rename Metrics to TimeSeries and add a few more test cases and comments

Author: limotova

x-pack/plugin/esql/qa/server/src/main/java/org/elasticsearch/xpack/esql/qa/rest/generative/EsqlQueryGenerator.java

@@ -19,14 +19,14 @@
 import org.elasticsearch.xpack.esql.qa.rest.generative.command.pipe.KeepGenerator;
 import org.elasticsearch.xpack.esql.qa.rest.generative.command.pipe.LimitGenerator;
 import org.elasticsearch.xpack.esql.qa.rest.generative.command.pipe.LookupJoinGenerator;
-import org.elasticsearch.xpack.esql.qa.rest.generative.command.pipe.MetricsStatsGenerator;
+import org.elasticsearch.xpack.esql.qa.rest.generative.command.pipe.TimeSeriesStatsGenerator;
 import org.elasticsearch.xpack.esql.qa.rest.generative.command.pipe.MvExpandGenerator;
 import org.elasticsearch.xpack.esql.qa.rest.generative.command.pipe.RenameGenerator;
 import org.elasticsearch.xpack.esql.qa.rest.generative.command.pipe.SortGenerator;
 import org.elasticsearch.xpack.esql.qa.rest.generative.command.pipe.StatsGenerator;
 import org.elasticsearch.xpack.esql.qa.rest.generative.command.pipe.WhereGenerator;
 import org.elasticsearch.xpack.esql.qa.rest.generative.command.source.FromGenerator;
-import org.elasticsearch.xpack.esql.qa.rest.generative.command.source.MetricGenerator;
+import org.elasticsearch.xpack.esql.qa.rest.generative.command.source.TimeSeriesGenerator;
 
 import java.util.List;
 import java.util.Set;
@@ -56,7 +56,7 @@ public record QueryExecuted(String query, int depth, List<Column> outputSchema,
     /**
      * Commands at the beginning of queries that begin queries on time series indices, eg. TS
      */
-    static List<CommandGenerator> TIME_SERIES_SOURCE_COMMANDS = List.of(MetricGenerator.INSTANCE);
+    static List<CommandGenerator> TIME_SERIES_SOURCE_COMMANDS = List.of(TimeSeriesGenerator.INSTANCE);
 
     /**
      * These are downstream commands, ie. that cannot appear as the first command in a query
@@ -90,7 +90,7 @@ public record QueryExecuted(String query, int depth, List<Column> outputSchema,
         KeepGenerator.INSTANCE,
         LimitGenerator.INSTANCE,
         LookupJoinGenerator.INSTANCE,
-        MetricsStatsGenerator.INSTANCE,
+        TimeSeriesStatsGenerator.INSTANCE,
         MvExpandGenerator.INSTANCE,
         RenameGenerator.INSTANCE,
         SortGenerator.INSTANCE,
@@ -262,10 +262,12 @@ public static String metricsAgg(List<Column> previousOutput) {
                 if (numericPlusAggMetricFieldName == null) {
                     yield null;
                 }
-                yield switch ((randomIntBetween(0, 3))) {
+                yield switch ((randomIntBetween(0, 5))) {
                     case 0 -> "max_over_time(" + numericPlusAggMetricFieldName + ")";
                     case 1 -> "min_over_time(" + numericPlusAggMetricFieldName + ")";
                     case 2 -> "sum_over_time(" + numericPlusAggMetricFieldName + ")";
+                    case 3 -> "present_over_time(" + numericPlusAggMetricFieldName + ")";
+                    case 4 -> "count_over_time(" + numericPlusAggMetricFieldName + ")";
                     default -> "avg_over_time(" + numericPlusAggMetricFieldName + ")";
                 };
             }
@@ -279,7 +281,8 @@ yield switch ((randomIntBetween(0, 3))) {
             }
             case 2 -> {
                 // numerics except aggregate_metric_double
-                // TODO: move to case 0 when support for aggregate_metric_double is added to these functions
+                // TODO: add to case 0 when support for aggregate_metric_double is added to these functions
+                // TODO: add to case 1 when support for counters is added
                 String numericFieldName = randomNumericField(previousOutput);
                 if (numericFieldName == null) {
                     yield null;

x-pack/plugin/esql/qa/server/src/main/java/org/elasticsearch/xpack/esql/qa/rest/generative/command/pipe/MetricsStatsGenerator.java renamed to x-pack/plugin/esql/qa/server/src/main/java/org/elasticsearch/xpack/esql/qa/rest/generative/command/pipe/TimeSeriesStatsGenerator.java

@@ -18,10 +18,10 @@
 import static org.elasticsearch.test.ESTestCase.randomIntBetween;
 import static org.elasticsearch.xpack.esql.qa.rest.generative.EsqlQueryGenerator.randomDateField;
 
-public class MetricsStatsGenerator implements CommandGenerator {
+public class TimeSeriesStatsGenerator implements CommandGenerator {
 
     public static final String STATS = "stats";
-    public static final CommandGenerator INSTANCE = new MetricsStatsGenerator();
+    public static final CommandGenerator INSTANCE = new TimeSeriesStatsGenerator();
 
     @Override
     public CommandDescription generate(
@@ -31,8 +31,9 @@ public CommandDescription generate(
     ) {
         // generates stats in the form of:
         // `STATS some_aggregation(some_field) by optional_grouping_field, non_optional = bucket(time_field, 5minute)`
-        // where `some_aggregation` can be a time series aggregation, or a regular aggregation
-        // There is a variable number of aggregations per command
+        // where `some_aggregation` can be a time series aggregation in the form of agg1(agg2_over_time(some_field)),
+        // or a regular aggregation.
+        // There is a variable number of aggregations per pipe
 
         List<EsqlQueryGenerator.Column> nonNull = previousOutput.stream()
             .filter(EsqlQueryGenerator::fieldCanBeUsed)

x-pack/plugin/esql/qa/server/src/main/java/org/elasticsearch/xpack/esql/qa/rest/generative/command/source/MetricGenerator.java renamed to x-pack/plugin/esql/qa/server/src/main/java/org/elasticsearch/xpack/esql/qa/rest/generative/command/source/TimeSeriesGenerator.java

@@ -16,9 +16,9 @@
 import static org.elasticsearch.test.ESTestCase.randomIntBetween;
 import static org.elasticsearch.xpack.esql.qa.rest.generative.EsqlQueryGenerator.indexPattern;
 
-public class MetricGenerator implements CommandGenerator {
+public class TimeSeriesGenerator implements CommandGenerator {
 
-    public static final MetricGenerator INSTANCE = new MetricGenerator();
+    public static final TimeSeriesGenerator INSTANCE = new TimeSeriesGenerator();
 
     @Override
     public CommandDescription generate(