Merge 10.5 into 10.6

mysql-test/main/group_min_max.result

@@ -4204,6 +4204,30 @@ a	b	s1
 2	2	t2:t2a-null;min_t3_b:t3b-null
 3	3	t2:1;min_t3_b:3
 drop table t1,t2,t3;
+# 
+# MDEV-31380: Assertion `s->table->opt_range_condition_rows <= s->found_records' failed
+#  (assertion in 10.6+, DBL_MAX costs in 10.5)
+# 
+CREATE TABLE t1 (a INT, b INT, PRIMARY KEY(a), KEY(b)) ENGINE=InnoDB;
+INSERT INTO t1 SELECT seq, seq FROM seq_1_to_100;
+SET
+@tmp=@@optimizer_use_condition_selectivity,
+optimizer_use_condition_selectivity = 1,
+@tmp2=@@optimizer_trace,
+optimizer_trace=1;
+SELECT DISTINCT * FROM t1 WHERE a IN (1, 2);
+a	b
+1	1
+2	2
+select 
+CAST(json_value(json_extract(trace, '$**.chosen_access_method.cost'), '$[0]')
+as DOUBLE) < 1.0e100
+from information_schema.optimizer_trace;
+CAST(json_value(json_extract(trace, '$**.chosen_access_method.cost'), '$[0]')
+as DOUBLE) < 1.0e100
+1
+set optimizer_use_condition_selectivity = @tmp, optimizer_trace=@tmp2;
+drop table t1;
 #
 # End of 10.5 tests
 #

mysql-test/main/group_min_max.test

@@ -7,6 +7,7 @@
 --source include/default_optimizer_switch.inc
 --source include/have_sequence.inc
 --source include/have_innodb.inc
+--source include/have_sequence.inc
 #
 # TODO:
 # Add queries with:
@@ -1859,6 +1860,30 @@ from t1;
 
 drop table t1,t2,t3;
 
+--echo # 
+--echo # MDEV-31380: Assertion `s->table->opt_range_condition_rows <= s->found_records' failed
+--echo #  (assertion in 10.6+, DBL_MAX costs in 10.5)
+--echo # 
+
+CREATE TABLE t1 (a INT, b INT, PRIMARY KEY(a), KEY(b)) ENGINE=InnoDB;
+INSERT INTO t1 SELECT seq, seq FROM seq_1_to_100;
+
+SET
+  @tmp=@@optimizer_use_condition_selectivity,
+  optimizer_use_condition_selectivity = 1,
+  @tmp2=@@optimizer_trace,
+  optimizer_trace=1;
+
+SELECT DISTINCT * FROM t1 WHERE a IN (1, 2);
+
+select 
+  CAST(json_value(json_extract(trace, '$**.chosen_access_method.cost'), '$[0]')
+       as DOUBLE) < 1.0e100
+from information_schema.optimizer_trace;
+
+set optimizer_use_condition_selectivity = @tmp, optimizer_trace=@tmp2;
+drop table t1;
+
 --echo #
 --echo # End of 10.5 tests
 --echo #

mysql-test/suite/gcol/r/gcol_purge.result

@@ -16,7 +16,7 @@ INSERT INTO t1 (f1, f2) VALUES(1,2);
 set global debug_dbug="+d,ib_purge_virtual_index_callback";
 connection con1;
 COMMIT;
-InnoDB		0 transactions not purged
+SET GLOBAL innodb_max_purge_lag_wait=1;
 connection con2;
 commit;
 disconnect con1;

mysql-test/suite/gcol/r/innodb_virtual_debug_purge.result

@@ -78,7 +78,7 @@ SET DEBUG_SYNC= 'now WAIT_FOR uncommitted';
 # enable purge
 COMMIT;
 # wait for purge to process the deleted records.
-InnoDB		0 transactions not purged
+InnoDB		1 transactions not purged
 SET DEBUG_SYNC= 'now SIGNAL purged';
 connection default;
 /* connection default */ ALTER TABLE t1 ADD COLUMN c INT GENERATED ALWAYS AS(a+b), ADD INDEX idx (c), ALGORITHM=INPLACE, LOCK=SHARED;

mysql-test/suite/gcol/t/gcol_purge.test

@@ -23,7 +23,7 @@ set global debug_dbug="+d,ib_purge_virtual_index_callback";
 connection con1;
 COMMIT;
 
