ES|QL: add generative tests for CHANGE_POINT command

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

@@ -9,6 +9,7 @@
 
 import org.elasticsearch.xpack.esql.CsvTestsDataLoader;
 import org.elasticsearch.xpack.esql.qa.rest.generative.command.CommandGenerator;
+import org.elasticsearch.xpack.esql.qa.rest.generative.command.pipe.ChangePointGenerator;
 import org.elasticsearch.xpack.esql.qa.rest.generative.command.pipe.DissectGenerator;
 import org.elasticsearch.xpack.esql.qa.rest.generative.command.pipe.DropGenerator;
 import org.elasticsearch.xpack.esql.qa.rest.generative.command.pipe.EnrichGenerator;
@@ -49,6 +50,7 @@ public record QueryExecuted(String query, int depth, List<Column> outputSchema,
      * These are downstream commands, ie. that cannot appear as the first command in a query
      */
     static List<CommandGenerator> PIPE_COMMANDS = List.of(
+        ChangePointGenerator.INSTANCE,
         DissectGenerator.INSTANCE,
         DropGenerator.INSTANCE,
         EnrichGenerator.INSTANCE,
@@ -197,6 +199,10 @@ public static String randomNumericOrDateField(List<Column> previousOutput) {
         return randomName(previousOutput, Set.of("long", "integer", "double", "date"));
     }
 
+    public static String randomDateField(List<Column> previousOutput) {
+        return randomName(previousOutput, Set.of("date"));
+    }
+
     public static String randomNumericField(List<Column> previousOutput) {
         return randomName(previousOutput, Set.of("long", "integer", "double"));
     }
@@ -255,6 +261,22 @@ public static String constantExpression() {
 
     }
 
+    /**
+     * returns a random identifier or one of the existing names
+     */
+    public static String randomAttributeOrIdentifier(List<EsqlQueryGenerator.Column> previousOutput) {
+        String name;
+        if (randomBoolean()) {
+            name = EsqlQueryGenerator.randomIdentifier();
+        } else {
+            name = EsqlQueryGenerator.randomName(previousOutput);
+            if (name == null) {
+                name = EsqlQueryGenerator.randomIdentifier();
+            }
+        }
+        return name;
+    }
+
     public static String randomIdentifier() {
         // Let's create identifiers that are long enough to avoid collisions with reserved keywords.
         // There could be a smarter way (introspection on the lexer class?), but probably it's not worth the effort

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

@@ -10,6 +10,7 @@
 import org.elasticsearch.client.Request;
 import org.elasticsearch.client.ResponseException;
 import org.elasticsearch.test.rest.ESRestTestCase;
+import org.elasticsearch.xpack.esql.AssertWarnings;
 import org.elasticsearch.xpack.esql.CsvTestsDataLoader;
 import org.elasticsearch.xpack.esql.qa.rest.RestEsqlTestCase;
 import org.elasticsearch.xpack.esql.qa.rest.generative.command.CommandGenerator;
@@ -44,10 +45,6 @@ public abstract class GenerativeRestTest extends ESRestTestCase {
         "The field names are too complex to process", // field_caps problem
         "must be \\[any type except counter types\\]", // TODO refine the generation of count()
 
