Dead code removal: sess_t

The session object is not really needed for anything.
We can directly create and free the dummy purge_sys->query->trx.

storage/innobase/CMakeLists.txt

@@ -137,7 +137,6 @@ SET(INNOBASE_SOURCES
 	trx/trx0sys.cc
 	trx/trx0trx.cc
 	trx/trx0undo.cc
-	usr/usr0sess.cc
 	ut/ut0crc32.cc
 	ut/ut0dbg.cc
 	ut/ut0list.cc

storage/innobase/dict/dict0crea.cc

 /*****************************************************************************
 
 Copyright (c) 1996, 2016, Oracle and/or its affiliates. All Rights Reserved.
-Copyright (c) 2017, MariaDB Corporation.
+Copyright (c) 2017, 2018, MariaDB Corporation.
 
 This program is free software; you can redistribute it and/or modify it under
 the terms of the GNU General Public License as published by the Free Software
@@ -38,7 +38,6 @@ Created 1/8/1996 Heikki Tuuri
 #include "row0mysql.h"
 #include "pars0pars.h"
 #include "trx0roll.h"
-#include "usr0sess.h"
 #include "ut0vec.h"
 #include "dict0priv.h"
 #include "fts0priv.h"

storage/innobase/include/pars0opt.h

 /*****************************************************************************
 
 Copyright (c) 1997, 2016, Oracle and/or its affiliates. All Rights Reserved.
-Copyright (c) 2017, MariaDB Corporation.
+Copyright (c) 2017, 2018, MariaDB Corporation.
 
 This program is free software; you can redistribute it and/or modify it under
 the terms of the GNU General Public License as published by the Free Software
@@ -29,7 +29,6 @@ Created 12/21/1997 Heikki Tuuri
 
 #include "univ.i"
 #include "que0types.h"
-#include "usr0types.h"
 #include "pars0sym.h"
 #include "dict0types.h"
 #include "row0sel.h"

storage/innobase/include/pars0pars.h

 /*****************************************************************************
 
 Copyright (c) 1996, 2016, Oracle and/or its affiliates. All Rights Reserved.
-Copyright (c) 2017, MariaDB Corporation.
+Copyright (c) 2017, 2018, MariaDB Corporation.
 
 This program is free software; you can redistribute it and/or modify it under
 the terms of the GNU General Public License as published by the Free Software
@@ -29,7 +29,6 @@ Created 11/19/1996 Heikki Tuuri
 
 #include "univ.i"
 #include "que0types.h"
-#include "usr0types.h"
 #include "pars0types.h"
 #include "row0types.h"
 #include "trx0types.h"

storage/innobase/include/pars0sym.h

 /*****************************************************************************
 
 Copyright (c) 1997, 2016, Oracle and/or its affiliates. All Rights Reserved.
-Copyright (c) 2017, MariaDB Corporation.
+Copyright (c) 2017, 2018, MariaDB Corporation.
 
 This program is free software; you can redistribute it and/or modify it under
 the terms of the GNU General Public License as published by the Free Software
@@ -29,7 +29,6 @@ Created 12/15/1997 Heikki Tuuri
 
 #include "univ.i"
 #include "que0types.h"
-#include "usr0types.h"
 #include "dict0types.h"
 #include "pars0types.h"
 #include "row0types.h"

storage/innobase/include/que0que.h

 /*****************************************************************************
 
 Copyright (c) 1996, 2016, Oracle and/or its affiliates. All Rights Reserved.
-Copyright (c) 2017, MariaDB Corporation.
+Copyright (c) 2017, 2018, MariaDB Corporation.
 
