Hi I'd like to propose a relaxation on the Version API. Uwe, please read the entire email before you reply :).
I was thinking, following a question on the user list, that the Version-based API may not be very intuitive to users, especially those who don't care about versioning, as well as very inconvenient. So there are two issues here: 1) How should one use Version smartly so that he keeps backwards compatibility. I think we all know the answer, but a Wiki page with some "best practices" tips would really help users use it. 2) How can one write sane code, which doesn't pass versions all over the place if: (1) he doesn't care about versions, or (2) he cares, and sets the Version to the same value in his app, in all places. Also, I think that today we offer a flexibility to users, to set different Versions on different objects in the life span of their application - which is a good flexibility but can also lead people to shoot themselves in the legs if they're not careful -- e.g. upgrading Version across their app, but failing to do so for one or two places ... So the change I'd like to propose is to mostly alleviate (2) and better protect users - I DO NOT PROPOSE TO GET RID OF Version :). I was thinking that we can add on Version a DEFAULT version, which the caller can set. So Version.setDefault and Version.getDefault will be added, as static members (more on the static-ness of it later). We then change the API which requires Version to also expose an API which doesn't require it, and that API will call Version.getDefault(). People can use it if they want to ... Few points: 1) As a default DEFAULT Version is controversial, I don't want to propose it, even though I think Lucene can define the DEFAULT to be the latest. Instead, I propose that Version.getDefault throw a DefaultVersionNotSetException if it wasn't set, while an API which relies on the default Version is called (I don't want to return null, not sure how safe it is). 2) That DEFAULT Version is static, which means it will affect all indexing code running inside the JVM. Which is fine: 2.1) Perhaps all the indexing code should use the same Version 2.2) If you know that's not the case, then pass Version to the API which requires it - you cannot use the 'default Version' API -- nothing changes for you. One case is missing -- you might not know if your code is the only indexing code which runs in the JVM ... I don't have a solution to that, but I think it'll be revealed pretty quickly, and you can change your code then ... So to summarize - the current Version API will remain and people can still use it. The DEFAULT Version API is meant for convenience for those who don't want to pass Version everywhere, for the reasons I outlined above. This will also clean our test code significantly, as the tests will set the DEFAULT version to TEST_VERSION_CURRENT at start ... The changes to the Version class will be very simple. If people think that's acceptable, I can open an issue and work on it. Shai
