MDEV-15019 - InnoDB: store ReadView on trx

This will allow us to reduce critical section protected by
trx_sys.mutex:
- no need to maintain global m_free list
- eliminate if (trx->read_view == NULL) condition.

On x86_64 sizeof(Readview) is 144 mostly due to padding, sizeof(trx_t)
with ReadView is 1200.

Also don't close ReadView for read-write transactions, just mark it
closed similarly to read-only.

Clean-up: removed n_prepared_recovered_trx and n_prepared_trx, which
accidentally re-appeared after some rebase.

storage/innobase/handler/ha_innodb.cc

@@ -3503,7 +3503,7 @@ ha_innobase::init_table_handle_for_HANDLER(void)
 
 	/* Assign a read view if the transaction does not have it yet */
 
-	trx_assign_read_view(m_prebuilt->trx);
+	trx_sys.mvcc.view_open(m_prebuilt->trx);
 
 	innobase_register_trx(ht, m_user_thd, m_prebuilt->trx);
 
@@ -4394,7 +4394,7 @@ innobase_start_trx_and_assign_read_view(
 		thd_get_trx_isolation(thd));
 
 	if (trx->isolation_level == TRX_ISO_REPEATABLE_READ) {
-		trx_assign_read_view(trx);
+		trx_sys.mvcc.view_open(trx);
 	} else {
 		push_warning_printf(thd, Sql_condition::WARN_LEVEL_WARN,
 				    HA_ERR_UNSUPPORTED,
@@ -16220,7 +16220,7 @@ ha_innobase::external_lock(
 			}
 
 		} else if (trx->isolation_level <= TRX_ISO_READ_COMMITTED
-			   && MVCC::is_view_active(trx->read_view)) {
+			   && trx->read_view.is_open()) {
 			mutex_enter(&trx_sys.mutex);
 			trx_sys.mvcc.view_close(trx->read_view);
 			mutex_exit(&trx_sys.mutex);
@@ -16885,7 +16885,7 @@ ha_innobase::store_lock(
 			(enum_tx_isolation) thd_tx_isolation(thd));
 
 		if (trx->isolation_level <= TRX_ISO_READ_COMMITTED
-		    && MVCC::is_view_active(trx->read_view)) {
+		    && trx->read_view.is_open()) {
 
 			/* At low transaction isolation levels we let
 			each consistent read set its own snapshot */

storage/innobase/handler/handler0alter.cc

@@ -5562,7 +5562,7 @@ error_handling_drop_uncached:
 	if (ctx->online && ctx->num_to_add_index) {
 		/* Assign a consistent read view for
 		row_merge_read_clustered_index(). */
-		trx_assign_read_view(ctx->prebuilt->trx);
+		trx_sys.mvcc.view_open(ctx->prebuilt->trx);
 	}
 
 	if (fts_index) {

storage/innobase/include/read0read.h

@@ -31,60 +31,51 @@ Created 2/16/1997 Heikki Tuuri
 #include "read0types.h"
 
 /** The MVCC read view manager */
-class MVCC {
+class MVCC
+{
+  /** Active views. */
+  UT_LIST_BASE_NODE_T(ReadView) m_views;
+
+
+  /** Validates a read view list. */
+  bool validate() const;
 public:
-	/** Constructor
+  MVCC() { UT_LIST_INIT(m_views, &ReadView::m_view_list); }
-	@param size		Number of views to pre-allocate */
+  ~MVCC() { ut_ad(UT_LIST_GET_LEN(m_views) == 0); }
-	void create(ulint size);
 
-	/** Destructor.
-	Free all the views in the m_free list */
-	void close();
 
-	/**
+  /**
-	Allocate and create a view.
+    Allocate and create a view.
-	@param view		view owned by this class created for the
+    @param trx transaction creating the view
-				caller. Must be freed by calling close()
+  */
-	@param trx		transaction creating the view */
+  void view_open(trx_t *trx);
-	void view_open(ReadView*& view, trx_t* trx);
 
-	/**
-	Close a view created by the above function.
-	@param view		view allocated by trx_open. */
-	void view_close(ReadView*& view);
 
