Disallow CCS with lookup join

docs/changelog/120277.yaml

@@ -0,0 +1,5 @@
+pr: 120277
+summary: Disallow CCS with lookup join
+area: ES|QL
+type: enhancement
+issues: []

x-pack/plugin/esql/src/main/java/org/elasticsearch/xpack/esql/parser/LogicalPlanBuilder.java

@@ -15,6 +15,7 @@
 import org.elasticsearch.dissect.DissectException;
 import org.elasticsearch.dissect.DissectParser;
 import org.elasticsearch.index.IndexMode;
+import org.elasticsearch.transport.RemoteClusterAware;
 import org.elasticsearch.xpack.esql.VerificationException;
 import org.elasticsearch.xpack.esql.common.Failure;
 import org.elasticsearch.xpack.esql.core.expression.Alias;
@@ -523,9 +524,15 @@ public PlanFactory visitJoinCommand(EsqlBaseParser.JoinCommandContext ctx) {
         }
 
         var target = ctx.joinTarget();
+        var rightPattern = visitIdentifier(target.index);
+
+        if (RemoteClusterAware.isRemoteIndexName(rightPattern)) {
+            throw new ParsingException(source(target), "LOOKUP JOIN does not support remote cluster indices [{}]", rightPattern);
+        }
+
         UnresolvedRelation right = new UnresolvedRelation(
             source(target),
-            new TableIdentifier(source(target.index), null, visitIdentifier(target.index)),
+            new TableIdentifier(source(target.index), null, rightPattern),
             false,
             emptyList(),
             IndexMode.LOOKUP,
@@ -552,6 +559,18 @@ public PlanFactory visitJoinCommand(EsqlBaseParser.JoinCommandContext ctx) {
             throw new ParsingException(source, "JOIN ON clause only supports one field at the moment, found [{}]", matchFieldsCount);
         }
 
-        return p -> new LookupJoin(source, p, right, joinFields);
+        return p -> {
+            p.forEachUp(UnresolvedRelation.class, r -> {
+                if (RemoteClusterAware.isRemoteIndexName(r.table().index())) {
+                    throw new ParsingException(
+                        source(target),
+                        "LOOKUP JOIN does not support remote cluster indices [{}]",
+                        r.table().index()
+                    );
+                }
+            });
+
+            return new LookupJoin(source, p, right, joinFields);
+        };
     }
 }

x-pack/plugin/esql/src/test/java/org/elasticsearch/xpack/esql/parser/StatementParserTests.java

@@ -300,18 +300,18 @@ public void testStatsWithoutGroups() {
         );
     }
 
-    public void testStatsWithoutAggs() throws Exception {
+    public void testStatsWithoutAggs() {
         assertEquals(
             new Aggregate(EMPTY, PROCESSING_CMD_INPUT, Aggregate.AggregateType.STANDARD, List.of(attribute("a")), List.of(attribute("a"))),
             processingCommand("stats by a")
         );
     }
 
-    public void testStatsWithoutAggsOrGroup() throws Exception {
+    public void testStatsWithoutAggsOrGroup() {
         expectError("from text | stats", "At least one aggregation or grouping expression required in [stats]");
     }
 
-    public void testAggsWithGroupKeyAsAgg() throws Exception {
+    public void testAggsWithGroupKeyAsAgg() {
         var queries = new String[] { """
             row a = 1, b = 2
             | stats a by a
@@ -332,7 +332,7 @@ public void testAggsWithGroupKeyAsAgg() throws Exception {
         }
     }
 
-    public void testStatsWithGroupKeyAndAggFilter() throws Exception {
+    public void testStatsWithGroupKeyAndAggFilter() {
         var a = attribute("a");
         var f = new UnresolvedFunction(EMPTY, "min", DEFAULT, List.of(a));
         var filter = new Alias(EMPTY, "min(a) where a > 1", new FilteredExpression(EMPTY, f, new GreaterThan(EMPTY, a, integer(1))));
@@ -342,7 +342,7 @@ public void testStatsWithGroupKeyAndAggFilter() throws Exception {
         );
     }
 
