[BACKPORT 2.18][#13956] YCQL: Add error message for GROUP BY clause

Summary:
Original commit: 80def06 / D33977
GROUP BY clause is not supported by YCQL, but is allowed in the parser currently, and does not have any effect on the SELECT query. This revision adds an
error message when using GROUP BY clause and also an autoflag ycql_suppress_group_by_error to suppress the error in case of any compatibility issues. Promoting the autoflag makes YCQLsh start throwing the error.
Jira: DB-3446

Test Plan:
```
./yb_build.sh --java-test org.yb.cql.TestCreateTable#testCreateTableWithColumnNamedGroup
./yb_build.sh --java-test org.yb.cql.TestSelect#testGroupBy
```

Reviewers: skumar, stiwary, loginov

Reviewed By: skumar

Subscribers: yql

Tags: #jenkins-ready

Differential Revision: https://phorge.dev.yugabyte.com/D34157

java/yb-cql/src/test/java/org/yb/cql/TestCreateTable.java

@@ -22,6 +22,8 @@
 import static org.yb.AssertionWrappers.assertTrue;
 
 import java.util.Set;
+import java.util.Map;
+import java.util.HashMap;
 
 import org.yb.YBTestRunner;
 import org.junit.runner.RunWith;
@@ -187,6 +189,10 @@ public void testCreateTableWithColumnNamedOffset() throws Exception {
 
   @Test
   public void testCreateTableWithColumnNamedGroup() throws Exception {
+    // Run test with error suppressed as GROUP BY is not supported.
+    Map<String, String> flags = new HashMap<>();
+    flags.put("ycql_suppress_group_by_error", "true");
+    restartClusterWithTSFlags(flags);
     LOG.info("Start test: " + getCurrentTestMethodName());
     testCreateTableWithColumnNamedKeyword("group");
 

java/yb-cql/src/test/java/org/yb/cql/TestSelect.java

@@ -2805,4 +2805,20 @@ public void testMultiColumnInSeeks2() throws Exception {
         assertEquals(2, metrics.seekCount);
     }
   }
+
+  @Test
+  public void testGroupBy() throws Exception
+  {
+    // Expect error in SELECT with GROUP BY.
+    session.execute("CREATE TABLE test_tbl (id int primary key, v int);");
+    runInvalidStmt("SELECT * FROM test_tbl GROUP BY v;");
+
+    // Restart with GROUP BY queries with error suppressed.
+    Map<String, String> flags = new HashMap<>();
+    flags.put("ycql_suppress_group_by_error", "true");
+    restartClusterWithTSFlags(flags);
+
+    session.execute("CREATE TABLE test_tbl (id int primary key, v int);");
+    session.execute("SELECT * FROM test_tbl GROUP BY v;");
+  }
 }

src/yb/yql/cql/ql/parser/parser_gram.y

@@ -102,6 +102,7 @@
 #include "yb/yql/cql/ql/ptree/pt_transaction.h"
 
 DECLARE_bool(cql_raise_index_where_clause_error);
+DECLARE_bool(ycql_suppress_group_by_error);
 
 namespace yb {
 namespace ql {
@@ -203,6 +204,7 @@ using namespace yb::ql;
 
 #define PARSER_INVALID(loc) parser_->Error(loc, ErrorCode::SQL_STATEMENT_INVALID)
 #define PARSER_UNSUPPORTED(loc) parser_->Error(loc, ErrorCode::FEATURE_NOT_SUPPORTED)
+#define PARSER_UNSUPPORTED_MSG(loc, msg) parser_->Error(loc, msg, ErrorCode::FEATURE_NOT_SUPPORTED)
 #define PARSER_NOCODE(loc) parser_->Error(loc, ErrorCode::FEATURE_NOT_YET_IMPLEMENTED)
 
 #define PARSER_CQL_INVALID(loc) parser_->Error(loc, ErrorCode::CQL_STATEMENT_INVALID)
@@ -2517,6 +2519,11 @@ group_clause:
     $$ = nullptr;
   }
   | GROUP_LA BY group_by_list {
+    if(!FLAGS_ycql_suppress_group_by_error)
+      PARSER_UNSUPPORTED_MSG(@1,
+        "This is not recommended but this error can be suppressed by setting " \
+        "ycql_suppress_group_by_error flag to false. When set to false, " \
+        "the error will be suppressed but the GROUP BY clause will be ignored.");
     $$ = $3;
   }
 ;

src/yb/yql/cql/ql/ptree/pt_select.cc

@@ -54,6 +54,9 @@ DEFINE_UNKNOWN_bool(enable_uncovered_index_select, true,
             "Enable executing select statements using uncovered index");
 TAG_FLAG(enable_uncovered_index_select, advanced);
 
+DEFINE_RUNTIME_AUTO_bool(ycql_suppress_group_by_error, kLocalVolatile, true, false,
+            "Enable to suppress the error raised when using GROUP BY clause");
+
 namespace yb {
 namespace ql {