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Add locks for sequence's to ensure that there is only one writer or many readers

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This is needed for MyISAM and other storage engines which normally
relies on THR_LOCK's to ensure that one is not writing the same block
one could be reading from.
This commit is contained in:
Monty
2017-05-29 16:08:11 +03:00
parent d7e3120da8
commit 7e5bd1500f
6 changed files with 97 additions and 48 deletions
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30
sql/ha_sequence.h
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@ -60,6 +60,9 @@ private:
SEQUENCE *sequence; /* From table_share->sequence */
public:
/* Set when handler is write locked */
bool write_locked;
ha_sequence(handlerton *hton, TABLE_SHARE *share);
~ha_sequence();
@ -89,16 +92,36 @@ public:
/* For ALTER ONLINE TABLE */
bool check_if_incompatible_data(HA_CREATE_INFO *create_info,
uint table_changes);
void write_lock() { write_locked= 1;}
void unlock() { write_locked= 0; }
bool is_locked() { return write_locked; }
/* Functions that are directly mapped to the underlying handler */
int rnd_init(bool scan)
{ return file->rnd_init(scan); }
/*
We need to have a lock here to protect engines like MyISAM from
simultaneous read and write. For sequence's this is not critical
as this function is used extremely seldom.
*/
int rnd_next(uchar *buf)
{ return file->rnd_next(buf); }
{
int error;
table->s->sequence->read_lock(table);
error= file->rnd_next(buf);
table->s->sequence->read_unlock(table);
return error;
}
int rnd_end()
{ return file->rnd_end(); }
int rnd_pos(uchar *buf, uchar *pos)
{ return file->rnd_pos(buf, pos); }
{
int error;
table->s->sequence->read_lock(table);
error= file->rnd_pos(buf, pos);
table->s->sequence->read_unlock(table);
return error;
}
void position(const uchar *record)
{ return file->position(record); }
const char *table_type() const
@ -136,8 +159,5 @@ public:
file= file_arg;
init(); /* Update cached_table_flags */
}
/* To inform handler that sequence is already locked by called */
bool sequence_locked;
};
#endif