Le 25/06/2020 à 12:18, Antoine Pitrou a écrit : > > Le 25/06/2020 à 00:40, Wes McKinney a écrit : >> hi folks, >> >> This has come up in some other contexts, but I believe it would be a >> good idea to increment the version number in Schema.fbs starting with >> 1.0.0 to separate the pre-1.0 and post-1.0 worlds >> >> https://github.com/apache/arrow/blob/master/format/Schema.fbs#L22 >> >> Given that we are contemplating a number of changes to assist with >> forward compatibility and a breaking serialization change for unions, >> this would seem prudent so that we do not risk breaking compatibility >> with 0.17.1 and prior. >> >> Given that there are no major backwards incompatibilities, there >> should be no problem with 1.0.0 readers reading data generated by >> libraries <= 0.17.1. > > Actually, it seems that a dense array with top-level null values > (represented in 0.17.1 fashion) would need non-trivial rewriting of its > offsets and child arrays (at least one child array) to represent the > nulls at the child level. > > This is unless we keep the top-level union null bitmap in C++ and only > avoid emitting it on the IPC side. Which would be a slightly weird > arrangement, but would limit incompatibilites on the C++ API side.
Actually, if we do this, the same problem will appear on the IPC write side (C++-created dense union arrays with a top-level null bitmap will need regenerating some of the child buffers). Regards Antoine.
