Good to have a little time again to hack Cayenne internals.
Just committed a pretty big change to the prefetching algorithm
motivated by CAY-1250 bug report. So combining prefetching and
inheritance now works 100%.
One visible effect of this change is that all disjoint prefetch
queries will now include the ID's of the source side of the prefetch
relationship and a mandatory join to the source entity. In return for
this small inefficiency (increased result set size... hopefully most
ID's are small), we get a bunch of benefits, main one being the
ability to process related fetched objects in a consistent manner
regardless of the relationship semantics (1..1, 1..N, N..M). This
strategy was used before for flattened relationships, now it is used
for everything. On the other hand this change allowed to optimize some
related cases, so all in all, there may be no performance penalty.
It is still possible to go back and optimize it further to prevent the
addition of the extra columns to the resultset in some cases (e.g. if
both joined FK and PK are present in the result, only fetch one of
them), I wish we could do that in some central location (like
SelectTranslator) instead of writing endless if/else in the prefetch
processing code.
Now the prefetch code is easier to make sense of, with fewer if/else.
And I am planning to refactor it further.
Also I came very close to fixing the biggest remaining limitation of
disjoint prefetching:
https://issues.apache.org/jira/browse/CAY-1025
Andrus
This archive was generated by hypermail 2.0.0 : Sun Sep 06 2009 - 21:43:41 EDT