Remove legacy IndexResolver (elastic#109821)

Currently, we are using the legacy IndexResolver alongside the updated 
version to compare their outputs. While this approach helps in bug
detection, it adds to the maintenance burden, particularly when adding
new features to the field-caps API or the index resolver. This change
removes the legacy IndexResolver from the ESQL codebase.

x-pack/plugin/esql/src/main/java/org/elasticsearch/xpack/esql/enrich/EnrichPolicyResolver.java

@@ -37,11 +37,10 @@
 import org.elasticsearch.xpack.core.enrich.EnrichPolicy;
 import org.elasticsearch.xpack.esql.analysis.EnrichResolution;
 import org.elasticsearch.xpack.esql.core.index.EsIndex;
-import org.elasticsearch.xpack.esql.core.index.IndexResolver;
 import org.elasticsearch.xpack.esql.core.type.EsField;
 import org.elasticsearch.xpack.esql.core.util.StringUtils;
 import org.elasticsearch.xpack.esql.plan.logical.Enrich;
-import org.elasticsearch.xpack.esql.session.EsqlSession;
+import org.elasticsearch.xpack.esql.session.IndexResolver;
 import org.elasticsearch.xpack.esql.type.EsqlDataTypes;
 
 import java.io.IOException;
@@ -359,29 +358,22 @@ public void messageReceived(LookupRequest request, TransportChannel channel, Tas
                     }
                     try (ThreadContext.StoredContext ignored = threadContext.stashWithOrigin(ClientHelper.ENRICH_ORIGIN)) {
                         String indexName = EnrichPolicy.getBaseName(policyName);
-                        indexResolver.resolveAsMergedMapping(
-                            indexName,
-                            IndexResolver.ALL_FIELDS,
-                            false,
-                            Map.of(),
-                            refs.acquire(indexResult -> {
-                                if (indexResult.isValid() && indexResult.get().concreteIndices().size() == 1) {
-                                    EsIndex esIndex = indexResult.get();
-                                    var concreteIndices = Map.of(request.clusterAlias, Iterables.get(esIndex.concreteIndices(), 0));
-                                    var resolved = new ResolvedEnrichPolicy(
-                                        p.getMatchField(),
-                                        p.getType(),
-                                        p.getEnrichFields(),
-                                        concreteIndices,
-                                        esIndex.mapping()
-                                    );
-                                    resolvedPolices.put(policyName, resolved);
-                                } else {
-                                    failures.put(policyName, indexResult.toString());
-                                }
-                            }),
-                            EsqlSession::specificValidity
-                        );
+                        indexResolver.resolveAsMergedMapping(indexName, IndexResolver.ALL_FIELDS, refs.acquire(indexResult -> {
+                            if (indexResult.isValid() && indexResult.get().concreteIndices().size() == 1) {
+                                EsIndex esIndex = indexResult.get();
+                                var concreteIndices = Map.of(request.clusterAlias, Iterables.get(esIndex.concreteIndices(), 0));
+                                var resolved = new ResolvedEnrichPolicy(
+                                    p.getMatchField(),
+                                    p.getType(),
+                                    p.getEnrichFields(),
+                                    concreteIndices,
+                                    esIndex.mapping()
+                                );
+                                resolvedPolices.put(policyName, resolved);
+                            } else {
+                                failures.put(policyName, indexResult.toString());
+                            }
+                        }));
                     }
                 }
             }

x-pack/plugin/esql/src/main/java/org/elasticsearch/xpack/esql/execution/PlanExecutor.java