 This program is free software; you can redistribute it and/or modify it under
 the terms of the GNU General Public License as published by the Free Software
@@ -33,7 +33,6 @@ Created 5/27/1996 Heikki Tuuri
 #include "trx0trx.h"
 #include "trx0roll.h"
 #include "srv0srv.h"
-#include "usr0types.h"
 #include "que0types.h"
 #include "row0types.h"
 #include "pars0types.h"

storage/innobase/include/que0que.ic

@@ -23,8 +23,6 @@ Query graph
 Created 5/27/1996 Heikki Tuuri
 *******************************************************/
 
-#include "usr0sess.h"
-
 /***********************************************************************//**
 Gets the trx of a query thread. */
 UNIV_INLINE

storage/innobase/include/trx0purge.h

 /*****************************************************************************
 
 Copyright (c) 1996, 2016, Oracle and/or its affiliates. All Rights Reserved.
-Copyright (c) 2017, MariaDB Corporation. All Rights Reserved.
+Copyright (c) 2017, 2018, MariaDB Corporation.
 
 This program is free software; you can redistribute it and/or modify it under
 the terms of the GNU General Public License as published by the Free Software
@@ -33,7 +33,6 @@ Created 3/26/1996 Heikki Tuuri
 #include "trx0sys.h"
 #include "que0types.h"
 #include "page0page.h"
-#include "usr0sess.h"
 #include "fil0fil.h"
 #include "read0types.h"
 
@@ -494,8 +493,6 @@ class purge_sys_t
 	/** Destruct the purge system. */
 	~purge_sys_t();
 
-	sess_t*		sess;		/*!< System session running the purge
-					query */
 	rw_lock_t	latch;		/*!< The latch protecting the purge
 					view. A purge operation must acquire an
 					x-latch here for the instant at which

storage/innobase/include/trx0trx.h

 /*****************************************************************************
 
 Copyright (c) 1996, 2016, Oracle and/or its affiliates. All Rights Reserved.
-Copyright (c) 2015, 2017, MariaDB Corporation.
+Copyright (c) 2015, 2018, MariaDB Corporation.
 
 This program is free software; you can redistribute it and/or modify it under
 the terms of the GNU General Public License as published by the Free Software
@@ -38,7 +38,6 @@ Created 3/26/1996 Heikki Tuuri
 
 #include "lock0types.h"
 #include "log0log.h"
-#include "usr0types.h"
 #include "que0types.h"
 #include "mem0mem.h"
 #include "trx0xa.h"
@@ -55,9 +54,6 @@ class ReadView;
 // Forward declaration
 class FlushObserver;
 
-/** Dummy session used currently in MySQL interface */
-extern sess_t*	trx_dummy_sess;
-
 /** Set flush observer for the transaction
 @param[in/out]	trx		transaction struct
 @param[in]	observer	flush observer */
@@ -1139,7 +1135,6 @@ struct trx_t {
 	ulint		error_key_num;	/*!< if the index creation fails to a
 					duplicate key error, a mysql key
 					number of that index is stored here */
-	sess_t*		sess;		/*!< session of the trx, NULL if none */
 	que_t*		graph;		/*!< query currently run in the session,
 					or NULL if none; NOTE that the query
 					belongs to the session, and it can