---source ../innodb/include/wait_all_purged.inc
+SET GLOBAL innodb_max_purge_lag_wait=1;
 
 connection con2;
 commit;

mysql-test/suite/gcol/t/innodb_virtual_debug_purge.test

@@ -113,7 +113,9 @@ SET DEBUG_SYNC= 'now WAIT_FOR uncommitted';
 COMMIT;
 
 --echo # wait for purge to process the deleted records.
+let $wait_all_purged = 1;
 --source ../../innodb/include/wait_all_purged.inc
+let $wait_all_purged = 0;
 
 SET DEBUG_SYNC= 'now SIGNAL purged';
 

mysql-test/suite/innodb/r/cursor-restore-locking.result

@@ -1,31 +1,34 @@
 SET @save_freq=@@GLOBAL.innodb_purge_rseg_truncate_frequency;
 SET GLOBAL innodb_purge_rseg_truncate_frequency=1;
-CREATE TABLE t (a int PRIMARY KEY, b int NOT NULL UNIQUE) engine = InnoDB;
+CREATE TABLE t (a int PRIMARY KEY, b int NOT NULL UNIQUE) engine = InnoDB, STATS_PERSISTENT=0;
 InnoDB		0 transactions not purged
 connect prevent_purge,localhost,root,,;
 start transaction with consistent snapshot;
 connect con_del_1,localhost,root,,;
 INSERT INTO t VALUES (20,20);
 SET DEBUG_SYNC = 'innodb_row_search_for_mysql_exit SIGNAL first_del_row_search_mvcc_finished WAIT_FOR first_del_cont';
-DELETE FROM t WHERE b = 20;
+DELETE FROM t WHERE b = 20 # trx_1;
 connect con_ins_1,localhost,root,,;
 SET DEBUG_SYNC = 'now WAIT_FOR first_del_row_search_mvcc_finished';
 SET DEBUG_SYNC = 'lock_wait_start SIGNAL first_ins_locked';
 SET DEBUG_SYNC = 'ib_after_row_insert SIGNAL first_ins_row_inserted WAIT_FOR first_ins_cont';
-INSERT INTO t VALUES(10, 20);
+INSERT INTO t VALUES(10, 20) # trx_2;
 connect con_del_2,localhost,root,,;
 SET TRANSACTION ISOLATION LEVEL READ COMMITTED;
 SET DEBUG_SYNC = 'now WAIT_FOR first_ins_locked';
 SET DEBUG_SYNC = 'lock_wait_start SIGNAL second_del_locked';
-DELETE FROM t WHERE b = 20;
+DELETE FROM t WHERE b = 20 # trx_3;
 connection default;
 SET DEBUG_SYNC = 'now WAIT_FOR second_del_locked';
+SET @saved_dbug = @@GLOBAL.debug_dbug;
+SET @@GLOBAL.debug_dbug="d,enable_row_purge_del_mark_exit_sync_point";
 SET DEBUG_SYNC = 'now SIGNAL first_del_cont';
 SET DEBUG_SYNC = 'now WAIT_FOR first_ins_row_inserted';
 connection con_del_1;
 connection default;
 disconnect prevent_purge;
-InnoDB		0 transactions not purged
+SET DEBUG_SYNC = 'now WAIT_FOR row_purge_del_mark_finished';
+SET @@GLOBAL.debug_dbug = @saved_dbug;
 SET DEBUG_SYNC = 'now SIGNAL first_ins_cont';
 connection con_del_2;
 connection con_ins_1;

mysql-test/suite/innodb/r/dml_purge.result

@@ -19,7 +19,7 @@ BEGIN;
 UPDATE t1 SET b=4 WHERE a=3;
 disconnect prevent_purge;
 connection default;
-InnoDB		0 transactions not purged
+SET GLOBAL innodb_max_purge_lag_wait=1;
 connection con1;
 ROLLBACK;
 disconnect con1;