-	/** Clones the oldest view and stores it in view. No need to
+  /**
-	call view_close(). The caller owns the view that is passed in.
+    Close a view created by the above function.
-	It will also move the closed views from the m_views list to the
+    @param view view allocated by view_open.
-	m_free list. This function is called by Purge to create it view.
+  */
-	@param view		Preallocated view, owned by the caller */
+  void view_close(ReadView &view)
-	void clone_oldest_view(ReadView* view);
+  {
+    view.close();
+    view.set_registered(false);
+    UT_LIST_REMOVE(m_views, &view);
+    ut_ad(validate());
+  }
 
-	/**
-	@return the number of active views */
-	ulint size() const;
 
-	/**
+  /**
-	@return true if the view is active and valid */
+    Clones the oldest view and stores it in view. No need to
-	static bool is_view_active(ReadView* view)
+    call view_close(). The caller owns the view that is passed in.
-	{
+    This function is called by Purge to create it view.
-		return view && !view->is_closed();
-	}
 
-private:
+    @param view Preallocated view, owned by the caller
+  */
+  void clone_oldest_view(ReadView *view);
 
-	/**
-	Validates a read view list. */
-	bool validate() const;
 
-	typedef UT_LIST_BASE_NODE_T(ReadView) view_list_t;
+  /** @return the number of active views */
-
+  size_t size() const;
-	/** Free views ready for reuse. */
-	view_list_t		m_free;
-
-	/** Active and closed views, the closed views will have the
-	creator trx id set to TRX_ID_MAX */
-	view_list_t		m_views;
 };
 
 #endif /* read0read_h */

storage/innobase/include/read0types.h

@@ -198,19 +198,13 @@ public:
 	{
 		ut_ad(m_creator_trx_id != TRX_ID_MAX);
 		m_creator_trx_id = TRX_ID_MAX;
+		set_open(false);
 	}
 
-	/**
+	bool is_open() const { return(m_open); }
-	@return true if the view is closed */
+	void set_open(bool open) { m_open= open; }
-	bool is_closed() const
+	bool is_registered() const { return(m_registered); }
-	{
+	void set_registered(bool registered) { m_registered= registered; }
-		return(m_closed);
-	}
-
-	void set_closed(bool closed)
-	{
-		m_closed= closed;
-	}
 
 	/**
 	Write the limits to the file.
@@ -325,14 +319,15 @@ private:
 	they can be removed in purge if not needed by other views */
 	trx_id_t	m_low_limit_no;
 
-	/** AC-NL-RO transaction view that has been "closed". */
+	/** true if view is open. */
-	bool		m_closed;
+	bool		m_open;
 
-	typedef UT_LIST_NODE_T(ReadView) node_t;
+	/** true if transaction is in MVCC::m_views. Only thread that owns
+	this view may access it. */
+	bool		m_registered;
 
-	/** List of read views in trx_sys */
+	byte		pad1[CACHE_LINE_SIZE];
-	byte		pad1[64 - sizeof(node_t)];
+	UT_LIST_NODE_T(ReadView)	m_view_list;
-	node_t		m_view_list;
 };
 
 #endif

storage/innobase/include/trx0sys.h

@@ -883,17 +883,6 @@ public:
 
   MY_ALIGNED(CACHE_LINE_SIZE) rw_trx_hash_t rw_trx_hash;
 
-	ulint		n_prepared_trx;	/*!< Number of transactions currently
-					in the XA PREPARED state */
-
-	ulint		n_prepared_recovered_trx; /*!< Number of transactions
-					currently in XA PREPARED state that are
-					also recovered. Such transactions cannot
-					be added during runtime. They can only
-					occur after recovery if mysqld crashed
-					while there were XA PREPARED
-					transactions. We disable query cache
-					if such transactions exist. */
 
   /**
     Constructor.

storage/innobase/include/trx0trx.h

@@ -45,13 +45,11 @@ Created 3/26/1996 Heikki Tuuri
 #include "ut0vec.h"
 #include "fts0fts.h"
 #include "srv0srv.h"
+#include "read0types.h"
 
 // Forward declaration
 struct mtr_t;
 
-// Forward declaration
-class ReadView;
-
 // Forward declaration
 class FlushObserver;
 