storage/innobase/include/usr0sess.h

-/*****************************************************************************
-
-Copyright (c) 1996, 2016, Oracle and/or its affiliates. All Rights Reserved.
-Copyright (c) 2017, MariaDB Corporation.
-
-This program is free software; you can redistribute it and/or modify it under
-the terms of the GNU General Public License as published by the Free Software
-Foundation; version 2 of the License.
-
-This program is distributed in the hope that it will be useful, but WITHOUT
-ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
-FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.
-
-You should have received a copy of the GNU General Public License along with
-this program; if not, write to the Free Software Foundation, Inc.,
-51 Franklin Street, Suite 500, Boston, MA 02110-1335 USA
-
-*****************************************************************************/
-
-/**************************************************//**
-@file include/usr0sess.h
-Sessions
-
-Created 6/25/1996 Heikki Tuuri
-*******************************************************/
-
-#ifndef usr0sess_h
-#define usr0sess_h
-
-#include "univ.i"
-#include "ut0byte.h"
-#include "trx0types.h"
-#include "srv0srv.h"
-#include "trx0types.h"
-#include "usr0types.h"
-#include "que0types.h"
-#include "data0data.h"
-#include "rem0rec.h"
-
-/*********************************************************************//**
-Opens a session.
-@return own: session object */
-sess_t*
-sess_open(void);
-/*============*/
-/*********************************************************************//**
-Closes a session, freeing the memory occupied by it. */
-void
-sess_close(
-/*=======*/
-	sess_t*		sess);		/* in, own: session object */
-
-/* The session handle. This data structure is only used by purge and is
-not really necessary. We should get rid of it. */
-struct sess_t{
-	ulint		state;		/*!< state of the session */
-	trx_t*		trx;		/*!< transaction object permanently
-					assigned for the session: the
-					transaction instance designated by the
-					trx id changes, but the memory
-					structure is preserved */
-};
-
-/* Session states */
-#define SESS_ACTIVE		1
-#define SESS_ERROR		2	/* session contains an error message
-					which has not yet been communicated
-					to the client */
-#endif

storage/innobase/include/usr0types.h

-/*****************************************************************************
-
-Copyright (c) 1996, 2009, Oracle and/or its affiliates. All Rights Reserved.
-
-This program is free software; you can redistribute it and/or modify it under
-the terms of the GNU General Public License as published by the Free Software
-Foundation; version 2 of the License.
-
-This program is distributed in the hope that it will be useful, but WITHOUT
-ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
-FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.
-
-You should have received a copy of the GNU General Public License along with
-this program; if not, write to the Free Software Foundation, Inc.,
-51 Franklin Street, Suite 500, Boston, MA 02110-1335 USA
-
-*****************************************************************************/
-
-/**************************************************//**
-@file include/usr0types.h
-Users and sessions global types
-
-Created 6/25/1996 Heikki Tuuri
-*******************************************************/
-
-#ifndef usr0types_h
-#define usr0types_h
-
-struct sess_t;
-
-#endif

storage/innobase/lock/lock0lock.cc

@@ -35,7 +35,6 @@ Created 5/7/1996 Heikki Tuuri
 #include "lock0lock.h"
 #include "lock0priv.h"
 #include "dict0mem.h"
-#include "usr0sess.h"
 #include "trx0purge.h"
 #include "trx0sys.h"
 #include "srv0mon.h"

storage/innobase/lock/lock0prdt.cc

@@ -29,7 +29,6 @@ Created 9/7/2013 Jimmy Yang
 #include "lock0priv.h"
 #include "lock0prdt.h"
 #include "ha_prototypes.h"
-#include "usr0sess.h"
 #include "trx0purge.h"
 #include "dict0mem.h"
 #include "dict0boot.h"

storage/innobase/que/que0que.cc

 /*****************************************************************************
 
 Copyright (c) 1996, 2016, Oracle and/or its affiliates. All Rights Reserved.
-Copyright (c) 2017, MariaDB Corporation.
+Copyright (c) 2017, 2018, MariaDB Corporation.
 
 This program is free software; you can redistribute it and/or modify it under
 the terms of the GNU General Public License as published by the Free Software
@@ -27,7 +27,6 @@ Created 5/27/1996 Heikki Tuuri
 #include "ha_prototypes.h"
 
 #include "que0que.h"
-#include "usr0sess.h"
 #include "trx0trx.h"
 #include "trx0roll.h"
 #include "row0undo.h"

storage/innobase/row/row0ins.cc

@@ -45,7 +45,6 @@ Created 4/20/1996 Heikki Tuuri
 #include "log0log.h"
 #include "eval0eval.h"
 #include "data0data.h"
-#include "usr0sess.h"
 #include "buf0lru.h"
 #include "fts0fts.h"
 #include "fts0types.h"

storage/innobase/srv/srv0srv.cc

@@ -3,7 +3,7 @@
 Copyright (c) 1995, 2017, Oracle and/or its affiliates. All Rights Reserved.
 Copyright (c) 2008, 2009 Google Inc.
 Copyright (c) 2009, Percona Inc.
-Copyright (c) 2013, 2017, MariaDB Corporation.
+Copyright (c) 2013, 2018, MariaDB Corporation.
 