-        // warnings
-        "Field '.*' shadowed by field at line .*",
-        "evaluation of \\[.*\\] failed, treating result as null", // TODO investigate?
-
         // Awaiting fixes for query failure
         "Unknown column \\[<all-fields-projected>\\]", // https://github.com/elastic/elasticsearch/issues/121741,
         "Plan \\[ProjectExec\\[\\[<no-fields>.* optimized incorrectly due to missing references", // https://github.com/elastic/elasticsearch/issues/125866
@@ -99,10 +96,10 @@ public void test() throws IOException {
             EsqlQueryGenerator.QueryExecuted result = execute(command, 0);
             if (result.exception() != null) {
                 checkException(result);
-                break;
+                continue;
             }
             if (checkResults(List.of(), commandGenerator, desc, null, result).success() == false) {
-                break;
+                continue;
             }
             previousResult = result;
             previousCommands.add(desc);
@@ -168,7 +165,11 @@ private void checkException(EsqlQueryGenerator.QueryExecuted query) {
     @SuppressWarnings("unchecked")
     private EsqlQueryGenerator.QueryExecuted execute(String command, int depth) {
         try {
-            Map<String, Object> a = RestEsqlTestCase.runEsqlSync(new RestEsqlTestCase.RequestObjectBuilder().query(command).build());
+            Map<String, Object> a = RestEsqlTestCase.runEsql(
+                new RestEsqlTestCase.RequestObjectBuilder().query(command).build(),
+                new AssertWarnings.AllowedRegexes(List.of(Pattern.compile(".*"))),// we don't care about warnings
+                RestEsqlTestCase.Mode.SYNC
+            );
             List<EsqlQueryGenerator.Column> outputSchema = outputSchema(a);
             List<List<Object>> values = (List<List<Object>>) a.get("values");
             return new EsqlQueryGenerator.QueryExecuted(command, depth, outputSchema, values, null);

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

@@ -139,4 +139,22 @@ static ValidationResult expectSameColumns(List<EsqlQueryGenerator.Column> previo
 
         return VALIDATION_OK;
     }
+
+    /**
+     * The command doesn't have to produce LESS columns than the previous query
+     */
+    static ValidationResult expectAtLeastSameNumberOfColumns(
+        List<EsqlQueryGenerator.Column> previousColumns,
+        List<EsqlQueryGenerator.Column> columns
+    ) {
+        if (previousColumns.stream().anyMatch(x -> x.name().contains("<all-fields-projected>"))) {
+            return VALIDATION_OK; // known bug
+        }
+
+        if (previousColumns.size() > columns.size()) {
+            return new ValidationResult(false, "Expecting at least [" + previousColumns.size() + "] columns, got [" + columns.size() + "]");
+        }
+
+        return VALIDATION_OK;
+    }
 }

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

@@ -0,0 +1,55 @@
+/*
+ * 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.qa.rest.generative.command.pipe;
+
+import org.elasticsearch.xpack.esql.qa.rest.generative.EsqlQueryGenerator;
+import org.elasticsearch.xpack.esql.qa.rest.generative.command.CommandGenerator;
+
+import java.util.List;
+import java.util.Map;
+
+import static org.elasticsearch.xpack.esql.qa.rest.generative.EsqlQueryGenerator.randomAttributeOrIdentifier;
+
+public class ChangePointGenerator implements CommandGenerator {
+    public static final String CHANGE_POINT = "change_point";
+    public static final CommandGenerator INSTANCE = new ChangePointGenerator();
+
+    @Override
+    public CommandDescription generate(
+        List<CommandDescription> previousCommands,
+        List<EsqlQueryGenerator.Column> previousOutput,
+        QuerySchema schema
+    ) {
+        String timestampField = EsqlQueryGenerator.randomDateField(previousOutput);
+        String numericField = EsqlQueryGenerator.randomNumericField(previousOutput);
+        if (timestampField == null || numericField == null) {
+            return EMPTY_DESCRIPTION;
+        }
+        String alias1 = randomAttributeOrIdentifier(previousOutput);
+        String alias2 = randomAttributeOrIdentifier(previousOutput);
+        while (alias1.equals(alias2)) {
+            alias2 = randomAttributeOrIdentifier(previousOutput);
+        }
+
+        String cmd = " | CHANGE_POINT " + numericField + " ON " + timestampField + " AS " + alias1 + ", " + alias2;
+
+        return new CommandDescription(CHANGE_POINT, this, cmd, Map.of());
+    }
+
+    @Override
+    public ValidationResult validateOutput(
+        List<CommandDescription> previousCommands,
+        CommandDescription command,
+        List<EsqlQueryGenerator.Column> previousColumns,
+        List<List<Object>> previousOutput,
+        List<EsqlQueryGenerator.Column> columns,
+        List<List<Object>> output
+    ) {
+        return CommandGenerator.expectAtLeastSameNumberOfColumns(previousColumns, columns);
+    }
+}