fix wrong result with WrappedImmutableConciseBitmap#difference, issue…

[lushuifeng]

#40 for details, please take a look, thanks

[lemire]

Why is the difference implemented as the intersection with the complement when there is an andNot method that would be (no doubt) more efficient and simpler?

[lushuifeng]

I do not think andNot method is exist in ImmutableBitmap, I would perfer using andNot method if there is one. The bitmap is deserialized from file content which is ImmutableBitmap, and then a lot of and, or, andNot is performed on ImmutableBitmap

[lemire]

Please see https://github.com/RoaringBitmap/RoaringBitmap/blob/master/roaringbitmap/src/main/java/org/roaringbitmap/buffer/ImmutableRoaringBitmap.java Search andNot.

[lushuifeng]

there is one in ImmutableRoaringBitmap but not in ImmutableConciseBitmap, when it comes to ImmutableConciseBitmap#difference method, no better function call I've found. the type of bitmap(roaring or concise) is deserialized from file which is not fixed

[lemire]

Ok. Thanks, I understand.

[lushuifeng]

thanks

[gianm]

Hi @lushuifeng, is this related to an issue you have noticed with Druid? If so, could you please raise this as a patch in the druid-io/druid repo? We have incorporated this code into Druid itself, so this library is no longer used.

[lushuifeng]

Sorry, not yet. It seems that this method is not invoked in druid, not deep into this

[lushuifeng]

latest version is not checked, verson 0.9.3 seems ok.

[lushuifeng]

It should work in latest druid, the filters and bitmapFactory implementations do not involve with this issue. BTW, how can I use the latest bitmap dependency since this is incorporated into druid?

[gianm]

The Druid libraries are on Maven Central so you could include them from there.