MDEV-12219 Discard temporary undo logs at transaction commit

Starting with MySQL 5.7, temporary tables in InnoDB are handled
differently from persistent tables. Because temporary tables are
private to a connection, concurrency control and multi-versioning
(MVCC) are not applicable. For performance reasons, purge is
disabled as well. Rollback is supported for temporary tables;
that is why we have the temporary undo logs in the first place.

Because MVCC and purge are disabled for temporary tables, we should
discard all temporary undo logs already at transaction commit,
just like we discard the persistent insert_undo logs. Before this
change, update_undo logs were being preserved.

trx_temp_undo_t: A wrapper for temporary undo logs, comprising
a rollback segment and a single temporary undo log.

trx_rsegs_t::m_noredo: Use trx_temp_undo_t.
(Instead of insert_undo, update_undo, there will be a single undo.)

trx_is_noredo_rseg_updated(), trx_is_rseg_assigned(): Remove.

trx_undo_add_page(): Remove the parameter undo_ptr.
Acquire and release the rollback segment mutex inside the function.

trx_undo_free_last_page(): Remove the parameter trx.

trx_undo_truncate_end(): Remove the parameter trx, and add the
parameter is_temp. Clean up the code a bit.

trx_undo_assign_undo(): Split the parameter undo_ptr into rseg, undo.

trx_undo_commit_cleanup(): Renamed from trx_undo_insert_cleanup().
Replace the parameter undo_ptr with undo.
This will discard the temporary undo or insert_undo log at
commit/rollback.

trx_purge_add_update_undo_to_history(), trx_undo_update_cleanup():
Remove 3 parameters. Always operate on the persistent update_undo.

trx_serialise(): Renamed from trx_serialisation_number_get().

trx_write_serialisation_history(): Simplify the code flow.
If there are no persistent changes, do not update MONITOR_TRX_COMMIT_UNDO.

trx_commit_in_memory(): Simplify the logic, and add assertions.

trx_undo_page_report_modify(): Keep a direct reference to the
persistent update_undo log.

trx_undo_report_row_operation(): Simplify some code.
Always assign TRX_UNDO_INSERT for temporary undo logs.

trx_prepare_low(): Keep only one parameter. Prepare all 3 undo logs.

trx_roll_try_truncate(): Remove the parameter undo_ptr.
Try to truncate all 3 undo logs of the transaction.

trx_roll_pop_top_rec_of_trx_low(): Remove.

trx_roll_pop_top_rec_of_trx(): Remove the redundant parameter
trx->roll_limit. Clear roll_limit when exhausting the undo logs.
Consider all 3 undo logs at once, prioritizing the persistent
undo logs.

row_undo(): Minor cleanup. Let trx_roll_pop_top_rec_of_trx()
reset the trx->roll_limit.

1 files changed, 10 insertions, 25 deletions

diff --git a/storage/innobase/include/trx0roll.h b/storage/innobase/include/trx0roll.h
index ec4c7d57e5d..1f2e98b9708 100644
--- a/storage/innobase/include/trx0roll.h
+++ b/storage/innobase/include/trx0roll.h
@@ -1,6 +1,7 @@
 /*****************************************************************************
 
 Copyright (c) 1996, 2016, Oracle and/or its affiliates. All Rights Reserved.
+Copyright (c) 2015, 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
@@ -50,32 +51,16 @@ trx_savept_t
 trx_savept_take(
 /*============*/
 	trx_t*	trx);	/*!< in: transaction */
-/********************************************************************//**
-Pops the topmost record when the two undo logs of a transaction are seen
-as a single stack of records ordered by their undo numbers.
-@return undo log record copied to heap, NULL if none left, or if the
-undo number of the top record would be less than the limit */
-trx_undo_rec_t*
-trx_roll_pop_top_rec_of_trx_low(
-/*============================*/
-	trx_t*		trx,		/*!< in/out: transaction */
-	trx_undo_ptr_t*	undo_ptr,	/*!< in: rollback segment to look
-					for next undo log record. */
-	undo_no_t	limit,		/*!< in: least undo number we need */
-	roll_ptr_t*	roll_ptr,	/*!< out: roll pointer to undo record */
-	mem_heap_t*	heap);		/*!< in/out: memory heap where copied */
-
-/********************************************************************//**
-Get next undo log record from redo and noredo rollback segments.
-@return undo log record copied to heap, NULL if none left, or if the
-undo number of the top record would be less than the limit */
+
+/** Get the last undo log record of a transaction (for rollback).
+@param[in,out]	trx		transaction
+@param[out]	roll_ptr	DB_ROLL_PTR to the undo record
+@param[in,out]	heap		memory heap for allocation
+@return	undo log record copied to heap
+@retval	NULL if none left or the roll_limit (savepoint) was reached */
 trx_undo_rec_t*
-trx_roll_pop_top_rec_of_trx(
-/*========================*/
-	trx_t*		trx,		/*!< in: transaction */
-	undo_no_t	limit,		/*!< in: least undo number we need */
-	roll_ptr_t*	roll_ptr,	/*!< out: roll pointer to undo record */
-	mem_heap_t*	heap);		/*!< in: memory heap where copied */
+trx_roll_pop_top_rec_of_trx(trx_t* trx, roll_ptr_t* roll_ptr, mem_heap_t* heap)
+	MY_ATTRIBUTE((nonnull, warn_unused_result));
 
 /*******************************************************************//**
 Rollback or clean up any incomplete transactions which were