ESQL: Skip lookup fields when eliminating missing fields (elastic#118658)

We do not have SearchStats for fields from lookup indices. And unfortunately, these are hard to obtain.

For now, just do not apply ReplaceMissingFieldWithNull to fields coming from an index used in LOOKUP JOIN. These are identified via their indexmode.

Author: alex-spies

x-pack/plugin/esql/qa/server/mixed-cluster/src/javaRestTest/java/org/elasticsearch/xpack/esql/qa/mixed/MixedClusterEsqlSpecIT.java

@@ -21,7 +21,7 @@
 import java.util.List;
 
 import static org.elasticsearch.xpack.esql.CsvTestUtils.isEnabled;
-import static org.elasticsearch.xpack.esql.action.EsqlCapabilities.Cap.JOIN_LOOKUP_V6;
+import static org.elasticsearch.xpack.esql.action.EsqlCapabilities.Cap.JOIN_LOOKUP_V7;
 import static org.elasticsearch.xpack.esql.qa.rest.EsqlSpecTestCase.Mode.ASYNC;
 
 public class MixedClusterEsqlSpecIT extends EsqlSpecTestCase {
@@ -96,7 +96,7 @@ protected boolean supportsInferenceTestService() {
 
     @Override
     protected boolean supportsIndexModeLookup() throws IOException {
-        return hasCapabilities(List.of(JOIN_LOOKUP_V6.capabilityName()));
+        return hasCapabilities(List.of(JOIN_LOOKUP_V7.capabilityName()));
     }
 
     @Override

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

@@ -48,7 +48,7 @@
 import static org.elasticsearch.xpack.esql.EsqlTestUtils.classpathResources;
 import static org.elasticsearch.xpack.esql.action.EsqlCapabilities.Cap.INLINESTATS;
 import static org.elasticsearch.xpack.esql.action.EsqlCapabilities.Cap.INLINESTATS_V2;
-import static org.elasticsearch.xpack.esql.action.EsqlCapabilities.Cap.JOIN_LOOKUP_V6;
+import static org.elasticsearch.xpack.esql.action.EsqlCapabilities.Cap.JOIN_LOOKUP_V7;
 import static org.elasticsearch.xpack.esql.action.EsqlCapabilities.Cap.JOIN_PLANNING_V1;
 import static org.elasticsearch.xpack.esql.action.EsqlCapabilities.Cap.METADATA_FIELDS_REMOTE_TEST;
 import static org.elasticsearch.xpack.esql.qa.rest.EsqlSpecTestCase.Mode.SYNC;
@@ -124,7 +124,7 @@ protected void shouldSkipTest(String testName) throws IOException {
         assumeFalse("INLINESTATS not yet supported in CCS", testCase.requiredCapabilities.contains(INLINESTATS.capabilityName()));
         assumeFalse("INLINESTATS not yet supported in CCS", testCase.requiredCapabilities.contains(INLINESTATS_V2.capabilityName()));
         assumeFalse("INLINESTATS not yet supported in CCS", testCase.requiredCapabilities.contains(JOIN_PLANNING_V1.capabilityName()));
-        assumeFalse("LOOKUP JOIN not yet supported in CCS", testCase.requiredCapabilities.contains(JOIN_LOOKUP_V6.capabilityName()));
+        assumeFalse("LOOKUP JOIN not yet supported in CCS", testCase.requiredCapabilities.contains(JOIN_LOOKUP_V7.capabilityName()));
     }
 
     private TestFeatureService remoteFeaturesService() throws IOException {
@@ -283,8 +283,8 @@ protected boolean supportsInferenceTestService() {
 
     @Override
     protected boolean supportsIndexModeLookup() throws IOException {
-        // CCS does not yet support JOIN_LOOKUP_V6 and clusters falsely report they have this capability
-        // return hasCapabilities(List.of(JOIN_LOOKUP_V6.capabilityName()));
+        // CCS does not yet support JOIN_LOOKUP_V7 and clusters falsely report they have this capability
+        // return hasCapabilities(List.of(JOIN_LOOKUP_V7.capabilityName()));
         return false;
     }
 }

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

@@ -221,7 +221,7 @@ public void testIndicesDontExist() throws IOException {
         assertThat(e.getMessage(), containsString("index_not_found_exception"));
         assertThat(e.getMessage(), containsString("no such index [foo]"));
 
-        if (EsqlCapabilities.Cap.JOIN_LOOKUP_V6.isEnabled()) {
+        if (EsqlCapabilities.Cap.JOIN_LOOKUP_V7.isEnabled()) {
             e = expectThrows(
                 ResponseException.class,
                 () -> runEsql(timestampFilter("gte", "2020-01-01").query("FROM test1 | LOOKUP JOIN foo ON id1"))