ES|QL: Add generator for INLINE STATS (#135685)

Author: luigidellaquila

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

@@ -66,6 +66,7 @@ public abstract class GenerativeRestTest extends ESRestTestCase implements Query
         "The incoming YAML document exceeds the limit:", // still to investigate, but it seems to be specific to the test framework
         "Data too large", // Circuit breaker exceptions eg. https://github.com/elastic/elasticsearch/issues/130072
         "optimized incorrectly due to missing references", // https://github.com/elastic/elasticsearch/issues/131509
+        "can't build page out of released blocks", // https://github.com/elastic/elasticsearch/issues/135679
 
         // Awaiting fixes for correctness
         "Expecting at most \\[.*\\] columns, got \\[.*\\]", // https://github.com/elastic/elasticsearch/issues/129561

x-pack/plugin/esql/qa/testFixtures/src/main/java/org/elasticsearch/xpack/esql/generator/EsqlQueryGenerator.java

@@ -16,6 +16,7 @@
 import org.elasticsearch.xpack.esql.generator.command.pipe.EvalGenerator;
 import org.elasticsearch.xpack.esql.generator.command.pipe.ForkGenerator;
 import org.elasticsearch.xpack.esql.generator.command.pipe.GrokGenerator;
+import org.elasticsearch.xpack.esql.generator.command.pipe.InlineStatsGenerator;
 import org.elasticsearch.xpack.esql.generator.command.pipe.KeepGenerator;
 import org.elasticsearch.xpack.esql.generator.command.pipe.LimitGenerator;
 import org.elasticsearch.xpack.esql.generator.command.pipe.LookupJoinGenerator;
@@ -67,6 +68,7 @@ public class EsqlQueryGenerator {
         ForkGenerator.INSTANCE,
         GrokGenerator.INSTANCE,
         KeepGenerator.INSTANCE,
+        InlineStatsGenerator.INSTANCE,
         LimitGenerator.INSTANCE,
         LookupJoinGenerator.INSTANCE,
         MvExpandGenerator.INSTANCE,

x-pack/plugin/esql/qa/testFixtures/src/main/java/org/elasticsearch/xpack/esql/generator/command/pipe/InlineStatsGenerator.java

@@ -0,0 +1,49 @@
+/*
+ * Copyright Elasticsearch B.V. and/or licensed to Elasticsearch B.V. under one
+ * or more contributor license agreements. Licensed under the Elastic License
+ * 2.0; you may not use this file except in compliance with the Elastic License
+ * 2.0.
+ */
+
+package org.elasticsearch.xpack.esql.generator.command.pipe;
+
+import org.elasticsearch.xpack.esql.generator.Column;
+import org.elasticsearch.xpack.esql.generator.command.CommandGenerator;
+
+import java.util.List;
+
+public class InlineStatsGenerator extends StatsGenerator {
+    public static final String INLINE_STATS = "inline stats";
+    public static final CommandGenerator INSTANCE = new InlineStatsGenerator();
+
+    @Override
+    public String commandName() {
+        return INLINE_STATS;
+    }
+
+    @Override
+    public ValidationResult validateOutput(
+        List<CommandDescription> previousCommands,
+        CommandDescription commandDescription,
+        List<Column> previousColumns,
+        List<List<Object>> previousOutput,
+        List<Column> columns,
+        List<List<Object>> output
+    ) {
+        if (commandDescription == EMPTY_DESCRIPTION) {
+            return VALIDATION_OK;
+        }
+
+        int prevCols = previousColumns.size();
+
+        if (previousColumns.stream().anyMatch(x -> x.name().equals("<all-fields-projected>"))) {
+            // known bug https://github.com/elastic/elasticsearch/issues/121741
+            prevCols--;
+        }
+
+        if (prevCols > columns.size()) {
+            return new ValidationResult(false, "Expecting at least [" + prevCols + "] columns, got [" + columns.size() + "]");
+        }
+        return VALIDATION_OK;
+    }
+}

x-pack/plugin/esql/qa/testFixtures/src/main/java/org/elasticsearch/xpack/esql/generator/command/pipe/StatsGenerator.java

@@ -24,6 +24,10 @@ public class StatsGenerator implements CommandGenerator {
     public static final String STATS = "stats";
     public static final CommandGenerator INSTANCE = new StatsGenerator();
 
+    public String commandName() {
+        return STATS;
+    }
+
     @Override
     public CommandDescription generate(
         List<CommandDescription> previousCommands,
@@ -38,7 +42,9 @@ public CommandDescription generate(
         if (nonNull.isEmpty()) {
             return EMPTY_DESCRIPTION;
         }
-        StringBuilder cmd = new StringBuilder(" | stats ");
+        StringBuilder cmd = new StringBuilder(" | ");
+        cmd.append(commandName());
+        cmd.append(" ");
         int nStats = randomIntBetween(1, 5);
         for (int i = 0; i < nStats; i++) {
             String name;
@@ -65,7 +71,7 @@ public CommandDescription generate(
                 cmd.append(" by " + col);
             }
         }
-        return new CommandDescription(STATS, this, cmd.toString(), Map.of());
+        return new CommandDescription(commandName(), this, cmd.toString(), Map.of());
     }
 
     @Override