@@ -290,23 +288,6 @@ void
 trx_mark_sql_stat_end(
 /*==================*/
 	trx_t*	trx);	/*!< in: trx handle */
-/********************************************************************//**
-Assigns a read view for a consistent read query. All the consistent reads
-within the same transaction will get the same read view, which is created
-when this function is first called for a new started transaction. */
-ReadView*
-trx_assign_read_view(
-/*=================*/
-	trx_t*	trx);	/*!< in: active transaction */
-
-/****************************************************************//**
-@return the transaction's read view or NULL if one not assigned. */
-UNIV_INLINE
-ReadView*
-trx_get_read_view(
-/*==============*/
-	trx_t*	trx);
-
 /****************************************************************//**
 Prepares a transaction for commit/rollback. */
 void
@@ -571,7 +552,7 @@ Check transaction state */
 	ut_ad(trx_state_eq((t), TRX_STATE_NOT_STARTED)			\
 	      || trx_state_eq((t), TRX_STATE_FORCED_ROLLBACK));		\
 	ut_ad(!trx->has_logged());					\
-	ut_ad(!MVCC::is_view_active((t)->read_view));			\
+	ut_ad(!(t)->read_view.is_open());				\
 	ut_ad((t)->lock.wait_thr == NULL);				\
 	ut_ad(UT_LIST_GET_LEN((t)->lock.trx_locks) == 0);		\
 	ut_ad((t)->dict_operation == TRX_DICT_OP_NONE);			\
@@ -1000,7 +981,7 @@ public:
 
 	trx_state_t	state;
 
-	ReadView*	read_view;	/*!< consistent read view used in the
+	ReadView	read_view;	/*!< consistent read view used in the
 					transaction, or NULL if not yet set */
 
 	UT_LIST_NODE_T(trx_t)

storage/innobase/include/trx0trx.ic

@@ -211,17 +211,6 @@ ok:
 	trx->dict_operation = op;
 }
 
-/**
-@param trx		Get the active view for this transaction, if one exists
-@return the transaction's read view or NULL if one not assigned. */
-UNIV_INLINE
-ReadView*
-trx_get_read_view(
-	trx_t*		trx)
-{
-	return(!MVCC::is_view_active(trx->read_view) ? NULL : trx->read_view);
-}
-
 /**
 @param[in] trx		Transaction to check
 @return true if the transaction is a high priority transaction.*/

storage/innobase/lock/lock0lock.cc

@@ -415,7 +415,8 @@ lock_clust_rec_cons_read_sees(
 	operate on same temp-table and so read of temp-table is
 	always consistent read. */
 	if (srv_read_only_mode || dict_table_is_temporary(index->table)) {
-		ut_ad(view == 0 || dict_table_is_temporary(index->table));
+		ut_ad(!view->is_open()
+		      || dict_table_is_temporary(index->table));
 		return(true);
 	}
 
@@ -5719,15 +5720,13 @@ lock_trx_print_wait_and_mvcc_state(
 
 	trx_print_latched(file, trx, 600);
 
-	/* Note: this read_view access is data race. Further
+	/* Note: read_view->is_active() check is race condition. But it
-	read_view->is_active() check is race condition. But it should
+	should "kind of work" because read_view is freed only at shutdown.
-	"kind of work" because read_view is freed only at shutdown.
 	Worst thing that may happen is that it'll get transferred to
 	another thread and print wrong values. */
-	const ReadView*	read_view = trx->read_view;
 
-	if (read_view != NULL && !read_view->is_closed()) {
+	if (trx->read_view.is_open()) {
-		read_view->print_limits(file);
+		trx->read_view.print_limits(file);
 	}
 
 	if (trx->lock.que_state == TRX_QUE_LOCK_WAIT) {

storage/innobase/read/read0read.cc

@@ -182,8 +182,9 @@ struct	ViewCheck {
 
 	void	operator()(const ReadView* view)
 	{
+		ut_ad(view->is_registered());
 		ut_a(m_prev_view == NULL
-		     || view->is_closed()
+		     || !view->is_open()
 		     || view->le(m_prev_view));
 
 		m_prev_view = view;
@@ -325,7 +326,9 @@ ReadView::ReadView()
 	m_up_limit_id(),
 	m_creator_trx_id(),
 	m_ids(),
-	m_low_limit_no()
+	m_low_limit_no(),
+	m_open(false),
+	m_registered(false)
 {
 	ut_d(::memset(&m_view_list, 0x0, sizeof(m_view_list)));
 }
@@ -337,34 +340,6 @@ ReadView::~ReadView()
 	// Do nothing
 }
 
