Bug#28865321: MAKE THD METHODS CONST WHEN POSSIBLE

Mark a number of THD methods as const so that it is obvious
that they do not modify THD state and to allow more usage of
const THD pointers.

Change-Id: If6d8881ae86e2131a2e3fa0d449f55532dc2f958

Author: jhauglid

Diff for: include/violite.h

@@ -169,7 +169,7 @@ bool vio_was_timeout(MYSQL_VIO vio);
 #define VIO_DESCRIPTION_SIZE 30 /* size of description */
 void vio_description(MYSQL_VIO vio, char *buf);
 /* Return the type of the connection */
-enum enum_vio_type vio_type(MYSQL_VIO vio);
+enum enum_vio_type vio_type(const MYSQL_VIO vio);
 /* Return last error number */
 int vio_errno(MYSQL_VIO vio);
 /* Get socket number */

Diff for: sql/binlog.cc

@@ -177,6 +177,8 @@ static xa_status_code binlog_xa_rollback(handlerton *hton, XID *xid);
 static void exec_binlog_error_action_abort(const char *err_string);
 static int binlog_recover(Binlog_file_reader *binlog_file_reader,
                           my_off_t *valid_pos);
+static bool binlog_row_event_extra_data_eq(const uchar *a, const uchar *b);
+static void binlog_prepare_row_images(const THD *thd, TABLE *table);
 
 static inline bool has_commit_order_manager(THD *thd) {
   return is_mts_worker(thd) &&
@@ -3043,7 +3045,7 @@ bool purge_master_logs_before_date(THD *thd, time_t purge_time) {
 /*
   Helper function to get the error code of the query to be binlogged.
  */
-int query_error_code(THD *thd, bool not_killed) {
+int query_error_code(const THD *thd, bool not_killed) {
   int error;
 
   if (not_killed) {
@@ -5137,7 +5139,7 @@ int MYSQL_BIN_LOG::raw_get_current_log(LOG_INFO *linfo) {
   return 0;
 }
 
-bool MYSQL_BIN_LOG::check_write_error(THD *thd) {
+bool MYSQL_BIN_LOG::check_write_error(const THD *thd) {
   DBUG_ENTER("MYSQL_BIN_LOG::check_write_error");
 
   bool checked = false;
@@ -8933,7 +8935,7 @@ inline void MYSQL_BIN_LOG::update_binlog_end_pos(const char *file,
   unlock_binlog_end_pos();
 }
 
-bool THD::is_binlog_cache_empty(bool is_transactional) {
+bool THD::is_binlog_cache_empty(bool is_transactional) const {
   DBUG_ENTER("THD::is_binlog_cache_empty(bool)");
 
   // If opt_bin_log==0, it is not safe to call thd_get_cache_mngr
@@ -10651,7 +10653,7 @@ int THD::binlog_update_row(TABLE *table, bool is_trans,
      not needed for binlogging. This is done according to the:
      binlog-row-image option.
    */
-  binlog_prepare_row_images(table);
+  binlog_prepare_row_images(this, table);
 
   Row_data_memory row_data(table, before_record, after_record,
                            variables.binlog_row_value_options);
@@ -10706,7 +10708,7 @@ int THD::binlog_delete_row(TABLE *table, bool is_trans, uchar const *record,
      not needed for binlogging. This is done according to the:
      binlog-row-image option.
    */
-  binlog_prepare_row_images(table);
+  binlog_prepare_row_images(this, table);
 
   /*
      Pack records into format for transfer. We are allocating more
@@ -10737,7 +10739,7 @@ int THD::binlog_delete_row(TABLE *table, bool is_trans, uchar const *record,
   return error;
 }
 
-void THD::binlog_prepare_row_images(TABLE *table) {
+void binlog_prepare_row_images(const THD *thd, TABLE *table) {
   DBUG_ENTER("THD::binlog_prepare_row_images");
   /**
     Remove from read_set spurious columns. The write_set has been
@@ -10746,7 +10748,6 @@ void THD::binlog_prepare_row_images(TABLE *table) {
 
   DBUG_PRINT_BITSET("debug", "table->read_set (before preparing): %s",
                     table->read_set);
-  THD *thd = table->in_use;
 
