@Minghong We'll use a multi-version delete bitmap, only save delta for each version. For example, we have a rowset with version [0-98], transaction 99 updated some row in that rowset, and so does transaction 100 and 101, there would be 3 delete bitmaps on that rowset, corresponding to rows updated by version 99, 100 and 101. A query with version x will only see the bitmap up to version x. There's more details about space saving and cache acceleration, let's discuss it in DSIP.
@Xiaoli, our team have finished most develop works for the basic function in our private repository, but there‘s still lots of works to do, welcome to get involve. @Mingyu, could you help to create a DISP doc? I don't seem to have permission. Best Chen Zhang On Jun 23, 2022, 21:41 +0800, Zhou Minghong <minghong.z...@163.com>, wrote: > Hi Chen Zhang > one question about "and a delete bitmap (marks some rowid as deleted)”： > how to handle transaction information by a bitmap? > for example, transaction_100 delete a row, but this still visible to > transaction_99, but not visible to trasanction_101. How to handle this case? > > > Br/Minghong > > > > > > > > > > > > > > > > > > At 2022-06-23 19:14:58, "Zhu,Xiaoli" <zhuxiaol...@baidu.com> wrote: > > Hi Chen Zhang, > > > > I am very interested in this topic, and want to participate in the > > development. > > > > 在 2022/6/23 下午2:44，“Chen Zhang”<chzhang1...@gmail.com> 写入: > > > > Hi devs, > > > > Unique-Key data model is widely used in scenarios like Flink-CDC, user > > profile(用户画像), E-commerce orders, but the query performance for current > > Merge-On-Read implementation is not good, due to the following reasons: > > > > 1. Doris can't determine whether one row in a segment file is latest or > > outdated, so it has to do some extra merge sort before getting the > > latest data, and key comparison is quite CPU-costive. > > 2. Aggregate function predicate push down is not supported by the > > Unique-Key data model due to reason(1). > > > > I'd like to propose to support a Merge-On-Write implementation for the > > Unique-Key data model, which leverages a new segment-file-level primary > > key index (used for point lookup on write) and a delete bitmap (marks some > > rowid as deleted), which can optimize read performance significantly. > > > > At the beginning, we wanted to add another Primary-Key data model with > > Merge-On-Write implementation, but after a lot of discussion, we'd prefer > > to improve the Unique-Key data model rather than adding another one. > > > > I'll add detailed design and related research in the DSIP doc later. > > > > > > --------------------------------------------------------------------- > > To unsubscribe, e-mail: dev-unsubscr...@doris.apache.org > > For additional commands, e-mail: dev-h...@doris.apache.org > >
