Fix analytics engine routing for SQL after V2 parser change

The switch from CalciteSqlQueryParser to SqlV2QueryParser (#5438) changed
the parse return type from SqlNode to UnresolvedPlan. This caused a
ClassCastException in extractIndexName(), which was silently caught and
returned false, routing all SQL queries to V2 engine instead of analytics.

Fix: unify SQL and PPL paths to both use UnresolvedPlan + IndexNameExtractor.
Remove dead SqlNode-based extraction code (SqlTableNameExtractor).

Signed-off-by: Chen Dai <daichen@amazon.com>

Author: dai-chen

plugin/src/main/java/org/opensearch/sql/plugin/rest/RestUnifiedQueryAction.java

@@ -13,12 +13,6 @@
 import java.util.Map;
 import java.util.Optional;
 import org.apache.calcite.rel.RelNode;
-import org.apache.calcite.sql.SqlCall;
-import org.apache.calcite.sql.SqlIdentifier;
-import org.apache.calcite.sql.SqlJoin;
-import org.apache.calcite.sql.SqlNode;
-import org.apache.calcite.sql.SqlSelect;
-import org.apache.calcite.sql.util.SqlBasicVisitor;
 import org.apache.logging.log4j.LogManager;
 import org.apache.logging.log4j.Logger;
 import org.apache.logging.log4j.ThreadContext;
@@ -213,12 +207,8 @@ private UnifiedQueryContext.Builder applyClusterOverrides(UnifiedQueryContext.Bu
    */
   private static Optional<String> extractIndexName(
       String query, QueryType queryType, UnifiedQueryContext context) {
-    if (queryType == QueryType.PPL) {
-      UnresolvedPlan unresolvedPlan = (UnresolvedPlan) context.getParser().parse(query);
-      return Optional.ofNullable(unresolvedPlan.accept(new IndexNameExtractor(), null));
-    }
-    SqlNode sqlNode = (SqlNode) context.getParser().parse(query);
-    return Optional.ofNullable(extractTableNameFromSqlNode(sqlNode));
+    UnresolvedPlan unresolvedPlan = (UnresolvedPlan) context.getParser().parse(query);
+    return Optional.ofNullable(unresolvedPlan.accept(new IndexNameExtractor(), null));
   }
 
   /** AST visitor that extracts the source index name from a Relation node (PPL path). */
@@ -229,29 +219,6 @@ public String visitRelation(Relation node, Void context) {
     }
   }
 
-  /** SqlNode visitor that extracts the source table name from a SQL parse tree. */
-  private static class SqlTableNameExtractor extends SqlBasicVisitor<String> {
-    @Override
-    public String visit(SqlCall call) {
-      if (call instanceof SqlSelect select) {
-        return select.getFrom().accept(this);
-      }
-      if (call instanceof SqlJoin join) {
-        return join.getLeft().accept(this);
-      }
-      return null;
-    }
-
-    @Override
-    public String visit(SqlIdentifier id) {
-      return id.toString();
-    }
-  }
-
-  private static String extractTableNameFromSqlNode(SqlNode sqlNode) {
-    return sqlNode.accept(new SqlTableNameExtractor());
-  }
-
   private static RelNode addQuerySizeLimit(RelNode plan, CalcitePlanContext context) {
     return LogicalSystemLimit.create(
         LogicalSystemLimit.SystemLimitType.QUERY_SIZE_LIMIT,

plugin/src/test/java/org/opensearch/sql/plugin/rest/RestUnifiedQueryActionTest.java

@@ -89,10 +89,51 @@ public void missingIndexRoutesToLucene() {
     assertFalse(action.isAnalyticsIndex("source = does_not_exist | fields ts", QueryType.PPL));
   }
 
+  @Test
+  public void sqlQueryRoutesToAnalyticsForPluggableIndex() {
+    registerIndex(
+        "parquet_logs",
+        Settings.builder()
+            .put(IndexSettings.PLUGGABLE_DATAFORMAT_ENABLED_SETTING.getKey(), true)
+            .put(IndexSettings.PLUGGABLE_DATAFORMAT_VALUE_SETTING.getKey(), "composite")
+            .build());
+
+    assertTrue(action.isAnalyticsIndex("SELECT * FROM parquet_logs", QueryType.SQL));
+    assertTrue(
+        action.isAnalyticsIndex(
+            "SELECT ts, level FROM parquet_logs WHERE level = 'ERROR'", QueryType.SQL));
+  }
+
+  @Test
+  public void sqlQueryWithSchemaRoutesToAnalytics() {
+    registerIndex(
+        "parquet_logs",
+        Settings.builder()
+            .put(IndexSettings.PLUGGABLE_DATAFORMAT_ENABLED_SETTING.getKey(), true)
+            .put(IndexSettings.PLUGGABLE_DATAFORMAT_VALUE_SETTING.getKey(), "composite")
+            .build());
+
+    assertTrue(action.isAnalyticsIndex("SELECT * FROM opensearch.parquet_logs", QueryType.SQL));
+  }
+
+  @Test
+  public void sqlQueryRoutesToLuceneForNonPluggableIndex() {
+    registerIndex("plain_logs", Settings.EMPTY);
+
+    assertFalse(action.isAnalyticsIndex("SELECT * FROM plain_logs", QueryType.SQL));
+  }
+
+  @Test
+  public void sqlQueryRoutesToLuceneForMissingIndex() {
+    assertFalse(action.isAnalyticsIndex("SELECT * FROM does_not_exist", QueryType.SQL));
+  }
+
   @Test
   public void nullAndEmptyQueriesRouteToLucene() {
     assertFalse(action.isAnalyticsIndex(null, QueryType.PPL));
     assertFalse(action.isAnalyticsIndex("", QueryType.PPL));
+    assertFalse(action.isAnalyticsIndex(null, QueryType.SQL));
+    assertFalse(action.isAnalyticsIndex("", QueryType.SQL));
   }
 
   private void registerIndex(String name, Settings settings) {