-/** Constructor
-@param size		Number of views to pre-allocate */
-void MVCC::create(ulint size)
-{
-	UT_LIST_INIT(m_free, &ReadView::m_view_list);
-	UT_LIST_INIT(m_views, &ReadView::m_view_list);
-
-	for (ulint i = 0; i < size; ++i) {
-		ReadView*	view = UT_NEW_NOKEY(ReadView());
-
-		UT_LIST_ADD_FIRST(m_free, view);
-	}
-}
-
-void MVCC::close()
-{
-	for (ReadView* view = UT_LIST_GET_FIRST(m_free);
-	     view != NULL;
-	     view = UT_LIST_GET_FIRST(m_free)) {
-
-		UT_LIST_REMOVE(m_free, view);
-
-		UT_DELETE(view);
-	}
-
-	ut_a(UT_LIST_GET_LEN(m_views) == 0);
-}
-
 /**
 Copy the transaction ids from the source vector */
 
@@ -488,76 +463,89 @@ ReadView::complete()
 	m_up_limit_id = !m_ids.empty() ? m_ids.front() : m_low_limit_id;
 
 	ut_ad(m_up_limit_id <= m_low_limit_id);
-
+	set_open(true);
-	m_closed = false;
 }
 
+
 /**
-Allocate and create a view.
+  Create a view.
-@param view		view owned by this class created for the
+
-			caller. Must be freed by calling view_close()
+  Assigns a read view for a consistent read query. All the consistent reads
-@param trx		transaction instance of caller */
+  within the same transaction will get the same read view, which is created
-void
+  when this function is first called for a new started transaction.
-MVCC::view_open(ReadView*& view, trx_t* trx)
+
+  @param trx   transaction instance of caller
+*/
+
+void MVCC::view_open(trx_t* trx)
 {
-	ut_ad(!srv_read_only_mode);
+  if (srv_read_only_mode)
+  {
+    ut_ad(!trx->read_view.is_open());
+    return;
+  }
+  else if (trx->read_view.is_open())
+    return;
 
-	/** If no new RW transaction has been started since the last view
+  /*
-	was created then reuse the the existing view. */
+    Reuse closed view if there were no read-write transactions since (and at) it's
-	if (view != NULL) {
+    creation time.
+  */
+  if (trx->read_view.is_registered() &&
+      trx_is_autocommit_non_locking(trx) &&
+      trx->read_view.empty() &&
+      trx->read_view.m_low_limit_id == trx_sys.get_max_trx_id())
+  {
+    /*
+      Original comment states: there is an inherent race here between purge
+      and this thread.
 
-		uintptr_t	p = reinterpret_cast<uintptr_t>(view);
+      To avoid this race we should've checked trx_sys.get_max_trx_id() and
+      do trx->read_view.set_open(true) atomically under trx_sys.mutex
+      protection. But we're cutting edges to achieve great scalability.
 
-		view = reinterpret_cast<ReadView*>(p & ~1);
+      There're at least two types of concurrent threads interested in this
+      value: purge coordinator thread (see MVCC::clone_oldest_view()) and
+      InnoDB monitor thread (see lock_trx_print_wait_and_mvcc_state()).
 
-		ut_ad(view->m_closed);
+      What bad things can happen because we allow this race?
 
-		/* NOTE: This can be optimised further, for now we only
+      First, purge thread may be affected by this race condition only if this
-		resuse the view iff there are no active RW transactions.
+      view is the oldest open view. In other words this view is either last in
+      m_views list or there're no open views beyond.
 
-		There is an inherent race here between purge and this
+      In this case purge may not catch this view and clone some younger view
-		thread. Purge will skip views that are marked as closed.
+      instead. It might be kind of alright, because there were no read-write
-		Therefore we must set the low limit id after we reset the
+      transactions and there should be nothing to purge. Besides younger view
-		closed status after the check. */
+      must have exactly the same values.
 
