Fix union types in CCS

docs/changelog/128111.yaml

@@ -0,0 +1,5 @@
+pr: 128111
+summary: Fix union types in CCS
+area: ES|QL
+type: bug
+issues: []

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

@@ -67,6 +67,12 @@ public static org.elasticsearch.Version remoteClusterVersion() {
         return prop != null ? org.elasticsearch.Version.fromString(prop) : org.elasticsearch.Version.CURRENT;
     }
 
+    public static org.elasticsearch.Version bwcVersion() {
+        org.elasticsearch.Version local = localClusterVersion();
+        org.elasticsearch.Version remote = remoteClusterVersion();
+        return local.before(remote) ? local : remote;
+    }
+
     private static Version distributionVersion(String key) {
         final String val = System.getProperty(key);
         return val != null ? Version.fromString(val) : Version.CURRENT;

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

@@ -76,6 +76,7 @@ public class MultiClusterSpecIT extends EsqlSpecTestCase {
 
     private static TestFeatureService remoteFeaturesService;
     private static RestClient remoteClusterClient;
+    private static DataLocation dataLocation = null;
 
     @ParametersFactory(argumentFormatting = "%2$s.%3$s")
     public static List<Object[]> readScriptSpec() throws Exception {
@@ -188,8 +189,9 @@ protected RestClient buildClient(Settings settings, HttpHost[] localHosts) throw
      */
     static RestClient twoClients(RestClient localClient, RestClient remoteClient) throws IOException {
         RestClient twoClients = mock(RestClient.class);
+        assertNotNull("data location was set", dataLocation);
         // write to a single cluster for now due to the precision of some functions such as avg and tests related to updates
-        final RestClient bulkClient = randomFrom(localClient, remoteClient);
+        final RestClient bulkClient = dataLocation == DataLocation.REMOTE_ONLY ? remoteClient : randomFrom(localClient, remoteClient);
         when(twoClients.performRequest(any())).then(invocation -> {
             Request request = invocation.getArgument(0);
             String endpoint = request.getEndpoint();
@@ -214,6 +216,11 @@ static RestClient twoClients(RestClient localClient, RestClient remoteClient) th
         return twoClients;
     }
 
+    enum DataLocation {
+        REMOTE_ONLY,
+        ANY_CLUSTER
+    }
+
     static Request[] cloneRequests(Request orig, int numClones) throws IOException {
         Request[] clones = new Request[numClones];
         for (int i = 0; i < clones.length; i++) {
@@ -238,26 +245,33 @@ static Request[] cloneRequests(Request orig, int numClones) throws IOException {
      * Convert FROM employees ... => FROM *:employees,employees
      */
     static CsvSpecReader.CsvTestCase convertToRemoteIndices(CsvSpecReader.CsvTestCase testCase) {
+        if (dataLocation == null) {
+            dataLocation = randomFrom(DataLocation.values());
+        }
         String query = testCase.query;
         String[] commands = query.split("\\|");
         String first = commands[0].trim();
         if (commands[0].toLowerCase(Locale.ROOT).startsWith("from")) {
             String[] parts = commands[0].split("(?i)metadata");
             assert parts.length >= 1 : parts;
             String fromStatement = parts[0];
-
-            String[] localIndices = fromStatement.substring("FROM ".length()).split(",");
-            String remoteIndices = Arrays.stream(localIndices)
-                .map(index -> "*:" + index.trim() + "," + index.trim())
-                .collect(Collectors.joining(","));
-            var newFrom = "FROM " + remoteIndices + " " + commands[0].substring(fromStatement.length());
+            String index = fromStatement.substring("FROM ".length());
+            if (canUseRemoteIndicesOnly() && randomBoolean()) {
+                index = remoteIndices(index);
+            } else {
+                index = index + "," + remoteIndices(index);
+            }
+            var newFrom = "FROM " + index + " " + commands[0].substring(fromStatement.length());
             testCase.query = newFrom + query.substring(first.length());
         }
         if (commands[0].toLowerCase(Locale.ROOT).startsWith("ts ")) {
             String[] parts = commands[0].split("\\s+");
             assert parts.length >= 2 : commands[0];
-            String[] indices = parts[1].split(",");
-            parts[1] = Arrays.stream(indices).map(index -> "*:" + index + "," + index).collect(Collectors.joining(","));
+            if (canUseRemoteIndicesOnly() && randomBoolean()) {
+                parts[1] = remoteIndices(parts[1]);
+            } else {
+                parts[1] = parts[1] + "," + remoteIndices(parts[1]);
+            }
             String newNewMetrics = String.join(" ", parts);
             testCase.query = newNewMetrics + query.substring(first.length());
         }
@@ -274,6 +288,15 @@ static CsvSpecReader.CsvTestCase convertToRemoteIndices(CsvSpecReader.CsvTestCas
         return testCase;
     }
 