   /**
     if there is a primary key in the table (ie, user declared PK or a
@@ -10844,7 +10845,7 @@ int THD::binlog_flush_pending_rows_event(bool stmt_end, bool is_transactional) {
    @return
      true if the referenced structures are equal
 */
-bool THD::binlog_row_event_extra_data_eq(const uchar *a, const uchar *b) {
+static bool binlog_row_event_extra_data_eq(const uchar *a, const uchar *b) {
   return ((a == b) ||
           ((a != NULL) && (b != NULL) &&
            (a[EXTRA_ROW_INFO_LEN_OFFSET] == b[EXTRA_ROW_INFO_LEN_OFFSET]) &&

Diff for: sql/binlog.h

@@ -755,7 +755,7 @@ class MYSQL_BIN_LOG : public TC_LOG {
   bool write_dml_directly(THD *thd, const char *stmt, size_t stmt_len);
 
   void report_cache_write_error(THD *thd, bool is_transactional);
-  bool check_write_error(THD *thd);
+  bool check_write_error(const THD *thd);
   bool write_incident(THD *thd, bool need_lock_log, const char *err_msg,
                       bool do_flush_and_sync = true);
   bool write_incident(Incident_log_event *ev, THD *thd, bool need_lock_log,
@@ -930,7 +930,7 @@ void check_binlog_cache_size(THD *thd);
 void check_binlog_stmt_cache_size(THD *thd);
 bool binlog_enabled();
 void register_binlog_handler(THD *thd, bool trx);
-int query_error_code(THD *thd, bool not_killed);
+int query_error_code(const THD *thd, bool not_killed);
 
 extern const char *log_bin_index;
 extern const char *log_bin_basename;

Diff for: sql/mdl.h

@@ -164,7 +164,7 @@ class MDL_context_owner {
     Get random seed specific to this THD to be used for initialization
     of PRNG for the MDL_context.
   */
-  virtual uint get_rand_seed() = 0;
+  virtual uint get_rand_seed() const = 0;
 };
 
 /**

Diff for: sql/mdl_context_backup.cc

@@ -78,7 +78,7 @@ class MDL_context_backup_manager::MDL_context_backup
 
   void notify_hton_post_release_exclusive(const MDL_key *) override { return; }
 
-  uint get_rand_seed() override { return (uint)1; }
+  uint get_rand_seed() const override { return 1; }
 
   bool is_connected() override { return true; }
   // End implementation of MDL_context_owner interface.

Diff for: sql/protocol.h

@@ -122,9 +122,9 @@ class Protocol {
   */
   enum { SEND_NUM_ROWS = 1, SEND_DEFAULTS = 2, SEND_EOF = 4 };
 
-  virtual enum enum_protocol_type type() = 0;
+  virtual enum enum_protocol_type type() const = 0;
 
-  virtual enum enum_vio_type connection_type() = 0;
+  virtual enum enum_vio_type connection_type() const = 0;
 
   /* Data sending functions */
   virtual bool store_null() = 0;
@@ -194,7 +194,7 @@ class Protocol {
       true    if the connection is still alive
       false   otherwise
    */
-  virtual bool connection_alive() = 0;
+  virtual bool connection_alive() const = 0;
 
   /**
     Result set sending functions

Diff for: sql/protocol_callback.cc

@@ -78,7 +78,7 @@ int Protocol_callback::get_command(COM_DATA *, enum_server_command *) {
   @return
     VIO_TYPE_PLUGIN
 */
-enum enum_vio_type Protocol_callback::connection_type() {
+enum enum_vio_type Protocol_callback::connection_type() const {
   return VIO_TYPE_PLUGIN;
 }
 
@@ -266,7 +266,7 @@ int Protocol_callback::shutdown(bool server_shutdown) {
   @return
     true  alive
 */
-bool Protocol_callback::connection_alive() { return true; }
+bool Protocol_callback::connection_alive() const { return true; }
 
 /**
   Should return protocol's reading/writing status. Returns 0 (idle) as it this

Diff for: sql/protocol_callback.h

@@ -85,15 +85,15 @@ class Protocol_callback : public Protocol {
       false  success
       true   failure
   */
-  virtual enum enum_protocol_type type() { return PROTOCOL_PLUGIN; }
+  virtual enum enum_protocol_type type() const { return PROTOCOL_PLUGIN; }
 
   /**
     Returns the type of the connection
 
     @return
       enum enum_vio_type
   */
-  virtual enum enum_vio_type connection_type();
+  virtual enum enum_vio_type connection_type() const;
 
   /**
     Sends null value
@@ -300,7 +300,7 @@ class Protocol_callback : public Protocol {
     @return
       true   alive
   */
-  virtual bool connection_alive();
+  virtual bool connection_alive() const;
 
