gaodayue commented on issue #1684: [Proposal] Bitmap Index File Format for V2 segment URL: https://github.com/apache/incubator-doris/issues/1684#issuecomment-526113327 @kangpinghuang > Can we write bitmap index of each column into a independent file, named with column_id in its name, eg: segment_name.1.bitmap is the bitmap index file for column 1. So we can add index for a column easily and drop index file directly when delete index. And we can keep the generated file immutable. The shortcome is that it will open more files and incur more IO when load multiple columns simultaneously, But compared to the data size and with page cache, maybe it can be ignored. I think the independent file approach brings more troubles than benefits. If you have a table with many indexed column (which is very common in OLAP), you end up with many small index files to open and read, which will hurt read performance. The biggest advantage is drop index operation can delete the index file right away, but that operation is less frequent than add index IMO and marked delete in other approaches isn't necessarily bad.
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