Adds a helper for transactions with a specific isolation level

[ls4f]

Now that Korma has moved to the new JDBC, I figure it should have a way of specifying the desired isolation level (without ConnectionCustomizerClassName which I had suggested in a previous pull request).

[immoh]

While I think the functionality would be useful to have, I’m not really comfortable with introducing new macro for it. From API perspective it would be best to give isolation level and read-only flag as options to transaction macro.

[ls4f]

I couldn't think of a nice way to alter the transaction macro and preserve behavior at the same time. If you have an idea, I'm willing to rework it.

[immoh]

API could look like this:

(transaction {:isolation-level :serializable :read-ony? false}
  (insert ..)
  (delete ..))

also supporting

(transaction
  (insert ..)
  (delete ..))

[ls4f]

I figured as much. What I meant was that I'm not terribly sure if I can get the macro right. I believe now it's ok, meaning it recognizes the map and it should not break existing code. It does however look uglier to me that way, and I can't think of a better way to do it at the moment. I think the read-only? flag was pushed in clojure-jdbc 0.3.5 so I bumped the version.

If you think it's ok, I'll squash the commits.

[immoh]

Looks good. Some things I would still like to see:

• if body is just one map we shouldn't treat is at options.
• :arglists metadata to indicate different usages: [options & body] and [& body]
• pure-body could be just body
• tests covering option usage

[ls4f]

Ok

• Fixed, now options are parsed only if body is not a single element
• Added
• Changed, though I prefer not to shadow params that way
• Added a test for the isolation level. ReadOnly appears to be something which not every database does at the transaction level (H2/SQLite do it at connection level, MySQL might not have transactions at all) so it seemed safer not to check it. Plus, I'm not sure what else is there in the test environment.

[immoh]

I think the test is ok. Please squash commits and rebase on latest master, I'll merge it then.

[ls4f]

Done

[immoh]

Thanks!