   /**
     Should return protocol's reading/writing status. Returns 0 (idle) as it

Diff for: sql/protocol_classic.cc

@@ -1356,6 +1356,8 @@ NET *Protocol_classic::get_net() { return &m_thd->net; }
 
 Vio *Protocol_classic::get_vio() { return m_thd->net.vio; }
 
+const Vio *Protocol_classic::get_vio() const { return m_thd->net.vio; }
+
 void Protocol_classic::set_vio(Vio *vio) { m_thd->net.vio = vio; }
 
 void Protocol_classic::set_output_pkt_nr(uint pkt_nr) {
@@ -3156,7 +3158,9 @@ bool store(Protocol *prot, I_List<i_string> *str_list) {
   All data are sent as 'packed-string-length' followed by 'string-data'
 ****************************************************************************/
 
-bool Protocol_classic::connection_alive() { return m_thd->net.vio != NULL; }
+bool Protocol_classic::connection_alive() const {
+  return m_thd->net.vio != nullptr;
+}
 
 void Protocol_text::start_row() {
 #ifndef DBUG_OFF

Diff for: sql/protocol_classic.h

@@ -130,16 +130,16 @@ class Protocol_classic : public Protocol {
   virtual bool send_field_metadata(Send_field *field,
                                    const CHARSET_INFO *item_charset);
   virtual void abort_row() {}
-  virtual enum enum_protocol_type type() = 0;
+  virtual enum enum_protocol_type type() const = 0;
 
   /**
     Returns the type of the connection
 
     @return
       enum enum_vio_type
   */
-  virtual enum enum_vio_type connection_type() {
-    Vio *v = get_vio();
+  virtual enum enum_vio_type connection_type() const {
+    const Vio *v = get_vio();
     return v ? vio_type(v) : NO_VIO_TYPE;
   }
 
@@ -161,7 +161,7 @@ class Protocol_classic : public Protocol {
   /* Wipe NET with zeros */
   void wipe_net();
   /* Check whether VIO is healhty */
-  virtual bool connection_alive();
+  virtual bool connection_alive() const;
   /* Returns the client capabilities */
   virtual ulong get_client_capabilities() { return m_client_capabilities; }
   /* Sets the client capabilities */
@@ -186,6 +186,7 @@ class Protocol_classic : public Protocol {
   NET *get_net();
   /* return VIO */
   Vio *get_vio();
+  const Vio *get_vio() const;
   /* Set VIO */
   void set_vio(Vio *vio);
   /* Set packet number */
@@ -228,7 +229,7 @@ class Protocol_text : public Protocol_classic {
   virtual void start_row();
   virtual bool send_parameters(List<Item_param> *parameters, bool);
 
-  virtual enum enum_protocol_type type() { return PROTOCOL_TEXT; }
+  virtual enum enum_protocol_type type() const { return PROTOCOL_TEXT; }
 
  protected:
   virtual bool store(const char *from, size_t length,
@@ -264,7 +265,7 @@ class Protocol_binary : public Protocol_text {
   virtual bool send_parameters(List<Item_param> *parameters,
                                bool is_sql_prepare);
 
-  virtual enum enum_protocol_type type() { return PROTOCOL_BINARY; }
+  virtual enum enum_protocol_type type() const { return PROTOCOL_BINARY; }
 
  protected:
   virtual bool store(const char *from, size_t length,

Diff for: sql/sql_class.cc

@@ -1540,7 +1540,7 @@ int THD::send_explain_fields(Query_result *result) {
       this, field_list, Protocol::SEND_NUM_ROWS | Protocol::SEND_EOF));
 }
 
-enum_vio_type THD::get_vio_type() {
+enum_vio_type THD::get_vio_type() const {
   DBUG_ENTER("THD::get_vio_type");
   DBUG_RETURN(get_protocol()->connection_type());
 }
@@ -2606,7 +2606,7 @@ void THD::rpl_reattach_engine_ha_data() {
   if (rli) rli->reattach_engine_ha_data(this);
 }
 
-bool THD::rpl_unflag_detached_engine_ha_data() {
+bool THD::rpl_unflag_detached_engine_ha_data() const {
   Relay_log_info *rli =
       is_binlog_applier() ? rli_fake : (slave_thread ? rli_slave : NULL);
   return rli ? rli->unflag_detached_engine_ha_data() : false;