-    public void testStatsWithGroupKeyAndMixedAggAndFilter() throws Exception {
+    public void testStatsWithGroupKeyAndMixedAggAndFilter() {
         var a = attribute("a");
         var min = new UnresolvedFunction(EMPTY, "min", DEFAULT, List.of(a));
         var max = new UnresolvedFunction(EMPTY, "max", DEFAULT, List.of(a));
@@ -377,7 +377,7 @@ public void testStatsWithGroupKeyAndMixedAggAndFilter() throws Exception {
         );
     }
 
-    public void testStatsWithoutGroupKeyMixedAggAndFilter() throws Exception {
+    public void testStatsWithoutGroupKeyMixedAggAndFilter() {
         var a = attribute("a");
         var f = new UnresolvedFunction(EMPTY, "min", DEFAULT, List.of(a));
         var filter = new Alias(EMPTY, "min(a) where a > 1", new FilteredExpression(EMPTY, f, new GreaterThan(EMPTY, a, integer(1))));
@@ -2060,41 +2060,41 @@ private void assertStringAsLookupIndexPattern(String string, String statement) {
         assertThat(tableName.fold(FoldContext.small()), equalTo(string));
     }
 
-    public void testIdPatternUnquoted() throws Exception {
+    public void testIdPatternUnquoted() {
         var string = "regularString";
         assertThat(breakIntoFragments(string), contains(string));
     }
 
-    public void testIdPatternQuoted() throws Exception {
+    public void testIdPatternQuoted() {
         var string = "`escaped string`";
         assertThat(breakIntoFragments(string), contains(string));
     }
 
-    public void testIdPatternQuotedWithDoubleBackticks() throws Exception {
+    public void testIdPatternQuotedWithDoubleBackticks() {
         var string = "`escaped``string`";
         assertThat(breakIntoFragments(string), contains(string));
     }
 
-    public void testIdPatternUnquotedAndQuoted() throws Exception {
+    public void testIdPatternUnquotedAndQuoted() {
         var string = "this`is`a`mix`of`ids`";
         assertThat(breakIntoFragments(string), contains("this", "`is`", "a", "`mix`", "of", "`ids`"));
     }
 
-    public void testIdPatternQuotedTraling() throws Exception {
+    public void testIdPatternQuotedTraling() {
         var string = "`foo`*";
         assertThat(breakIntoFragments(string), contains("`foo`", "*"));
     }
 
-    public void testIdPatternWithDoubleQuotedStrings() throws Exception {
+    public void testIdPatternWithDoubleQuotedStrings() {
         var string = "`this``is`a`quoted `` string``with`backticks";
         assertThat(breakIntoFragments(string), contains("`this``is`", "a", "`quoted `` string``with`", "backticks"));
     }
 
-    public void testSpaceNotAllowedInIdPattern() throws Exception {
+    public void testSpaceNotAllowedInIdPattern() {
         expectError("ROW a = 1| RENAME a AS this is `not okay`", "mismatched input 'is' expecting {<EOF>, '|', ',', '.'}");
     }
 
-    public void testSpaceNotAllowedInIdPatternKeep() throws Exception {
+    public void testSpaceNotAllowedInIdPatternKeep() {
         expectError("ROW a = 1, b = 1| KEEP a b", "extraneous input 'b'");
     }
 
@@ -2939,4 +2939,14 @@ public void testNamedFunctionArgumentWithUnsupportedNamedParameterTypes() {
             );
         }
     }
+
+    public void testRemoteLookupJoin() {
+        expectError("FROM remote:left | LOOKUP JOIN right ON field", "LOOKUP JOIN does not support remote cluster indices [remote:left]");
+        expectError(
+            "FROM  left | LOOKUP JOIN `remote:right` ON field",
+            "LOOKUP JOIN does not support remote cluster indices [remote:right]"
+        );
+        // TODO ES-10559 this should be replaced with a proper error message once grammar allows indexPattern as joinTarget
+        expectError("FROM my-index | LOOKUP JOIN remote:languages_lookup ON language_code", "line 1:35: token recognition error at: ':'");
+    }
 }