Enable CSS support for inference commands.

Author: afoucret

x-pack/plugin/esql/src/main/java/org/elasticsearch/xpack/esql/action/EsqlCapabilities.java

@@ -1734,6 +1734,11 @@ public enum Cap {
          */
         TOP_SNIPPETS_FUNCTION(Build.current().isSnapshot()),
 
+        /**
+         * Support for inference in cross-cluster search (CCS)
+         */
+        INFERENCE_COMMANDS_CCS_SUPPORT,
+
         // Last capability should still have a comma for fewer merge conflicts when adding new ones :)
         // This comment prevents the semicolon from being on the previous capability when Spotless formats the file.
         ;

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

@@ -1126,7 +1126,10 @@ public PlanFactory visitRerankCommand(EsqlBaseParser.RerankCommandContext ctx) {
         Literal rowLimit = Literal.integer(source, context.inferenceSettings().rerankRowLimit());
 
         return p -> {
-            checkForRemoteClusters(p, source, "RERANK");
+            if (EsqlCapabilities.Cap.INFERENCE_COMMANDS_CCS_SUPPORT.isEnabled() == false) {
+                checkForRemoteClusters(p, source, "RERANK");
+            }
+
             return applyRerankOptions(
                 new Rerank(source, p, rowLimit, queryText, rerankFields, scoreAttribute),
                 ctx.commandNamedParameters()
@@ -1177,7 +1180,9 @@ public PlanFactory visitCompletionCommand(EsqlBaseParser.CompletionCommandContex
         Literal rowLimit = Literal.integer(source, context.inferenceSettings().completionRowLimit());
 
         return p -> {
-            checkForRemoteClusters(p, source, "COMPLETION");
+            if (EsqlCapabilities.Cap.INFERENCE_COMMANDS_CCS_SUPPORT.isEnabled() == false) {
+                checkForRemoteClusters(p, source, "COMPLETION");
+            }
             return applyCompletionOptions(new Completion(source, p, rowLimit, prompt, targetField), ctx.commandNamedParameters());
         };
     }

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

@@ -3818,12 +3818,6 @@ public void testInvalidRerank() {
         expectError("FROM foo* | RERANK ON title WITH inferenceId", "line 1:20: extraneous input 'ON' expecting {QUOTED_STRING");
         expectError("FROM foo* | RERANK \"query text\" WITH inferenceId", "line 1:33: mismatched input 'WITH' expecting 'on'");
 
-        var fromPatterns = randomIndexPatterns(CROSS_CLUSTER);
-        expectError(
-            "FROM " + fromPatterns + " | RERANK \"query text\" ON title WITH { \"inference_id\" : \"inference_id\" }",
-            "invalid index pattern [" + unquoteIndexPattern(fromPatterns) + "], remote clusters are not supported with RERANK"
-        );
-
         expectError(
             "FROM foo* | RERANK \"query text\" ON title WITH { \"inference_id\": { \"a\": 123 } }",
             "Option [inference_id] must be a valid string, found [{ \"a\": 123 }]"
@@ -3937,12 +3931,6 @@ public void testInvalidCompletion() {
 
         expectError("FROM foo* | COMPLETION completion=prompt WITH", "ine 1:46: mismatched input '<EOF>' expecting '{'");
 
-        var fromPatterns = randomIndexPatterns(CROSS_CLUSTER);
-        expectError(
-            "FROM " + fromPatterns + " | COMPLETION prompt_field WITH { \"inference_id\" : \"inference_id\" }",
-            "invalid index pattern [" + unquoteIndexPattern(fromPatterns) + "], remote clusters are not supported with COMPLETION"
-        );
-
         expectError(
             "FROM foo* | COMPLETION prompt WITH { \"inference_id\": { \"a\": 123 } }",
             "line 1:54: Option [inference_id] must be a valid string, found [{ \"a\": 123 }]"