diff options
| author | unknown <heikki@hundin.mysql.fi> | 2004-02-08 12:53:31 +0200 |
|---|---|---|
| committer | unknown <heikki@hundin.mysql.fi> | 2004-02-08 12:53:31 +0200 |
| commit | b0076aad731e2e2ea12c5261e0b89c27c5e34f2f (patch) | |
| tree | 6e3837457d2aa459de0f45d419f33f1f0ae85a8c /sql/ha_innodb.cc | |
| parent | 496cbfe8a9b65e2f77530fff849b98368d6cc47b (diff) | |
| download | mariadb-git-b0076aad731e2e2ea12c5261e0b89c27c5e34f2f.tar.gz | |
ha_innodb.cc:
If AUTOCOMMIT=1, then we do not need to make a plain SELECT set shared locks even on the SERIALIZABLE isolation level, because we know the transaction is read-only: a read-only transaction can always be performed on the REPEATABLE READ level, and that does not endanger the serializability
sql/ha_innodb.cc:
If AUTOCOMMIT=1, then we do not need to make a plain SELECT set shared locks even on the SERIALIZABLE isolation level, because we know the transaction is read-only: a read-only transaction can always be performed on the REPEATABLE READ level, and that does not endanger the serializability
Diffstat (limited to 'sql/ha_innodb.cc')
| -rw-r--r-- | sql/ha_innodb.cc | 14 |
1 files changed, 10 insertions, 4 deletions
diff --git a/sql/ha_innodb.cc b/sql/ha_innodb.cc index 68052014f57..01af07f34ec 100644 --- a/sql/ha_innodb.cc +++ b/sql/ha_innodb.cc @@ -539,7 +539,7 @@ innobase_query_caching_of_table_permitted( if (thd->variables.tx_isolation == ISO_SERIALIZABLE) { /* In the SERIALIZABLE mode we add LOCK IN SHARE MODE to every - plain SELECT */ + plain SELECT if AUTOCOMMIT is not on. */ return((my_bool)FALSE); } @@ -4483,11 +4483,17 @@ ha_innobase::external_lock( } if (trx->isolation_level == TRX_ISO_SERIALIZABLE - && prebuilt->select_lock_type == LOCK_NONE) { + && prebuilt->select_lock_type == LOCK_NONE + && (thd->options + & (OPTION_NOT_AUTOCOMMIT | OPTION_BEGIN))) { - /* To get serializable execution we let InnoDB + /* To get serializable execution, we let InnoDB conceptually add 'LOCK IN SHARE MODE' to all SELECTs - which otherwise would have been consistent reads */ + which otherwise would have been consistent reads. An + exception is consistent reads in the AUTOCOMMIT=1 mode: + we know that they are read-only transactions, and they + can be serialized also if performed as consistent + reads. */ prebuilt->select_lock_type = LOCK_S; } |