@@ -12,16 +12,15 @@
 import org.elasticsearch.xpack.esql.analysis.PreAnalyzer;
 import org.elasticsearch.xpack.esql.analysis.Verifier;
 import org.elasticsearch.xpack.esql.core.expression.function.FunctionRegistry;
-import org.elasticsearch.xpack.esql.core.index.IndexResolver;
 import org.elasticsearch.xpack.esql.enrich.EnrichPolicyResolver;
 import org.elasticsearch.xpack.esql.expression.function.EsqlFunctionRegistry;
 import org.elasticsearch.xpack.esql.optimizer.LogicalOptimizerContext;
 import org.elasticsearch.xpack.esql.optimizer.LogicalPlanOptimizer;
 import org.elasticsearch.xpack.esql.plan.physical.PhysicalPlan;
 import org.elasticsearch.xpack.esql.planner.Mapper;
 import org.elasticsearch.xpack.esql.session.EsqlConfiguration;
-import org.elasticsearch.xpack.esql.session.EsqlIndexResolver;
 import org.elasticsearch.xpack.esql.session.EsqlSession;
+import org.elasticsearch.xpack.esql.session.IndexResolver;
 import org.elasticsearch.xpack.esql.stats.Metrics;
 import org.elasticsearch.xpack.esql.stats.QueryMetric;
 
@@ -30,16 +29,14 @@
 public class PlanExecutor {
 
     private final IndexResolver indexResolver;
-    private final EsqlIndexResolver esqlIndexResolver;
     private final PreAnalyzer preAnalyzer;
     private final FunctionRegistry functionRegistry;
     private final Mapper mapper;
     private final Metrics metrics;
     private final Verifier verifier;
 
-    public PlanExecutor(IndexResolver indexResolver, EsqlIndexResolver esqlIndexResolver) {
+    public PlanExecutor(IndexResolver indexResolver) {
         this.indexResolver = indexResolver;
-        this.esqlIndexResolver = esqlIndexResolver;
         this.preAnalyzer = new PreAnalyzer();
         this.functionRegistry = new EsqlFunctionRegistry();
         this.mapper = new Mapper(functionRegistry);
@@ -58,7 +55,6 @@ public void esql(
             sessionId,
             cfg,
             indexResolver,
-            esqlIndexResolver,
             enrichPolicyResolver,
             preAnalyzer,
             functionRegistry,

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

@@ -57,21 +57,19 @@
 import org.elasticsearch.xpack.esql.action.RestEsqlQueryAction;
 import org.elasticsearch.xpack.esql.core.expression.Attribute;
 import org.elasticsearch.xpack.esql.core.expression.NamedExpression;
-import org.elasticsearch.xpack.esql.core.index.IndexResolver;
 import org.elasticsearch.xpack.esql.core.type.EsField;
 import org.elasticsearch.xpack.esql.enrich.EnrichLookupOperator;
 import org.elasticsearch.xpack.esql.execution.PlanExecutor;
 import org.elasticsearch.xpack.esql.expression.function.UnsupportedAttribute;
 import org.elasticsearch.xpack.esql.querydsl.query.SingleValueQuery;
-import org.elasticsearch.xpack.esql.session.EsqlIndexResolver;
+import org.elasticsearch.xpack.esql.session.IndexResolver;
 import org.elasticsearch.xpack.esql.type.EsqlDataTypeRegistry;
 
 import java.lang.invoke.MethodHandles;
 import java.util.ArrayList;
 import java.util.Collection;
 import java.util.List;
 import java.util.Objects;
-import java.util.Set;
 import java.util.function.Predicate;
 import java.util.function.Supplier;
 
@@ -110,15 +108,7 @@ public Collection<?> createComponents(PluginServices services) {
         BlockFactory blockFactory = new BlockFactory(circuitBreaker, bigArrays, maxPrimitiveArrayBlockSize);
         setupSharedSecrets();
         return List.of(
-            new PlanExecutor(
-                new IndexResolver(
-                    services.client(),
-                    services.clusterService().getClusterName().value(),
-                    EsqlDataTypeRegistry.INSTANCE,
-                    Set::of
-                ),
-                new EsqlIndexResolver(services.client(), EsqlDataTypeRegistry.INSTANCE)
-            ),
+            new PlanExecutor(new IndexResolver(services.client(), EsqlDataTypeRegistry.INSTANCE)),
             new ExchangeService(services.clusterService().getSettings(), services.threadPool(), ThreadPool.Names.SEARCH, blockFactory),
             blockFactory
         );