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MDEV-19745 BACKUP STAGE BLOCK_DDL hangs on flush sequence table

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Problem was that FLUSH TABLES where trying to read latest sequence state
which conflicted with a running ALTER SEQUENCE. Removed the reading
of the state, when opening a table for FLUSH, as it's not needed in this
case.

Other thing:
- Fixed a potential issue with concurrently running ALTER SEQUENCE where
  the later ALTER could potentially read old data
This commit is contained in:
Monty
2020-06-08 15:13:04 +03:00
parent 08d475c73b
commit 6a3b581b90
5 changed files with 26 additions and 11 deletions
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4
include/my_base.h
View File

@ -55,6 +55,10 @@
*/
#define HA_OPEN_FOR_ALTER 8192U
/* Open table for FLUSH */
#define HA_OPEN_FOR_FLUSH 8192U
/* The following is parameter to ha_rkey() how to use key */
/*

11
sql/ha_sequence.cc
View File

@ -108,8 +108,12 @@ int ha_sequence::open(const char *name, int mode, uint flags)
MY_TEST(flags & HA_OPEN_INTERNAL_TABLE);
reset_statistics();
/* Don't try to read the initial row the call is part of create code */
if (!(flags & (HA_OPEN_FOR_CREATE | HA_OPEN_FOR_REPAIR)))
/*
Don't try to read the initial row if the call is part of CREATE, REPAIR
or FLUSH
*/
if (!(flags & (HA_OPEN_FOR_CREATE | HA_OPEN_FOR_REPAIR |
HA_OPEN_FOR_FLUSH)))
{
if (unlikely((error= table->s->sequence->read_initial_values(table))))
file->ha_close();
@ -121,7 +125,8 @@ int ha_sequence::open(const char *name, int mode, uint flags)
The following is needed to fix comparison of rows in
ha_update_first_row() for InnoDB
*/
memcpy(table->record[1], table->s->default_values, table->s->reclength);
if (!error)
memcpy(table->record[1], table->s->default_values, table->s->reclength);
}
DBUG_RETURN(error);
}

9
sql/sql_base.cc
View File

@ -598,12 +598,15 @@ bool flush_tables(THD *thd, flush_tables_type flag)
else
{
/*
HA_OPEN_FOR_ALTER is used to allow us to open the table even if
TABLE_SHARE::incompatible_version is set.
HA_OPEN_FOR_FLUSH is used to allow us to open the table even if
TABLE_SHARE::incompatible_version is set. It also will tell
SEQUENCE engine that we don't have to read the sequence information
(which may cause deadlocks with concurrently running ALTER TABLE or
ALTER SEQUENCE) as we will close the table at once.
*/
if (!open_table_from_share(thd, share, &empty_clex_str,
HA_OPEN_KEYFILE, 0,
HA_OPEN_FOR_ALTER,
HA_OPEN_FOR_ALTER | HA_OPEN_FOR_FLUSH,
tmp_table, FALSE,
NULL))
{

10
sql/sql_sequence.cc
View File

@ -453,7 +453,7 @@ int SEQUENCE::read_initial_values(TABLE *table)
/*
There is already a mdl_ticket for this table. However, for list_fields
the MDL lock is of type MDL_SHARED_HIGH_PRIO which is not usable
for doing a able lock. Get a proper read lock to solve this.
for doing a table lock. Get a proper read lock to solve this.
*/
if (table->mdl_ticket == 0)
{
@ -929,6 +929,8 @@ bool Sql_cmd_alter_sequence::execute(THD *thd)
table= first_table->table;
seq= table->s->sequence;
seq->write_lock(table);
new_seq->reserved_until= seq->reserved_until;
/* Copy from old sequence those fields that the user didn't specified */
@ -961,18 +963,18 @@ bool Sql_cmd_alter_sequence::execute(THD *thd)
first_table->db.str,
first_table->table_name.str);
error= 1;
seq->write_unlock(table);
goto end;
}
table->s->sequence->write_lock(table);
if (likely(!(error= new_seq->write(table, 1))))
{
/* Store the sequence values in table share */
table->s->sequence->copy(new_seq);
seq->copy(new_seq);
}
else
table->file->print_error(error, MYF(0));
table->s->sequence->write_unlock(table);
seq->write_unlock(table);
if (trans_commit_stmt(thd))
error= 1;
if (trans_commit_implicit(thd))

3
sql/table.cc
View File

@ -3891,7 +3891,8 @@ enum open_frm_error open_table_from_share(THD *thd, TABLE_SHARE *share,
outparam->write_row_record= NULL;
if (share->incompatible_version &&
!(ha_open_flags & (HA_OPEN_FOR_ALTER | HA_OPEN_FOR_REPAIR)))
!(ha_open_flags & (HA_OPEN_FOR_ALTER | HA_OPEN_FOR_REPAIR |
HA_OPEN_FOR_FLUSH)))
{
/* one needs to run mysql_upgrade on the table */
error= OPEN_FRM_NEEDS_REBUILD;