[#9279] YSQL: Enable -Wextra on yql folder

Summary:
As a part of enabling -Wextra on entire code base this diff enables flags on yql directory.

All new warnings are fixed in context of this diff. Compilation was tested on GCC9.

Test Plan: Jenkins

Reviewers: sergei, timur, alex

Reviewed By: alex

Subscribers: yql

Differential Revision: https://phabricator.dev.yugabyte.com/D12786

CMakeLists.txt

@@ -687,12 +687,7 @@ set(YB_TEST_LINK_LIBS ${YB_MIN_TEST_LIBS})
 
 # TODO(dmitry): Add YB_CMAKE_CXX_EXTRA_FLAGS to CMAKE_CXX_FLAGS when all source code will be
 #               compatible with with these flags #9279
-# Note: YB_CMAKE_CXX_EXTRA_FLAGS almost equals to flags in ./src/yb/rocksdb/CMakeLists.txt
-#       Exceptions are:
-#         * No -Wsign-compare because for now YB uses -Wno-sign-compare explicitly
-#         * No -Wno-unused-variable and -Wno-missing-field-initializers because there are no
-#           such warnings in the YB code
-set(YB_CMAKE_CXX_EXTRA_FLAGS "-Wextra -Wshadow -Woverloaded-virtual -Wno-unused-parameter")
+set(YB_CMAKE_CXX_EXTRA_FLAGS "-Wextra -Wno-unused-parameter")
 
 # For any C code, use the same flags as for C++.
 set(CMAKE_C_FLAGS "${CMAKE_CXX_FLAGS}")

src/yb/util/decimal.h

@@ -89,6 +89,13 @@ class Decimal {
           bool is_positive = true)
       : digits_(digits), exponent_(exponent), is_positive_(is_positive) { make_canonical(); }
   Decimal(const Decimal& other) : Decimal(other.digits_, other.exponent_, other.is_positive_) {}
+  Decimal& operator=(const Decimal& other) {
+    digits_ = other.digits_;
+    exponent_ = other.exponent_;
+    is_positive_ = other.is_positive_;
+    make_canonical();
+    return *this;
+  }
 
   // Ensure the type conversion is possible if you use these constructors. Use FromX() otherwise.
   explicit Decimal(const std::string& string_val) { CHECK_OK(FromString(string_val)); }

src/yb/yql/CMakeLists.txt

@@ -11,6 +11,9 @@
 # under the License.
 #
 
+# TODO(dmitry): Remove next line after fixing #9279
+set(CMAKE_CXX_FLAGS "${YB_CMAKE_CXX_EXTRA_FLAGS} ${CMAKE_CXX_FLAGS}")
+
 # CQL service
 add_subdirectory(cql/ql)
 add_subdirectory(cql/cqlserver)

src/yb/yql/cql/ql/audit/audit_logger.cc

@@ -646,7 +646,7 @@ Result<LogEntry> AuditLogger::CreateLogEntry(const Type& type,
     .operation     = std::move(operation),
     .error_message = std::move(error_message)
   };
-  return std::move(entry);
+  return entry;
 }
 
 Status AuditLogger::StartBatchRequest(int statements_count,

src/yb/yql/cql/ql/ptree/pt_grant_revoke.h

@@ -136,7 +136,7 @@ class PTGrantRevokePermission : public TreeNode {
     return role_name_;
   }
 
-  const ResourceType resource_type() const {
+  ResourceType resource_type() const {
     return resource_type_;
   }
 
@@ -157,7 +157,7 @@ class PTGrantRevokePermission : public TreeNode {
     return nullptr;
   }
 
-  const PermissionType permission() const {
+  PermissionType permission() const {
     return permission_;
   }
 

src/yb/yql/cql/ql/util/statement_params.h

@@ -77,7 +77,7 @@ class StatementParameters {
     return STATUS(RuntimeError, "no bind variable available");
   }
 
-  const YBConsistencyLevel yb_consistency_level() const {
+  YBConsistencyLevel yb_consistency_level() const {
     return yb_consistency_level_;
   }
 

src/yb/yql/cql/ql/util/statement_result.h

@@ -82,7 +82,7 @@ class ExecutedResult {
     SCHEMA_CHANGE = 3
   };
 
-  virtual const Type type() const = 0;
+  virtual Type type() const = 0;
 };
 
 // Callback to be called after a statement is executed. When execution fails, a not-ok status is
@@ -103,7 +103,7 @@ class SetKeyspaceResult : public ExecutedResult {
   virtual ~SetKeyspaceResult() override { };
 
   // Result type.
-  virtual const Type type() const override { return Type::SET_KEYSPACE; }
+  Type type() const override { return Type::SET_KEYSPACE; }
 
   // Accessor function for keyspace.
   const std::string& keyspace() const { return keyspace_; }
@@ -129,7 +129,7 @@ class RowsResult : public ExecutedResult {
   virtual ~RowsResult() override;
 
   // Result type.
-  virtual const Type type() const override { return Type::ROWS; }
+  Type type() const override { return Type::ROWS; }
 
   // Accessor functions.
   const client::YBTableName& table_name() const { return table_name_; }
@@ -178,7 +178,7 @@ class SchemaChangeResult : public ExecutedResult {
   virtual ~SchemaChangeResult() override;
 
   // Result type.
-  virtual const Type type() const override { return Type::SCHEMA_CHANGE; }
+  Type type() const override { return Type::SCHEMA_CHANGE; }
 
   // Accessor functions.
   const std::string& change_type() const { return change_type_; }

src/yb/yql/pggate/CMakeLists.txt

@@ -14,9 +14,6 @@
 # We need access to the generated pg_type_d.h header from this directory.
 include_directories("${YB_BUILD_ROOT}/postgres_build/src/include")
 
-# TODO(dmitry): Remove next line after fixing #9279
-set(CMAKE_CXX_FLAGS "${YB_CMAKE_CXX_EXTRA_FLAGS} ${CMAKE_CXX_FLAGS}")
-
 # Utility functions that are specific for PGGate.
 add_subdirectory(util)
 

src/yb/yql/pgwrapper/CMakeLists.txt

@@ -11,9 +11,6 @@
 # under the License.
 #
 
-# TODO(dmitry): Remove next line after fixing #9279
-set(CMAKE_CXX_FLAGS "${YB_CMAKE_CXX_EXTRA_FLAGS} ${CMAKE_CXX_FLAGS}")
-
 set(PGWRAPPER_SRCS
     pg_wrapper.cc)
 set(PGWRAPPER_LIBS