We have several deprecated methods in Cell interface, like getSequenceId and tag related ones, which are marked as deprecated since 2.0.0 and should be removed in 3.0.0. Most of them are marked as deprecated in HBASE-19112.
After investigating, I found that it is not an easy work... We have 3 levels for the Cell interface Cell -> RawCell -> ExtendedCell Where Cell is the Public API for client side usage, RawCell is for CPs where we expose the tag related APIs, and ExtendedCell is for server side usage, where we expose all the internal stuff, like sequence id. In HBASE-19550, we introduced a CellWrapper as we think maybe CPs will return a Cell which is not an ExtendedCell at server side, we need to wrap it so at server side we always get an ExtendedCell. So if we remove the tag and sequence id related methods, CellWrapper will be broken. For me, I do not think we need the CellWrapper. In general, all actual Cell implementation classes in our code base implement the ExtendedCell interface, i.e, we can simply consider all Cells are actually ExtendedCells. The only reason we introduce the Cell interface, is to hide internal stuff from client public API, does not mean we want users to implement their own Cell. So the plan is to change server side code use ExtendedCell as much as possible in HBASE-28644, a draft PR is already there for review[1]. This will be landed to both 3.x and at least branch-2(I'm not sure if it worth to also land on branch-2.6 and branch-2.5). And starting from 3.0.0, we should make clear that all Cell instances should be created via the CellBuilder related APIs, other Cell implementations are not allowed. So on 3.0.0, we should treat Cell as ExtendedCell everywhere in our code base, and also remove the CellWrapper class, then we could finally remove the deprecated methods in the Cell interface. Thoughts? Thanks. 1. https://github.com/apache/hbase/pull/5976