mysql-test/suite/innodb/r/instant_alter_debug.result

@@ -390,11 +390,12 @@ connection stop_purge;
 COMMIT;
 disconnect stop_purge;
 connection default;
-InnoDB		0 transactions not purged
+InnoDB		1 transactions not purged
 SET DEBUG_SYNC='now SIGNAL s2';
 connection dml;
 disconnect dml;
 connection default;
+InnoDB		0 transactions not purged
 SET DEBUG_SYNC=RESET;
 DROP TABLE t1;
 # End of 10.3 tests

mysql-test/suite/innodb/r/instant_alter_purge.result

@@ -1,5 +1,6 @@
 SET @saved_frequency = @@GLOBAL.innodb_purge_rseg_truncate_frequency;
 SET GLOBAL innodb_purge_rseg_truncate_frequency=1;
+InnoDB		0 transactions not purged
 #
 # MDEV-17793 Crash in purge after instant DROP and emptying the table
 #
@@ -16,7 +17,7 @@ COMMIT;
 START TRANSACTION WITH CONSISTENT SNAPSHOT;
 connection default;
 ALTER TABLE t1 ADD COLUMN extra TINYINT UNSIGNED NOT NULL DEFAULT 42;
-InnoDB		1 transactions not purged
+SET GLOBAL innodb_max_purge_lag_wait=1;
 ALTER TABLE t1 DROP extra;
 disconnect prevent_purge;
 InnoDB		0 transactions not purged

mysql-test/suite/innodb/t/cursor-restore-locking.test

@@ -5,7 +5,7 @@ source include/have_debug_sync.inc;
 
 SET @save_freq=@@GLOBAL.innodb_purge_rseg_truncate_frequency;
 SET GLOBAL innodb_purge_rseg_truncate_frequency=1;
-CREATE TABLE t (a int PRIMARY KEY, b int NOT NULL UNIQUE) engine = InnoDB;
+CREATE TABLE t (a int PRIMARY KEY, b int NOT NULL UNIQUE) engine = InnoDB, STATS_PERSISTENT=0;
 
 --source include/wait_all_purged.inc
 --connect(prevent_purge,localhost,root,,)
@@ -14,20 +14,20 @@ start transaction with consistent snapshot;
 --connect(con_del_1,localhost,root,,)
 INSERT INTO t VALUES (20,20);
 SET DEBUG_SYNC = 'innodb_row_search_for_mysql_exit SIGNAL first_del_row_search_mvcc_finished WAIT_FOR first_del_cont';
---send DELETE FROM t WHERE b = 20
+--send DELETE FROM t WHERE b = 20 # trx_1
 
 --connect(con_ins_1,localhost,root,,)
 SET DEBUG_SYNC = 'now WAIT_FOR first_del_row_search_mvcc_finished';
 # It's supposed the following INSERT will be suspended just after
 # lock_wait_start syncpoint, and will be awaken
-# after the previous DELETE commits. ib_after_row_insert will be executed
+# after trx_1 DELETE commits. ib_after_row_insert will be executed
-# after the INSERT is woken up. The previous DELETE will wait for
+# after the trx_2 INSERT is woken up. The trx_1 DELETE will wait for
 # first_del_cont signal before commit, and this signal will be sent later.
 # So it's safe to use two signals in a row here, it's guaranted the first
 # signal will be received before the second signal is sent.
 SET DEBUG_SYNC = 'lock_wait_start SIGNAL first_ins_locked';
 SET DEBUG_SYNC = 'ib_after_row_insert SIGNAL first_ins_row_inserted WAIT_FOR first_ins_cont';
---send INSERT INTO t VALUES(10, 20)
+--send INSERT INTO t VALUES(10, 20) # trx_2
 
