
             }
         });
         final var firstPhase = new TimeSeriesAggregate(