locking in a session-less context

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1

Can isolation levels and lockmode be used in a session-less context? IE, can I do something like

http://localhost/tamino/mydb/_xql=…?_isolationLevel=committedCommand

The manual says:
uncommittedDocument - This value is the default value for the _isolationLevel parameter if used in database operations in a session-less context.

Does that imply that you can set isolationLevel to anything, or does it mean that setting isolation level in a session-less context has no meaning?

Bill

2

Hi Bill,

you can set _isolationLevel also with session-less requests. But note, that every command immediately commits or rolls back its transaction and consequently releases all locks.

Regards
Michael

3

Thanks Michael.

OK, we were able to get locking in a session-less context to work here. However, in order to be able to specify an _isolationLevel you need to also specify _lockMode=none. Otherwise, Tamino seems to ignore whatever isolationLevel you specified, and does dirty reads. (This is different than the procedure for a _connect call, where you only need to specify isolationLevel.)

So, it ended up being something like:

_xquery=...&_isolationLevel=committedCommand&_lockmode=none



Any comments? Seems like you should either change this behavior or update the documentation.

Bill

4

Also, can _transactionTimeout be specified in a session-less context?

Basically, the problem is that the X-Machine doc says that _isolationLevel, _transactionTimeout, etc. can only be set when a session is started (on the _connect command), but the Java API doc states that these values can be set/reset at the start of each transaction. In auto-commit (a.k.a. session-less context) mode, each command is in it’s own transaction, and thus the parameters can be set for each command.

Bill

5

Hi Bill,

it is a bug that you can/have to specify _lockMode=none when defining an isolation level for a sessionless request. This will be fixed with next major release (V4.2).

_isolationLevel can be set for every transaction (also sessionless). _lockWait and _lockMode can be set for every request (also sessionless). This will be clarified in the documentation of the next major release.

_transactionTimeout only has an effect when connecting to the database and applies for the entire session. In all other cases it will be ignored.

Regards,

Michael

6

Thank you Michael.

As usual your reply is very helpful. So, transactionTimeout is unique in that in can only be set at connect time.

On a related note, regarding API4J and .NET API, transactionTimeout cannot be set at all; you may want to add this feature. Also, the cursor related options of scroll=yes/no (X-Query and XQuery) and sensitive=vague/no (XQuery only) are also unavailable through the API. I assume you would want to add those options to the API too.

Bill

7

Hi Bill,

regarding the transactionTimeout, we will support this with the next version of both APIs.
For the other options, you mentioned, we are currently investigating them.

Best regards,
Christian.