 --connect(con_del_2,localhost,root,,)
 # After MDEV-30225 is fixed, the following DELETE creates next-key lock for
@@ -36,24 +36,26 @@ SET DEBUG_SYNC = 'ib_after_row_insert SIGNAL first_ins_row_inserted WAIT_FOR fir
 SET TRANSACTION ISOLATION LEVEL READ COMMITTED;
 SET DEBUG_SYNC = 'now WAIT_FOR first_ins_locked';
 SET DEBUG_SYNC = 'lock_wait_start SIGNAL second_del_locked';
-###############################################################################
+##############################################################################
-# This DELETE is locked by the previous DELETE, after that DELETE is
+# trx_3 DELETE is locked by trx_1 DELETE, after trx_1 DELETE is
-# committed, it will still be locked by the next INSERT on delete-marked
+# committed, it will still be locked by trx_2 INSERT on delete-marked
-# heap_no 2 record. After that INSERT inserted the record with heap_no 3,
+# heap_no 2 record. After trx_2 INSERT inserted the record with heap_no 3,
-# and after heap_no 2 record is purged, this DELETE will be unlocked and
+# and after heap_no 2 record is purged, trx_3 DELETE will be unlocked and
 # must restore persistent cursor position at heap_no 3 record, as it has the
 # same secondary key value as former heap_no 2 record. Then it must be blocked
-# by the previous INSERT, and after the INSERT is committed, it must
+# by trx_2 INSERT, and after trx_2 INSERT is committed, it must
-# delete the record, inserted by the previous INSERT, and the last INSERT(see
+# delete the record, inserted by trx_2 INSERT, and trx_4 INSERT(see
 # below) must be finished without error. But instead this DELETE restores
 # persistent cursor position to supremum, as a result, it does not delete the
-# record, inserted by the previous INSERT, and the last INSERT is finished with
+# record, inserted by trx_2 INSERT, and trx_4 INSERT is finished with
 # duplicate key check error.
 ###############################################################################
---send DELETE FROM t WHERE b = 20
+--send DELETE FROM t WHERE b = 20 # trx_3
 
 --connection default
 SET DEBUG_SYNC = 'now WAIT_FOR second_del_locked';
+SET @saved_dbug = @@GLOBAL.debug_dbug;
+SET @@GLOBAL.debug_dbug="d,enable_row_purge_del_mark_exit_sync_point";
 SET DEBUG_SYNC = 'now SIGNAL first_del_cont';
 SET DEBUG_SYNC = 'now WAIT_FOR first_ins_row_inserted';
 --connection con_del_1
@@ -61,7 +63,8 @@ SET DEBUG_SYNC = 'now WAIT_FOR first_ins_row_inserted';
 
 --connection default
 --disconnect prevent_purge
---source include/wait_all_purged.inc
+SET DEBUG_SYNC = 'now WAIT_FOR row_purge_del_mark_finished';
+SET @@GLOBAL.debug_dbug = @saved_dbug;
 SET DEBUG_SYNC = 'now SIGNAL first_ins_cont';
 
 --connection con_del_2
@@ -74,7 +77,7 @@ SET DEBUG_SYNC = 'now SIGNAL first_ins_cont';
 ###############################################################################
 # Duplicate key error is expected if the bug is not fixed.
 ###############################################################################
-INSERT INTO t VALUES(30, 20);
+INSERT INTO t VALUES(30, 20); # trx_4
 
 --disconnect con_ins_1
 --disconnect con_del_1

mysql-test/suite/innodb/t/dml_purge.test

@@ -32,7 +32,7 @@ UPDATE t1 SET b=4 WHERE a=3;
 
 --connection default
 # Initiate a full purge, which should reset the DB_TRX_ID except for a=3.
---source include/wait_all_purged.inc
+SET GLOBAL innodb_max_purge_lag_wait=1;
 # Initiate a ROLLBACK of the update, which should reset the DB_TRX_ID for a=3.
 --connection con1
 ROLLBACK;

mysql-test/suite/innodb/t/instant_alter_debug.test

@@ -450,7 +450,9 @@ COMMIT;
 disconnect stop_purge;
 
 connection default;
+let $wait_all_purged = 1;
 --source include/wait_all_purged.inc
+let $wait_all_purged = 0;
 SET DEBUG_SYNC='now SIGNAL s2';
 
 connection dml;
@@ -458,6 +460,7 @@ reap;
 disconnect dml;
 
 connection default;
+--source include/wait_all_purged.inc
 SET DEBUG_SYNC=RESET;
 DROP TABLE t1;
 

mysql-test/suite/innodb/t/instant_alter_purge.test

@@ -6,6 +6,7 @@ if ($have_debug) {
 
 SET @saved_frequency = @@GLOBAL.innodb_purge_rseg_truncate_frequency;
 SET GLOBAL innodb_purge_rseg_truncate_frequency=1;
+--source include/wait_all_purged.inc
 
