ESQL: Fix wrong marking of a field as unmapped when indices shared the same mapping

Author: GalLalouche

x-pack/plugin/esql/src/main/java/org/elasticsearch/xpack/esql/session/IndexResolver.java

@@ -92,7 +92,6 @@ public void resolveAsMergedMapping(
 
     // public for testing only
     public static IndexResolution mergedMappings(String indexPattern, FieldCapabilitiesResponse fieldCapsResponse) {
-        var numberOfIndices = fieldCapsResponse.getIndexResponses().size();
         assert ThreadPool.assertCurrentThreadPool(ThreadPool.Names.SEARCH_COORDINATION); // too expensive to run this on a transport worker
         if (fieldCapsResponse.getIndexResponses().isEmpty()) {
             return IndexResolution.notFound(indexPattern);
@@ -143,8 +142,7 @@ public static IndexResolution mergedMappings(String indexPattern, FieldCapabilit
                 );
             fields.put(name, field);
 
-            var isPartiallyUnmapped = fcs.size() < numberOfIndices;
-            if (isPartiallyUnmapped) {
+            if (fieldCapsResponse.getIndexResponses().stream().allMatch(fcir -> fcir.get().containsKey(fullName)) == false) {
                 partiallyUnmappedFields.add(fullName);
             }
         }

x-pack/plugin/esql/src/test/java/org/elasticsearch/xpack/esql/analysis/AnalyzerTests.java

@@ -12,6 +12,7 @@
 import org.elasticsearch.action.fieldcaps.FieldCapabilitiesResponse;
 import org.elasticsearch.action.fieldcaps.IndexFieldCapabilities;
 import org.elasticsearch.action.fieldcaps.IndexFieldCapabilitiesBuilder;
+import org.elasticsearch.common.hash.MessageDigests;
 import org.elasticsearch.common.lucene.BytesRefs;
 import org.elasticsearch.common.settings.Settings;
 import org.elasticsearch.index.IndexMode;
@@ -3101,6 +3102,27 @@ public void testResolveInsist_multiIndexFieldPartiallyExistsWithMultiTypesNoKeyw
         assertThat(attr.unresolvedMessage(), is(expected));
     }
 
+    public void testResolveInsist_multiIndexSameMapping_fieldIsMapped() {
+        assumeTrue("Requires UNMAPPED FIELDS", EsqlCapabilities.Cap.UNMAPPED_FIELDS.isEnabled());
+
+        IndexResolution resolution = IndexResolver.mergedMappings(
+            "foo, bar",
+            new FieldCapabilitiesResponse(
+                List.of(
+                    fieldCapabilitiesIndexResponse("foo", messageResponseMap("long")),
+                    fieldCapabilitiesIndexResponse("bar", messageResponseMap("long"))
+                ),
+                List.of()
+            )
+        );
+        var plan = analyze("FROM foo, bar | INSIST_🐔 message", analyzer(resolution, TEST_VERIFIER));
+        var limit = as(plan, Limit.class);
+        var insist = as(limit.child(), Insist.class);
+        var attribute = (FieldAttribute) EsqlTestUtils.singleValue(insist.output());
+        assertThat(attribute.name(), is("message"));
+        assertThat(attribute.dataType(), is(DataType.LONG));
+    }
+
     public void testResolveInsist_multiIndexFieldPartiallyExistsWithMultiTypesWithKeyword_createsAnInvalidMappedField() {
         assumeTrue("Requires UNMAPPED FIELDS", EsqlCapabilities.Cap.UNMAPPED_FIELDS.isEnabled());
 
@@ -3531,7 +3553,8 @@ private static FieldCapabilitiesIndexResponse fieldCapabilitiesIndexResponse(
         String indexName,
         Map<String, IndexFieldCapabilities> fields
     ) {
-        return new FieldCapabilitiesIndexResponse(indexName, indexName, fields, false, IndexMode.STANDARD);
+        String indexMappingHash = new String(MessageDigests.sha256().digest(fields.toString().getBytes()));
+        return new FieldCapabilitiesIndexResponse(indexName, indexMappingHash, fields, false, IndexMode.STANDARD);
     }
 
     private static Map<String, IndexFieldCapabilities> messageResponseMap(String date) {