 Portions of this file contain modifications contributed and copyrighted by
 Google, Inc. Those modifications are gratefully acknowledged and are described
@@ -70,7 +70,6 @@ Created 10/8/1995 Heikki Tuuri
 #include "sync0sync.h"
 #include "trx0i_s.h"
 #include "trx0purge.h"
-#include "usr0sess.h"
 #include "ut0crc32.h"
 #include "btr0defragment.h"
 #include "ut0mem.h"

storage/innobase/srv/srv0start.cc

@@ -88,7 +88,6 @@ Created 2/16/1996 Heikki Tuuri
 #include "dict0load.h"
 #include "dict0stats_bg.h"
 #include "que0que.h"
-#include "usr0sess.h"
 #include "lock0lock.h"
 #include "trx0roll.h"
 #include "trx0purge.h"

storage/innobase/trx/trx0purge.cc

 /*****************************************************************************
 
 Copyright (c) 1996, 2017, Oracle and/or its affiliates. All Rights Reserved.
-Copyright (c) 2017, MariaDB Corporation.
+Copyright (c) 2017, 2018, MariaDB Corporation.
 
 This program is free software; you can redistribute it and/or modify it under
 the terms of the GNU General Public License as published by the Free Software
@@ -165,21 +165,15 @@ TrxUndoRsegsIterator::set_next()
 
 /** Build a purge 'query' graph. The actual purge is performed by executing
 this query graph.
-@param[in,out]	sess	the purge session
 @return own: the query graph */
 static
 que_t*
-trx_purge_graph_build(sess_t* sess)
+purge_graph_build()
 {
 	ut_a(srv_n_purge_threads > 0);
-	/* A purge transaction is not a real transaction, we use a transaction
-	here only because the query threads code requires it. It is otherwise
-	quite unnecessary. We should get rid of it eventually. */
-	trx_t* trx = sess->trx;
 
-	ut_ad(trx->sess == sess);
-
-	trx->id = 0;
+	trx_t* trx = trx_allocate_for_background();
+	ut_ad(!trx->id);
 	trx->start_time = ut_time();
 	trx->state = TRX_STATE_ACTIVE;
 	trx->op_info = "purge trx";
@@ -199,9 +193,9 @@ trx_purge_graph_build(sess_t* sess)
 
 /** Construct the purge system. */
 purge_sys_t::purge_sys_t()
-	: sess(sess_open()), latch(), event(os_event_create(0)),
+	: latch(), event(os_event_create(0)),
 	  n_stop(0), running(false), state(PURGE_STATE_INIT),
-	  query(trx_purge_graph_build(sess)),
+	  query(purge_graph_build()),
 	  view(), n_submitted(0), n_completed(0),
 	  iter(), limit(),
 #ifdef UNIV_DEBUG
@@ -221,10 +215,12 @@ purge_sys_t::~purge_sys_t()
 {
 	ut_ad(this == purge_sys);
 
+	trx_t* trx = query->trx;
 	que_graph_free(query);
-	ut_a(sess->trx->id == 0);
-	sess->trx->state = TRX_STATE_NOT_STARTED;
-	sess_close(sess);
+	ut_ad(!trx->id);
+	ut_ad(trx->state == TRX_STATE_ACTIVE);
+	trx->state = TRX_STATE_NOT_STARTED;
+	trx_free_for_background(trx);
 	view.close();
 	rw_lock_free(&latch);
 	/* rw_lock_free() already called latch.~rw_lock_t(); tame the

storage/innobase/trx/trx0roll.cc

@@ -47,7 +47,6 @@ Created 3/26/1996 Heikki Tuuri
 #include "trx0sys.h"
 #include "trx0trx.h"
 #include "trx0undo.h"
-#include "usr0sess.h"
 #include "ha_prototypes.h"
 