 --echo #
 --echo # MDEV-17793 Crash in purge after instant DROP and emptying the table
@@ -27,8 +28,7 @@ START TRANSACTION WITH CONSISTENT SNAPSHOT;
 connection default;
 
 ALTER TABLE t1 ADD COLUMN extra TINYINT UNSIGNED NOT NULL DEFAULT 42;
-let $wait_all_purged= 1;
+SET GLOBAL innodb_max_purge_lag_wait=1;
---source include/wait_all_purged.inc
 ALTER TABLE t1 DROP extra;
 disconnect prevent_purge;
 let $wait_all_purged= 0;

mysql-test/suite/innodb/t/purge_secondary.test

@@ -1,6 +1,10 @@
 --source include/have_innodb.inc
 --source include/have_sequence.inc
 
+--disable_query_log
+call mtr.add_suppression("InnoDB: Difficult to find free blocks in the buffer pool");
+--enable_query_log
+
 # Ensure that the history list length will actually be decremented by purge.
 SET @saved_frequency = @@GLOBAL.innodb_purge_rseg_truncate_frequency;
 SET GLOBAL innodb_purge_rseg_truncate_frequency = 1;

sql/opt_range.cc

@@ -3030,8 +3030,8 @@ int SQL_SELECT::test_quick_select(THD *thd, key_map keys_to_use,
         restore_nonrange_trees(&param, tree, backup_keys);
       if ((group_trp= get_best_group_min_max(&param, tree, read_time)))
       {
-        param.table->opt_range_condition_rows= MY_MIN(group_trp->records,
+        set_if_smaller(param.table->opt_range_condition_rows,
-                                                  head->stat_records());
+                       group_trp->records);
         Json_writer_object grp_summary(thd, "best_group_range_summary");
 
         if (unlikely(thd->trace_started()))

storage/innobase/handler/ha_innodb.cc

@@ -19422,10 +19422,17 @@ static MYSQL_SYSVAR_ULONG(purge_rseg_truncate_frequency,
   " purge rollback segment(s) on every Nth iteration of purge invocation",
   NULL, NULL, 128, 1, 128, 0);
 
+static void innodb_undo_log_truncate_update(THD *thd, struct st_mysql_sys_var*,
+                                            void*, const void *save)
+{
+  if ((srv_undo_log_truncate= *static_cast<const my_bool*>(save)))
+    srv_wake_purge_thread_if_not_active();
+}
+
 static MYSQL_SYSVAR_BOOL(undo_log_truncate, srv_undo_log_truncate,
   PLUGIN_VAR_OPCMDARG,
   "Enable or Disable Truncate of UNDO tablespace.",
-  NULL, NULL, FALSE);
+  NULL, innodb_undo_log_truncate_update, FALSE);
 
 static MYSQL_SYSVAR_LONG(autoinc_lock_mode, innobase_autoinc_lock_mode,
   PLUGIN_VAR_RQCMDARG | PLUGIN_VAR_READONLY,

storage/innobase/include/trx0purge.h

@@ -39,13 +39,20 @@ Remove the undo log segment from the rseg slot if it is too big for reuse.
 @param[in,out]	mtr		mini-transaction */
 void
 trx_purge_add_undo_to_history(const trx_t* trx, trx_undo_t*& undo, mtr_t* mtr);
+
+/**
+Remove unnecessary history data from rollback segments. NOTE that when this
+function is called, the caller (purge_coordinator_callback)
+must not have any latches on undo log pages!
+*/
+void trx_purge_truncate_history();
+
 /**
 Run a purge batch.
 @param n_tasks       number of purge tasks to submit to the queue
 @param history_size  trx_sys.history_size()
-@param truncate      whether to truncate the history at the end of the batch
 @return number of undo log pages handled in the batch */
-ulint trx_purge(ulint n_tasks, ulint history_size, bool truncate);
+ulint trx_purge(ulint n_tasks, ulint history_size);
 
