Cleanup session tracker redundancy

- m_enabled is initialised by the base class constructor
- removed unused schema_track_inited
- moved Transaction_state_tracker constructor to declaration
- common enable()
- removed unused Session_sysvars_tracker::check_str()
- classes are "private" by default
- don't even try to compile for embedded

Part of MDEV-14984 - regression in connect performance

libmysqld/CMakeLists.txt

@@ -117,7 +117,6 @@ SET(SQL_EMBEDDED_SOURCES emb_qcache.cc libmysqld.c lib_sql.cc
            ../sql/sql_sequence.cc ../sql/sql_sequence.h
            ../sql/ha_sequence.cc ../sql/ha_sequence.h
            ../sql/temporary_tables.cc
-           ../sql/session_tracker.cc
            ../sql/proxy_protocol.cc
            ../sql/sql_tvc.cc ../sql/sql_tvc.h
            ../sql/opt_split.cc

sql/session_tracker.cc

@@ -15,7 +15,6 @@
    Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301  USA */
 
 
-#ifndef EMBEDDED_LIBRARY
 #include "sql_plugin.h"
 #include "session_tracker.h"
 
@@ -60,8 +59,6 @@ class Not_implemented_tracker : public State_tracker
 
 class Session_sysvars_tracker : public State_tracker
 {
-private:
-
   struct sysvar_node_st {
     sys_var *m_svar;
     bool *test_load;
@@ -216,7 +213,6 @@ class Session_sysvars_tracker : public State_tracker
   }
 
   bool enable(THD *thd);
-  bool check_str(THD *thd, LEX_STRING *val);
   bool update(THD *thd, set_var *var);
   bool store(THD *thd, String *buf);
   void mark_as_changed(THD *thd, LEX_CSTRING *tracked_item_name);
@@ -239,18 +235,7 @@ class Session_sysvars_tracker : public State_tracker
 
 class Current_schema_tracker : public State_tracker
 {
-private:
-  bool schema_track_inited;
-
 public:
-
-  Current_schema_tracker()
-  {
-    schema_track_inited= false;
-  }
-
-  bool enable(THD *thd)
-  { return update(thd, NULL); }
   bool update(THD *thd, set_var *var);
   bool store(THD *thd, String *buf);
 };
@@ -272,8 +257,6 @@ class Current_schema_tracker : public State_tracker
 class Session_state_change_tracker : public State_tracker
 {
 public:
-  bool enable(THD *thd)
-  { return update(thd, NULL); };
   bool update(THD *thd, set_var *var);
   bool store(THD *thd, String *buf);
 };
@@ -654,27 +637,6 @@ bool Session_sysvars_tracker::enable(THD *thd)
 }
 
 
-/**
-  Check system variable name(s).
-
-  @note This function is called from the ON_CHECK() function of the
-        session_track_system_variables' sys_var class.
-
-  @param thd    [IN]        The thd handle.
-  @param var    [IN]        A pointer to set_var holding the specified list of
-                            system variable names.
-
-  @retval true  Error
-  @retval false Success
-*/
-
-inline bool Session_sysvars_tracker::check_str(THD *thd, LEX_STRING *val)
-{
-  return Session_sysvars_tracker::check_var_list(thd, *val, true,
-                                                 thd->charset(), true);
-}
-
-
 /**
   Once the value of the @@session_track_system_variables has been
   successfully updated, this function calls
@@ -936,17 +898,6 @@ bool Current_schema_tracker::store(THD *thd, String *buf)
 
 ///////////////////////////////////////////////////////////////////////////////
 
-
-Transaction_state_tracker::Transaction_state_tracker()
-{
-  m_enabled        = false;
-  tx_changed       = TX_CHG_NONE;
-  tx_curr_state    =
-  tx_reported_state= TX_EMPTY;
-  tx_read_flags    = TX_READ_INHERIT;
-  tx_isol_level    = TX_ISOL_INHERIT;
-}
-
 /**
   Enable/disable the tracker based on @@session_track_transaction_info.
 
@@ -1597,5 +1548,3 @@ void Session_tracker::store(THD *thd, String *buf)
 
   net_store_length(data - 1, length);
 }
-
-#endif //EMBEDDED_LIBRARY

sql/session_tracker.h

@@ -90,7 +90,7 @@ class State_tracker
   void reset_changed() { m_changed= false; }
 
   /** Called in the constructor of THD*/
-  virtual bool enable(THD *thd)= 0;
+  virtual bool enable(THD *thd) { return update(thd, 0); }
 
   /** To be invoked when the tracker's system variable is updated (ON_UPDATE).*/
   virtual bool update(THD *thd, set_var *var)= 0;
@@ -119,7 +119,6 @@ bool sysvartrack_value_construct(THD *thd, char *val, size_t len);
 
 class Session_tracker
 {
-private:
   State_tracker *m_trackers[SESSION_TRACKER_END];
 
   /* The following two functions are private to disable copying. */
@@ -234,14 +233,16 @@ enum enum_session_track_transaction_info {
 
 class Transaction_state_tracker : public State_tracker
 {
-private:
   /** Helper function: turn table info into table access flag */
   enum_tx_state calc_trx_state(THD *thd, thr_lock_type l, bool has_trx);
 public:
   /** Constructor */
-  Transaction_state_tracker();
-  bool enable(THD *thd)
-  { return update(thd, NULL); }
+  Transaction_state_tracker(): tx_changed(TX_CHG_NONE),
+                               tx_curr_state(TX_EMPTY),
+                               tx_reported_state(TX_EMPTY),
+                               tx_read_flags(TX_READ_INHERIT),
+                               tx_isol_level(TX_ISOL_INHERIT) {}
+
   bool update(THD *thd, set_var *var);
   bool store(THD *thd, String *buf);