 /** This many pages must be undone before a truncate is tried within

storage/innobase/trx/trx0sys.cc

@@ -500,8 +500,6 @@ trx_sys_init_at_db_start()
 	mtr.commit();
 	ut_d(trx_sys->rw_max_trx_id = trx_sys->max_trx_id);
 
-	trx_dummy_sess = sess_open();
-
 	trx_lists_init_at_db_start();
 
 	/* This mutex is not strictly required, it is here only to satisfy
@@ -928,11 +926,6 @@ trx_sys_close(void)
 			" shutdown: " << size << " read views open";
 	}
 
-	if (trx_dummy_sess) {
-		sess_close(trx_dummy_sess);
-		trx_dummy_sess = NULL;
-	}
-
 	/* Only prepared transactions may be left in the system. Free them. */
 	ut_a(UT_LIST_GET_LEN(trx_sys->rw_trx_list) == trx_sys->n_prepared_trx
 	     || !srv_was_started

storage/innobase/trx/trx0trx.cc

@@ -51,7 +51,6 @@ Created 3/26/1996 Heikki Tuuri
 #include "trx0rseg.h"
 #include "trx0undo.h"
 #include "trx0xa.h"
-#include "usr0sess.h"
 #include "ut0new.h"
 #include "ut0pool.h"
 #include "ut0vec.h"
@@ -70,9 +69,6 @@ typedef std::set<
 	std::less<table_id_t>,
 	ut_allocator<table_id_t> >	table_id_set;
 
-/** Dummy session used currently in MySQL interface */
-sess_t*	trx_dummy_sess = NULL;
-
 /** Constructor */
 TrxVersion::TrxVersion(trx_t* trx)
 	:
@@ -518,8 +514,6 @@ trx_allocate_for_background(void)
 
 	trx = trx_create_low();
 
-	trx->sess = trx_dummy_sess;
-
 	return(trx);
 }
 

storage/innobase/usr/usr0sess.cc

-/*****************************************************************************
-
-Copyright (c) 1996, 2016, Oracle and/or its affiliates. All Rights Reserved.
-Copyright (c) 2017, MariaDB Corporation.
-
-This program is free software; you can redistribute it and/or modify it under
-the terms of the GNU General Public License as published by the Free Software
-Foundation; version 2 of the License.
-
-This program is distributed in the hope that it will be useful, but WITHOUT
-ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
-FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.
-
-You should have received a copy of the GNU General Public License along with
-this program; if not, write to the Free Software Foundation, Inc.,
-51 Franklin Street, Suite 500, Boston, MA 02110-1335 USA
-
-*****************************************************************************/
-
-/**************************************************//**
-@file usr/usr0sess.cc
-Sessions
-
-Created 6/25/1996 Heikki Tuuri
-*******************************************************/
-
-#include "usr0sess.h"
-#include "trx0trx.h"
-
-/*********************************************************************//**
-Opens a session.
-@return own: session object */
-sess_t*
-sess_open(void)
-/*===========*/
-{
-	sess_t*	sess;
-
-	sess = static_cast<sess_t*>(ut_zalloc_nokey(sizeof(*sess)));
-
-	sess->state = SESS_ACTIVE;
-
-	sess->trx = trx_allocate_for_background();
-	sess->trx->sess = sess;
-
-	return(sess);
-}
-
-/*********************************************************************//**
-Closes a session, freeing the memory occupied by it. */
-void
-sess_close(
-/*=======*/
-	sess_t*	sess)	/*!< in, own: session object */
-{
-	trx_free_for_background(sess->trx);
-	ut_free(sess);
-}

storage/innobase/ut/ut0new.cc

@@ -167,7 +167,6 @@ ut_new_boot()
 		"trx0sys",
 		"trx0trx",
 		"trx0undo",
-		"usr0sess",
 		"ut0list",
 		"ut0mem",
 		"ut0mutex",