mariadb/storage/innobase/include/row0purge.h
Thirunarayanan Balathandayuthapani 8b0d4cff07 MDEV-15855 Deadlock between purge thread and DDL statement
Problem:
========
Truncate operation holds MDL on the table (t1) and tries to
acquire InnoDB dict_operation_lock. Purge holds dict_operation_lock
and tries to acquire MDL on the table (t1) to evaluate virtual
column expressions for indexed virtual columns.
It leads to deadlock of purge and truncate table (DDL).

Solution:
=========
If purge tries to acquire MDL on the table then it should do the following:

i) Purge should release all innodb latches (including dict_operation_lock)
before acquiring metadata lock on the table.

ii) After acquiring metadata lock on the table, it should check whether the
table was dropped or renamed. If the table is dropped then purge should
ignore the undo log record. If the table is renamed then it should
release the old MDL and acquire MDL on the new name.

iii) Once purge acquires MDL, it should use the SQL table handle for all
the remaining virtual index for the purge record.

purge_node_t: Introduce new virtual column information to know whether
the MDL was acquired successfully.

This is joint work with Marko Mäkelä.
2018-07-06 17:13:53 +03:00

154 lines
5.4 KiB
C

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/**************************************************//**
@file include/row0purge.h
Purge obsolete records
Created 3/14/1997 Heikki Tuuri
*******************************************************/
#ifndef row0purge_h
#define row0purge_h
#include "univ.i"
#include "data0data.h"
#include "btr0types.h"
#include "btr0pcur.h"
#include "dict0types.h"
#include "trx0types.h"
#include "que0types.h"
#include "row0types.h"
#include "ut0vec.h"
#include "row0mysql.h"
/** Create a purge node to a query graph.
@param[in] parent parent node, i.e., a thr node
@param[in] heap memory heap where created
@return own: purge node */
purge_node_t*
row_purge_node_create(
que_thr_t* parent,
mem_heap_t* heap)
MY_ATTRIBUTE((warn_unused_result));
/** Determines if it is possible to remove a secondary index entry.
Removal is possible if the secondary index entry does not refer to any
not delete marked version of a clustered index record where DB_TRX_ID
is newer than the purge view.
NOTE: This function should only be called by the purge thread, only
while holding a latch on the leaf page of the secondary index entry
(or keeping the buffer pool watch on the page). It is possible that
this function first returns true and then false, if a user transaction
inserts a record that the secondary index entry would refer to.
However, in that case, the user transaction would also re-insert the
secondary index entry after purge has removed it and released the leaf
page latch.
@param[in,out] node row purge node
@param[in] index secondary index
@param[in] entry secondary index entry
@param[in,out] sec_pcur secondary index cursor or NULL
if it is called for purge buffering
operation.
@param[in,out] sec_mtr mini-transaction which holds
secondary index entry or NULL if it is
called for purge buffering operation.
@param[in] is_tree true=pessimistic purge,
false=optimistic (leaf-page only)
@return true if the secondary index record can be purged */
bool
row_purge_poss_sec(
purge_node_t* node,
dict_index_t* index,
const dtuple_t* entry,
btr_pcur_t* sec_pcur=NULL,
mtr_t* sec_mtr=NULL,
bool is_tree=false);
/***************************************************************
Does the purge operation for a single undo log record. This is a high-level
function used in an SQL execution graph.
@return query thread to run next or NULL */
que_thr_t*
row_purge_step(
/*===========*/
que_thr_t* thr) /*!< in: query thread */
MY_ATTRIBUTE((nonnull, warn_unused_result));
/* Purge node structure */
struct purge_node_t{
que_common_t common; /*!< node type: QUE_NODE_PURGE */
/*----------------------*/
/* Local storage for this graph node */
roll_ptr_t roll_ptr;/* roll pointer to undo log record */
ib_vector_t* undo_recs;/*!< Undo recs to purge */
undo_no_t undo_no;/*!< undo number of the record */
ulint rec_type;/*!< undo log record type: TRX_UNDO_INSERT_REC,
... */
dict_table_t* table; /*!< table where purge is done */
ulint cmpl_info;/* compiler analysis info of an update */
upd_t* update; /*!< update vector for a clustered index
record */
dtuple_t* ref; /*!< NULL, or row reference to the next row to
handle */
dtuple_t* row; /*!< NULL, or a copy (also fields copied to
heap) of the indexed fields of the row to
handle */
dict_index_t* index; /*!< NULL, or the next index whose record should
be handled */
mem_heap_t* heap; /*!< memory heap used as auxiliary storage for
row; this must be emptied after a successful
purge of a row */
ibool found_clust;/* TRUE if the clustered index record
determined by ref was found in the clustered
index, and we were able to position pcur on
it */
btr_pcur_t pcur; /*!< persistent cursor used in searching the
clustered index record */
ibool done; /* Debug flag */
trx_id_t trx_id; /*!< trx id for this purging record */
/** Virtual column information about opening of MariaDB table.
It resets after processing each undo log record. */
purge_vcol_info_t vcol_info;
#ifdef UNIV_DEBUG
/***********************************************************//**
Validate the persisent cursor. The purge node has two references
to the clustered index record - one via the ref member, and the
other via the persistent cursor. These two references must match
each other if the found_clust flag is set.
@return true if the persistent cursor is consistent with
the ref member.*/
bool validate_pcur();
#endif
/** Whether purge failed to open the maria table for virtual column
computation.
@return true if the table failed to open. */
bool vcol_op_failed() const { return !vcol_info.validate(); }
};
#endif