-		if (trx_is_autocommit_non_locking(trx) && view->empty()) {
+      Second, scary things start when there's a read-write transaction starting
+      concurrently.
 
-			view->m_closed = false;
+      Speculative execution may reorder set_open() before get_max_trx_id(). In
+      this case purge thread has short gap to clone outdated view. Which is
+      probably not that bad: it just won't be able to purge things that it was
+      actually allowed to purge for a short while.
 
-			if (view->m_low_limit_id == trx_sys.get_max_trx_id()) {
+      This thread may as well get suspended after trx_sys.get_max_trx_id() and
-				return;
+      before trx->read_view.set_open(true). New read-write transaction may get
-			} else {
+      started, committed and purged meanwhile. It is acceptable as well, since
-				view->m_closed = true;
+      this view doesn't see it.
-			}
+    */
-		}
+    trx->read_view.set_open(true);
+    return;
+  }
 
-		mutex_enter(&trx_sys.mutex);
+  mutex_enter(&trx_sys.mutex);
-
+  trx->read_view.prepare(trx->id);
-		UT_LIST_REMOVE(m_views, view);
+  trx->read_view.complete();
-
+  if (trx->read_view.is_registered())
-	} else {
+    UT_LIST_REMOVE(m_views, &trx->read_view);
-		mutex_enter(&trx_sys.mutex);
+  else
-		if ((view = UT_LIST_GET_FIRST(m_free))) {
+    trx->read_view.set_registered(true);
-			UT_LIST_REMOVE(m_free, view);
+  UT_LIST_ADD_FIRST(m_views, &trx->read_view);
-		} else if (!(view = UT_NEW_NOKEY(ReadView()))) {
+  ut_ad(validate());
-			ib::error() << "Failed to allocate MVCC view";
+  mutex_exit(&trx_sys.mutex);
-		}
-	}
-
-	if (view != NULL) {
-
-		view->prepare(trx->id);
-
-		view->complete();
-
-		UT_LIST_ADD_FIRST(m_views, view);
-
-		ut_ad(!view->is_closed());
-
-		ut_ad(validate());
-	}
-
-	mutex_exit(&trx_sys.mutex);
 }
 
 /**
@@ -625,7 +613,7 @@ MVCC::clone_oldest_view(ReadView* view)
 	     oldest_view != NULL;
 	     oldest_view = UT_LIST_GET_PREV(m_view_list, oldest_view))
 	{
-		if (!oldest_view->is_closed())
+		if (oldest_view->is_open())
 		{
 			view->copy_prepare(*oldest_view);
 			mutex_exit(&trx_sys.mutex);
@@ -642,18 +630,18 @@ MVCC::clone_oldest_view(ReadView* view)
 /**
 @return the number of active views */
 
-ulint
+size_t
 MVCC::size() const
 {
 	mutex_enter(&trx_sys.mutex);
 
-	ulint	size = 0;
+	size_t	size = 0;
 
 	for (const ReadView* view = UT_LIST_GET_FIRST(m_views);
 	     view != NULL;
 	     view = UT_LIST_GET_NEXT(m_view_list, view)) {
 
-		if (!view->is_closed()) {
+		if (view->is_open()) {
 			++size;
 		}
 	}
@@ -662,18 +650,3 @@ MVCC::size() const
 
 	return(size);
 }
-
-/**
-Close a view created by the above function.
-@param view		view allocated by trx_open. */
-
-void
-MVCC::view_close(ReadView*& view)
-{
-	ut_ad(mutex_own(&trx_sys.mutex));
-	view->close();
-	UT_LIST_REMOVE(m_views, view);
-	UT_LIST_ADD_LAST(m_free, view);
-	ut_ad(validate());
-	view = NULL;
-}

storage/innobase/row/row0merge.cc

@@ -2101,16 +2101,16 @@ end_of_index:
 			ONLINE_INDEX_COMPLETE state between the time
 			the DML thread has updated the clustered index
 			but has not yet accessed secondary index. */
-			ut_ad(MVCC::is_view_active(trx->read_view));
+			ut_ad(trx->read_view.is_open());
 			ut_ad(rec_trx_id != trx->id);
 