+    static String remoteIndices(String localIndices) {
+        String[] parts = localIndices.split(",");
+        return Arrays.stream(parts).map(index -> "*:" + index.trim()).collect(Collectors.joining(","));
+    }
+
+    static boolean canUseRemoteIndicesOnly() {
+        return dataLocation == DataLocation.REMOTE_ONLY && Clusters.bwcVersion().onOrAfter(Version.V_9_1_0);
+    }
+
     static boolean hasIndexMetadata(String query) {
         String[] commands = query.split("\\|");
         if (commands[0].trim().toLowerCase(Locale.ROOT).startsWith("from")) {

x-pack/plugin/esql/src/internalClusterTest/java/org/elasticsearch/xpack/esql/action/CrossClusterQueryIT.java

@@ -991,4 +991,28 @@ void populateRemoteIndicesFail(String clusterAlias, String indexName, int numSha
         remoteClient.admin().indices().prepareRefresh(indexName).get();
     }
 
+    public void testMultiTypes() throws Exception {
+        Client remoteClient = client(REMOTE_CLUSTER_1);
+        int totalDocs = 0;
+        for (String type : List.of("integer", "long")) {
+            String index = "conflict-index-" + type;
+            assertAcked(remoteClient.admin().indices().prepareCreate(index).setMapping("port", "type=" + type));
+            int numDocs = between(1, 10);
+            for (int i = 0; i < numDocs; i++) {
+                remoteClient.prepareIndex(index).setId(Integer.toString(i)).setSource("port", i).get();
+            }
+            remoteClient.admin().indices().prepareRefresh(index).get();
+            totalDocs += numDocs;
+        }
+        for (String castFunction : List.of("TO_LONG", "TO_INT")) {
+            EsqlQueryRequest request = new EsqlQueryRequest();
+            request.query("FROM *:conflict-index-* | EVAL port=" + castFunction + "(port) | WHERE port is NOT NULL | STATS COUNT(port)");
+            try (EsqlQueryResponse resp = runQuery(request)) {
+                List<List<Object>> values = getValuesList(resp);
+                assertThat(values, hasSize(1));
+                assertThat(values.get(0), hasSize(1));
+                assertThat(values.get(0).get(0), equalTo((long) totalDocs));
+            }
+        }
+    }
 }

x-pack/plugin/esql/src/main/java/org/elasticsearch/xpack/esql/planner/EsPhysicalOperationProviders.java

@@ -157,7 +157,8 @@ private BlockLoader getBlockLoaderFor(int shardId, Attribute attr, MappedFieldTy
         BlockLoader blockLoader = shardContext.blockLoader(getFieldName(attr), isUnsupported, fieldExtractPreference);
         MultiTypeEsField unionTypes = findUnionTypes(attr);
         if (unionTypes != null) {
-            String indexName = shardContext.ctx.index().getName();
+            // Use the fully qualified name `cluster:index-name` because multiple types are resolved on coordinator with the cluster prefix
+            String indexName = shardContext.ctx.getFullyQualifiedIndex().getName();
             Expression conversion = unionTypes.getConversionExpressionForIndex(indexName);
             return conversion == null
                 ? BlockLoader.CONSTANT_NULLS