 /** Rollback segements from a given transaction with trx-no
 scheduled for purge. */
@@ -285,6 +292,18 @@ public:
     typically via purge_sys_t::view_guard. */
     return view.low_limit_no();
   }
+  /** A wrapper around ReadView::sees(). */
+  trx_id_t sees(trx_id_t id) const
+  {
+    /* This function may only be called by purge_coordinator_callback().
+
+    The purge coordinator task may call this without holding any latch,
+    because it is the only thread that may modify purge_sys.view.
+
+    Any other threads that access purge_sys.view must hold purge_sys.latch,
+    typically via purge_sys_t::view_guard. */
+    return view.sees(id);
+  }
   /** A wrapper around trx_sys_t::clone_oldest_view(). */
   template<bool also_end_view= false>
   void clone_oldest_view()

storage/innobase/row/row0purge.cc

@@ -47,6 +47,7 @@ Created 3/14/1997 Heikki Tuuri
 #include "handler.h"
 #include "ha_innodb.h"
 #include "fil0fil.h"
+#include "debug_sync.h"
 #include <mysql/service_thd_mdl.h>
 
 /*************************************************************************
@@ -631,7 +632,17 @@ row_purge_del_mark(
     mem_heap_free(heap);
   }
 
-  return row_purge_remove_clust_if_poss(node);
+  bool result= row_purge_remove_clust_if_poss(node);
+
+#ifdef ENABLED_DEBUG_SYNC
+  DBUG_EXECUTE_IF("enable_row_purge_del_mark_exit_sync_point",
+                  debug_sync_set_action
+                  (current_thd,
+                   STRING_WITH_LEN("now SIGNAL row_purge_del_mark_finished"));
+                  );
+#endif
+
+  return result;
 }
 
 void purge_sys_t::wait_SYS()
@@ -850,6 +861,9 @@ skip_secondaries:
 				   buf_page_get(page_id_t(rseg.space->id,
 							  page_no),
 						0, RW_X_LATCH, &mtr)) {
+				block->page.set_accessed();
+				buf_page_make_young_if_needed(&block->page);
+
 				byte* data_field = block->page.frame
 					+ offset + internal_offset;
 

storage/innobase/srv/srv0srv.cc

@@ -1296,17 +1296,14 @@ static tpool::waitable_task purge_coordinator_task
 static tpool::timer *purge_coordinator_timer;
 
 /** Wake up the purge threads if there is work to do. */
-void
+void srv_wake_purge_thread_if_not_active()
-srv_wake_purge_thread_if_not_active()
 {
-	ut_ad(!srv_read_only_mode);
+  ut_ad(!srv_read_only_mode);
 
-	if (purge_sys.enabled() && !purge_sys.paused()
+  if (purge_sys.enabled() && !purge_sys.paused() &&
-	    && trx_sys.history_exists()) {
+      (srv_undo_log_truncate || trx_sys.history_exists()) &&
-		if(++purge_state.m_running == 1) {
+      ++purge_state.m_running == 1)
-			srv_thread_pool->submit_task(&purge_coordinator_task);
+    srv_thread_pool->submit_task(&purge_coordinator_task);
-		}
-	}
 }
 
 /** @return whether the purge tasks are active */
@@ -1697,13 +1694,20 @@ fewer_threads:
     m_history_length= history_size;
 
     if (!history_size)
+    {
       srv_dml_needed_delay= 0;
-    else if (trx_purge(n_use_threads, history_size,
+      trx_purge_truncate_history();
-                       !(++count % srv_purge_rseg_truncate_frequency) ||
+    }
-                       purge_sys.truncate.current ||
+    else
-                       (srv_shutdown_state != SRV_SHUTDOWN_NONE &&
+    {
-                        srv_fast_shutdown == 0)))
+      ulint n_pages_handled= trx_purge(n_use_threads, history_size);
-      continue;
+      if (!(++count % srv_purge_rseg_truncate_frequency) ||
+          purge_sys.truncate.current ||
+          (srv_shutdown_state != SRV_SHUTDOWN_NONE && srv_fast_shutdown == 0))
+        trx_purge_truncate_history();
+      if (n_pages_handled)
+        continue;
+    }
 
     if (srv_dml_needed_delay);
     else if (m_running == sigcount)

storage/innobase/trx/trx0purge.cc

@@ -363,7 +363,6 @@ trx_purge_add_undo_to_history(const trx_t* trx, trx_undo_t*& undo, mtr_t* mtr)
                                  TRX_UNDO_NEEDS_PURGE, 1U);
 }
 