-			if (!trx->read_view->changes_visible(
+			if (!trx->read_view.changes_visible(
 				    rec_trx_id, old_table->name)) {
 				rec_t*	old_vers;
 
 				row_vers_build_for_consistent_read(
 					rec, &mtr, clust_index, &offsets,
-					trx->read_view, &row_heap,
+					&trx->read_view, &row_heap,
 					row_heap, &old_vers, NULL);
 
 				if (!old_vers) {
@@ -4526,8 +4526,8 @@ row_merge_is_index_usable(
 	return(!dict_index_is_corrupted(index)
 	       && (dict_table_is_temporary(index->table)
 		   || index->trx_id == 0
-		   || !MVCC::is_view_active(trx->read_view)
+		   || !trx->read_view.is_open()
-		   || trx->read_view->changes_visible(
+		   || trx->read_view.changes_visible(
 			   index->trx_id,
 			   index->table->name)));
 }

storage/innobase/row/row0sel.cc

@@ -2268,15 +2268,11 @@ row_sel_step(
 		plan_reset_cursor(sel_node_get_nth_plan(node, 0));
 
 		if (node->consistent_read) {
+			trx_t *trx = thr_get_trx(thr);
 			/* Assign a read view for the query */
-			trx_assign_read_view(thr_get_trx(thr));
+			trx_sys.mvcc.view_open(trx);
-
+			node->read_view = trx->read_view.is_open() ?
-			if (thr_get_trx(thr)->read_view != NULL) {
+					  &trx->read_view : NULL;
-				node->read_view = thr_get_trx(thr)->read_view;
-			} else {
-				node->read_view = NULL;
-			}
-
 		} else {
 			sym_node_t*	table_node;
 			lock_mode	i_lock_mode;
@@ -3440,12 +3436,12 @@ row_sel_get_clust_rec_for_mysql(
 		if (trx->isolation_level > TRX_ISO_READ_UNCOMMITTED
 		    && !lock_clust_rec_cons_read_sees(
 			    clust_rec, clust_index, *offsets,
-			    trx_get_read_view(trx))) {
+			    &trx->read_view)) {
 
 			/* The following call returns 'offsets' associated with
 			'old_vers' */
 			err = row_sel_build_prev_vers_for_mysql(
-				trx->read_view, clust_index, prebuilt,
+				&trx->read_view, clust_index, prebuilt,
 				clust_rec, offsets, offset_heap, &old_vers,
 				vrow, mtr);
 
@@ -3864,8 +3860,8 @@ exhausted:
 	*offsets = rec_get_offsets(rec, index, *offsets, true,
 				   ULINT_UNDEFINED, heap);
 
-	if (!lock_clust_rec_cons_read_sees(
+	if (!lock_clust_rec_cons_read_sees(rec, index, *offsets,
-			rec, index, *offsets, trx_get_read_view(trx))) {
+					   &trx->read_view)) {
 		goto retry;
 	}
 
@@ -4269,7 +4265,7 @@ row_search_mvcc(
 
 		if (prebuilt->select_lock_type == LOCK_NONE
 		    && trx->isolation_level > TRX_ISO_READ_UNCOMMITTED
-		    && MVCC::is_view_active(trx->read_view)) {
+		    && trx->read_view.is_open()) {
 
 			/* This is a SELECT query done as a consistent read,
 			and the read view has already been allocated:
@@ -4367,7 +4363,7 @@ row_search_mvcc(
 
 	ut_ad(prebuilt->sql_stat_start
 	      || prebuilt->select_lock_type != LOCK_NONE
-	      || MVCC::is_view_active(trx->read_view)
+	      || trx->read_view.is_open()
 	      || prebuilt->table->no_rollback()
 	      || srv_read_only_mode);
 
@@ -4414,7 +4410,7 @@ row_search_mvcc(
 	} else if (!prebuilt->sql_stat_start) {
 		/* No need to set an intention lock or assign a read view */
 
-		if (!MVCC::is_view_active(trx->read_view)
+		if (!trx->read_view.is_open()
 		    && !srv_read_only_mode
 		    && prebuilt->select_lock_type == LOCK_NONE) {
 
