ESQL: Views prototype

Initial work on getting views integrated with ES|QL
* Access views within FROM command
* Add csv-spec tests for non-branching and branching views
* Get CsvTests working on views
* Updated command-line CsvTestDataLoader for views, and multiple runs

Author: craigtaverner

x-pack/plugin/esql/qa/server/multi-clusters/src/javaRestTest/java/org/elasticsearch/xpack/esql/ccq/MultiClusterSpecIT.java

@@ -57,6 +57,7 @@
 import static org.elasticsearch.xpack.esql.action.EsqlCapabilities.Cap.METADATA_FIELDS_REMOTE_TEST;
 import static org.elasticsearch.xpack.esql.action.EsqlCapabilities.Cap.SUBQUERY_IN_FROM_COMMAND;
 import static org.elasticsearch.xpack.esql.action.EsqlCapabilities.Cap.UNMAPPED_FIELDS;
+import static org.elasticsearch.xpack.esql.action.EsqlCapabilities.Cap.VIEWS_WITH_NO_BRANCHING;
 import static org.elasticsearch.xpack.esql.qa.rest.RestEsqlTestCase.hasCapabilities;
 import static org.mockito.ArgumentMatchers.any;
 import static org.mockito.Mockito.doAnswer;
@@ -174,6 +175,7 @@ protected void shouldSkipTest(String testName) throws IOException {
             "Subqueries in FROM command not yet supported in CCS",
             testCase.requiredCapabilities.contains(SUBQUERY_IN_FROM_COMMAND.capabilityName())
         );
+        assumeFalse("VIEWS not yet supported in CCS", testCase.requiredCapabilities.contains(VIEWS_WITH_NO_BRANCHING.capabilityName()));
     }
 
     private TestFeatureService remoteFeaturesService() throws IOException {

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

@@ -76,7 +76,9 @@
 import static org.elasticsearch.xpack.esql.CsvTestUtils.loadCsvSpecValues;
 import static org.elasticsearch.xpack.esql.CsvTestsDataLoader.createInferenceEndpoints;
 import static org.elasticsearch.xpack.esql.CsvTestsDataLoader.deleteInferenceEndpoints;
+import static org.elasticsearch.xpack.esql.CsvTestsDataLoader.deleteViews;
 import static org.elasticsearch.xpack.esql.CsvTestsDataLoader.loadDataSetIntoEs;
+import static org.elasticsearch.xpack.esql.CsvTestsDataLoader.loadViewsIntoEs;
 import static org.elasticsearch.xpack.esql.EsqlTestUtils.classpathResources;
 import static org.elasticsearch.xpack.esql.action.EsqlCapabilities.Cap.COMPLETION;
 import static org.elasticsearch.xpack.esql.action.EsqlCapabilities.Cap.KNN_FUNCTION_V5;
@@ -103,6 +105,7 @@ public abstract class EsqlSpecTestCase extends ESRestTestCase {
     protected final String instructions;
     protected final Mode mode;
     protected static Boolean supportsTook;
+    protected static Boolean supportsViews;
 
     @ParametersFactory(argumentFormatting = "csv-spec:%2$s.%3$s")
     public static List<Object[]> readScriptSpec() throws Exception {
@@ -168,6 +171,7 @@ private synchronized void reset() {
     }
 
     private static final Protected INGEST = new Protected();
+    private static final Protected VIEWS = new Protected();
     protected static boolean testClustersOk = true;
 
     @Before
@@ -188,6 +192,13 @@ public void setup() {
             );
             return null;
         });
+        // Views can be created before or after ingest, since index resolution is currently only done on the combined query
+        VIEWS.protectedBlock(() -> {
+            if (supportsViews()) {
+                loadViewsIntoEs(adminClient());
+            }
+            return null;
+        });
     }
 
     @AfterClass
@@ -204,6 +215,8 @@ public static void wipeTestData() throws IOException {
             }
         }
         INGEST.reset();
+        deleteViews(adminClient());
+        VIEWS.reset();
         deleteInferenceEndpoints(adminClient());
     }
 
@@ -548,6 +561,13 @@ protected boolean supportsTook() throws IOException {
         return supportsTook;
     }
 
+    protected boolean supportsViews() {
+        if (supportsViews == null) {
+            supportsViews = hasCapabilities(adminClient(), List.of("views_with_no_branching"));
+        }
+        return supportsViews;
+    }
+
     private String tookKey(long took) {
         if (took < 10) {
             return "lt_10ms";

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

@@ -62,6 +62,11 @@ protected void shouldSkipTest(String testName) throws IOException {
 
         assumeFalse("Tests using PROMQL are not supported for now", testCase.requiredCapabilities.contains(PROMQL_V0.capabilityName()));
 
+        assumeFalse(
+            "Tests using VIEWS not supported for now (until we merge VIEWS and Subqueries/FORK including branch merging)",
+            testCase.requiredCapabilities.contains(VIEWS_WITH_BRANCHING.capabilityName())
+        );
+
         assumeTrue("Cluster needs to support FORK", hasCapabilities(adminClient(), List.of(FORK_V9.capabilityName())));
     }
 }