-
 /** Free an undo log segment.
 @param block     rollback segment header page
 @param mtr       mini-transaction */
@@ -561,10 +560,11 @@ __attribute__((optimize(0)))
 # endif
 #endif
 /**
-Removes unnecessary history data from rollback segments. NOTE that when this
+Remove unnecessary history data from rollback segments. NOTE that when this
-function is called, the caller must not have any latches on undo log pages!
+function is called, the caller (purge_coordinator_callback)
+must not have any latches on undo log pages!
 */
-TRANSACTIONAL_TARGET static void trx_purge_truncate_history()
+TRANSACTIONAL_TARGET void trx_purge_truncate_history()
 {
   ut_ad(purge_sys.head <= purge_sys.tail);
   purge_sys_t::iterator &head= purge_sys.head.trx_no
@@ -586,7 +586,7 @@ TRANSACTIONAL_TARGET static void trx_purge_truncate_history()
       if (dberr_t e=
           trx_purge_truncate_rseg_history(rseg, head,
                                           !rseg.is_referenced() &&
-                                          rseg.needs_purge <= head.trx_no))
+                                          purge_sys.sees(rseg.needs_purge)))
         err= e;
       rseg.latch.wr_unlock();
     }
@@ -644,7 +644,7 @@ TRANSACTIONAL_TARGET static void trx_purge_truncate_history()
 
       rseg.latch.rd_lock(SRW_LOCK_CALL);
       ut_ad(rseg.skip_allocation());
-      if (rseg.is_referenced() || rseg.needs_purge > head.trx_no)
+      if (rseg.is_referenced() || !purge_sys.sees(rseg.needs_purge))
       {
 not_free:
         rseg.latch.rd_unlock();
@@ -658,7 +658,7 @@ not_free:
       for (const trx_undo_t *undo= UT_LIST_GET_FIRST(rseg.undo_cached); undo;
            undo= UT_LIST_GET_NEXT(undo_list, undo))
       {
-        if (head.trx_no < undo->trx_id)
+        if (head.trx_no && head.trx_no < undo->trx_id)
           goto not_free;
         else
           cached+= undo->size;
@@ -791,7 +791,7 @@ not_free:
         continue;
 
       ut_ad(!rseg.is_referenced());
-      ut_ad(rseg.needs_purge <= head.trx_no);
+      ut_ad(!head.trx_no || rseg.needs_purge <= head.trx_no);
 
       buf_block_t *rblock= trx_rseg_header_create(&space,
                                                   &rseg - trx_sys.rseg_array,
@@ -1264,10 +1264,8 @@ TRANSACTIONAL_INLINE void purge_sys_t::clone_end_view()
 Run a purge batch.
 @param n_tasks       number of purge tasks to submit to the queue
 @param history_size  trx_sys.history_size()
-@param truncate      whether to truncate the history at the end of the batch
 @return number of undo log pages handled in the batch */
-TRANSACTIONAL_TARGET
+TRANSACTIONAL_TARGET ulint trx_purge(ulint n_tasks, ulint history_size)
-ulint trx_purge(ulint n_tasks, ulint history_size, bool truncate)
 {
 	que_thr_t*	thr = NULL;
 	ulint		n_pages_handled;
@@ -1319,10 +1317,6 @@ ulint trx_purge(ulint n_tasks, ulint history_size, bool truncate)
 
 	purge_sys.clone_end_view();
 
-	if (truncate) {
-		trx_purge_truncate_history();
-	}
-
 	MONITOR_INC_VALUE(MONITOR_PURGE_INVOKED, 1);
 	MONITOR_INC_VALUE(MONITOR_PURGE_N_PAGE_HANDLED, n_pages_handled);