@@ -4430,9 +4426,7 @@ row_search_mvcc(
 		/* Assign a read view for the query */
 		trx_start_if_not_started(trx, false);
 
-		if (!srv_read_only_mode) {
+		trx_sys.mvcc.view_open(trx);
-			trx_assign_read_view(trx);
-		}
 
 		prebuilt->sql_stat_start = FALSE;
 	} else {
@@ -5036,14 +5030,13 @@ no_gap_lock:
 
 			if (srv_force_recovery < 5
 			    && !lock_clust_rec_cons_read_sees(
-				    rec, index, offsets,
+				    rec, index, offsets, &trx->read_view)) {
-				    trx_get_read_view(trx))) {
 
 				rec_t*	old_vers;
 				/* The following call returns 'offsets'
 				associated with 'old_vers' */
 				err = row_sel_build_prev_vers_for_mysql(
-					trx->read_view, clust_index,
+					&trx->read_view, clust_index,
 					prebuilt, rec, &offsets, &heap,
 					&old_vers, need_vrow ? &vrow : NULL,
 					&mtr);
@@ -5073,7 +5066,7 @@ no_gap_lock:
 
 			if (!srv_read_only_mode
 			    && !lock_sec_rec_cons_read_sees(
-					rec, index, trx->read_view)) {
+					rec, index, &trx->read_view)) {
 				/* We should look at the clustered index.
 				However, as this is a non-locking read,
 				we can skip the clustered index lookup if
@@ -5877,18 +5870,16 @@ row_search_check_if_query_cache_permitted(
 
 	const bool ret = lock_table_get_n_locks(table) == 0
 		&& ((trx->id != 0 && trx->id >= table->query_cache_inv_id)
-		    || !MVCC::is_view_active(trx->read_view)
+		    || !trx->read_view.is_open()
-		    || trx->read_view->low_limit_id()
+		    || trx->read_view.low_limit_id()
 		    >= table->query_cache_inv_id);
 	if (ret) {
 		/* If the isolation level is high, assign a read view for the
 		transaction if it does not yet have one */
 
-		if (trx->isolation_level >= TRX_ISO_REPEATABLE_READ
+		if (trx->isolation_level >= TRX_ISO_REPEATABLE_READ) {
-		    && !srv_read_only_mode
-		    && !MVCC::is_view_active(trx->read_view)) {
 
-			trx_sys.mvcc.view_open(trx->read_view, trx);
+			trx_sys.mvcc.view_open(trx);
 		}
 	}
 

storage/innobase/trx/trx0sys.cc

@@ -459,8 +459,6 @@ trx_sys_t::create()
 	UT_LIST_INIT(serialisation_list, &trx_t::no_list);
 	UT_LIST_INIT(mysql_trx_list, &trx_t::mysql_trx_list);
 
-	mvcc.create(1024);
-
 	rw_trx_hash.init();
 }
 
@@ -590,8 +588,6 @@ trx_sys_t::close()
 		}
 	}
 
-	mvcc.close();
-
 	ut_a(UT_LIST_GET_LEN(mysql_trx_list) == 0);
 	ut_a(UT_LIST_GET_LEN(serialisation_list) == 0);
 

storage/innobase/trx/trx0trx.cc

@@ -192,7 +192,7 @@ trx_init(
 
 	trx->last_sql_stat_start.least_undo_no = 0;
 
-	ut_ad(!MVCC::is_view_active(trx->read_view));
+	ut_ad(!trx->read_view.is_open());
 
 	trx->lock.rec_cached = 0;
 
@@ -246,6 +246,7 @@ struct TrxFactory {
 		new(&trx->lock.table_locks) lock_pool_t();
 
 		new(&trx->hit_list) hit_list_t();
+		new(&trx->read_view) ReadView();
 
 		trx->rw_trx_hash_pins = 0;
 		trx_init(trx);
@@ -301,7 +302,7 @@ struct TrxFactory {
 
 		trx->mod_tables.~trx_mod_tables_t();
 
-		ut_ad(trx->read_view == NULL);
+		ut_ad(!trx->read_view.is_open());
 
 		if (!trx->lock.rec_pool.empty()) {
 
@@ -508,7 +509,12 @@ trx_free(trx_t*& trx)
 
 	trx->mod_tables.clear();
 
