Can you help set me straight?
I recently upgraded from coldfusion 5 to coldfusion mx 7. In the process
I also switched from odbc to jdbc connections to mysql
(4.0.21-nt-max-log).
>From looking at the query log, I'm now getting...
SHOW VARIABLES
...once per connection
followed by...
SET SESSION TRANSACTION ISOLATION LEVEL READ COMMITTED
-> followed by one or more...
^ SELECT
^
^ followed by...
^ SET autocommit=1
^ SET SESSION TRANSACTION ISOLATION LEVEL READ COMMITTED
^
<- this pattern repeats until the final Quit for the connection.
I can include actual entries from the query log if you would like to see
them.
Is SET SESSION TRANSACTION ISOLATION LEVEL READ COMMITTED applicable to
MyISAM tables? I am not using transactions and InnoDB or BDB tables.
Since I am not using transactions is this statement irrelevant (and
unneeded)?
I'm also a little surprised by the SET autocommit=1. The manual says...
The other non-transactional storage engines in MySQL Server (such as
MyISAM) follow a different paradigm for data integrity called ``atomic
operations.'' In transactional terms, MyISAM tables effectively always
operate in AUTOCOMMIT=1 mode. Atomic operations often offer comparable
integrity with higher performance.
and...
By default, MySQL runs with autocommit mode enabled. This means that as
soon as you execute a statement that updates (modifies) a table, MySQL
stores the update on disk.
and...
Note that if you are not using transaction-safe tables, any changes are
stored at once, regardless of the status of autocommit mode.
So it would seem that the SET autocommit=1 commands being seen in the
query log are not needed. I checked and autocommit is enabled (not that
it would seem to matter since I'm using MyISAM tables)...
mysql> SELECT @@AUTOCOMMIT;
+--------------+
| @@autocommit |
+--------------+
| 1 |
+--------------+
Am I right that neither
SET SESSION TRANSACTION ISOLATION LEVEL READ COMMITTED
SET autocommit=1
are appropriate/needed for MyISAM tables?
If that is true, then I guess my next step is to try and find out why
coldfusion mx 7 is issuing them to MySQL when using MyISAM tables.
Thanks,
Daniel
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