Merge lp:~adeuring/lazr.batchnavigator/lazr.batchnavigator-result-length-from-range-factory into lp:lazr.batchnavigator

[Abel Deuring]

This branch is another (hopefully the last...) step to prepare lazr.batchnavigator for usage in combination with StormRangeFactory.

One time out problem are the SELECT count(*) queries we need in batched views, just to show a text like "10 -> 19 of 1209 results" in a batched view.

lifeless suggested to use "EXPLAIN SELECT..." instead; the result is not necessarily precise but should be "good enough" as an indicator. Some older revisions of lazr.batchnavigator already make sure that the length of the result set is not used for any other purpose in lazr.batchnavigator, like determining if the end of the result set has been reached.

The class _Batch has a cached property listlength, which calls either len(resultset) or len(IFiniteSequence(resultset)); the IFiniteSequenceAdapter for Storm result sets issues the SELECT count(*) query.

The core of this branch is simply to let _Batch.list_length retrieve the length of the resultset from its range factory: IRangeFactories already handle all other access to a resultset for _Batch, and they are supposed to "know best" how to access the result set efficiently.

[Aaron Bentley (abentley)]

Aside from some typos discussed on IRC, this is good to land. You may wish to change the result_length member to "rough_length" or "approx_length".

review: Approve

[lp:~adeuring/lazr.batchnavigator/lazr.batchnavigator-result-length-from-range-factory]

52. By Abel Deuring on 2011-09-07

IRangeFactory.result_length renamed to rough_length; typos fixed.