-	ut_ad(trx->read_view == NULL);
+	ut_ad(!trx->read_view.is_open());
+	if (trx->read_view.is_registered()) {
+		mutex_enter(&trx_sys.mutex);
+		trx_sys.mvcc.view_close(trx->read_view);
+		mutex_exit(&trx_sys.mutex);
+	}
 
 	/* trx locking state should have been reset before returning trx
 	to pool */
@@ -677,7 +683,7 @@ trx_disconnect_from_mysql(
 
 	UT_LIST_REMOVE(trx_sys.mysql_trx_list, trx);
 
-	if (trx->read_view != NULL) {
+	if (trx->read_view.is_open()) {
 		trx_sys.mvcc.view_close(trx->read_view);
 	}
 
@@ -1536,17 +1542,11 @@ trx_erase_lists(
 {
 	ut_ad(trx->id > 0);
 
-	if (trx->rsegs.m_redo.rseg && trx->read_view) {
-		ut_ad(!trx->read_only);
-		mutex_enter(&trx_sys.mutex);
-		trx_sys.mvcc.view_close(trx->read_view);
-	} else {
-
-		mutex_enter(&trx_sys.mutex);
-	}
-
 	if (serialised) {
+		mutex_enter(&trx_sys.mutex);
 		UT_LIST_REMOVE(trx_sys.serialisation_list, trx);
+	} else {
+		mutex_enter(&trx_sys.mutex);
 	}
 
 	trx_ids_t::iterator	it = std::lower_bound(
@@ -1574,6 +1574,8 @@ trx_commit_in_memory(
 				written */
 {
 	trx->must_flush_log_later = false;
+	trx->read_view.set_open(false);
+
 
 	if (trx_is_autocommit_non_locking(trx)) {
 		ut_ad(trx->id == 0);
@@ -1597,10 +1599,6 @@ trx_commit_in_memory(
 
 		ut_ad(trx_state_eq(trx, TRX_STATE_ACTIVE));
 
-		if (trx->read_view != NULL) {
-			trx->read_view->set_closed(true);
-		}
-
 		MONITOR_INC(MONITOR_TRX_NL_RO_COMMIT);
 
 		/* AC-NL-RO transactions can't be rolled back asynchronously. */
@@ -1629,9 +1627,6 @@ trx_commit_in_memory(
 
 		if (trx->read_only || trx->rsegs.m_redo.rseg == NULL) {
 			MONITOR_INC(MONITOR_TRX_RO_COMMIT);
-			if (trx->read_view != NULL) {
-				trx->read_view->set_closed(true);
-			}
 		} else {
 			trx_update_mod_tables_timestamp(trx);
 			MONITOR_INC(MONITOR_TRX_RW_COMMIT);
@@ -1875,30 +1870,6 @@ trx_commit(
 	trx_commit_low(trx, mtr);
 }
 
-/********************************************************************//**
-Assigns a read view for a consistent read query. All the consistent reads
-within the same transaction will get the same read view, which is created
-when this function is first called for a new started transaction.
-@return consistent read view */
-ReadView*
-trx_assign_read_view(
-/*=================*/
-	trx_t*		trx)	/*!< in/out: active transaction */
-{
-	ut_ad(trx->state == TRX_STATE_ACTIVE);
-
-	if (srv_read_only_mode) {
-
-		ut_ad(trx->read_view == NULL);
-		return(NULL);
-
-	} else if (!MVCC::is_view_active(trx->read_view)) {
-		trx_sys.mvcc.view_open(trx->read_view, trx);
-	}
-
-	return(trx->read_view);
-}
-
 /****************************************************************//**
 Prepares a transaction for commit/rollback. */
 void
@@ -2754,8 +2725,8 @@ trx_set_rw_mode(
 	trx_sys.rw_trx_ids.push_back(trx->id);
 
 	/* So that we can see our own changes. */
-	if (MVCC::is_view_active(trx->read_view)) {
+	if (trx->read_view.is_open()) {
-		trx->read_view->creator_trx_id(trx->id);
+		trx->read_view.creator_trx_id(trx->id);
 	}
 	mutex_exit(&trx_sys.mutex);
 	trx_sys.rw_trx_hash.insert(trx);