Transaction improvements

[repomaa]

• actually test transaction operations (was using Repo instead of tx inside transaction! block
• streamline CUD methods
• add all read methods to LiveTransaction

I noticed the using Repo.all inside of a transaction! block won't return any of the records created inside of the transaction which is why i included all read methods for LiveTransaction

[fridgerator]

Nice!

[fridgerator]

On this line: https://github.com/jreinert/crecto/blob/transaction_improvements/src/crecto/adapters/mysql_adapter.cr#L58

Does this work?

if conn.is_a?(DB::TopLevelTransaction)
  return execute(conn, "SELECT * FROM #{changeset.instance.class.table_name} WHERE (#{changeset.instance.class.primary_key_field} = #{last_insert_id})")
end

[repomaa]

well, last_insert_id is undefined up there but basically it would be the same as leaving the guard clause out. :/ In this case the method just freezes the program.

[repomaa]

To recap: This PR is on hold, because the specs for the query methods introduced to LiveTransaction rely on having the the inserted record (with it's id set) returned. This is currently not working for MySQL. A guard clause in the insert method of the mysql_adapter prevents the fetching of the inserted record. When it's removed the method will block indefinetely.

[repomaa]

I now use compiler flags to determine which db the specs are run against and depending on those enable/disable some specs. Nested transactions aren't supported by sqlite so i exclude the spec for it when run against sqlite. The tx read spec (reading records created within a transaction from within the same transaction) should work for all databases but there are underlying issues in the mysql and sqlite drivers that prevent this. This is why i mark the tx read spec as pending for mysql and sqlite.

[repomaa]

What's a bit of a mystery to me is the currently failing spec for delete_all in a transaction for sqlite. I can't reproduce this on my local machine (arch linux with sqlite 3.30.1). Any help in figuring out what goes wrong there would be much appreciated!