Is affinity() supposed to return a Pair{OSProc, UInt64} or a Vector{Pair{OSProc, UInt64}}?

[mattwigway]

The definition of affinity for a DRef returns a pair, while the definition for a FileRef returns a singleton Vector{Pair}. This is causing a boundserror in Sch.jl which calls affinity(...)[2] and crashes when affinity returns a singleton vector. This is causing the tests for JuliaDB to fail on Julia 1.7 (though they work on earlier versions, perhaps those versions are using the DRef codepath). Based on the code it seems like affinity should return a Pair rather than a Vector{Pair}, but wanted to confirm before making a PR.

[mattwigway]

cc JuliaData/JuliaDB.jl#389 and JuliaData/JuliaDB.jl#404

[jpsamaroo]

Yeah, I chose to change the definition of affinity() for #221 because I felt that returning affinities for every worker who might have the DRef cached would be excessive (even though the old definition didn't actually do that, but it should have to fulfill the contract of affinity()). FileRef should probably be updated to just return a single pair for the owner. Note that #289 will probably end up using its own variant of FileRef, and may obviate the need for JuliaDB to know anything about where data resides (in-memory, on disk, etc.).

I'd be happy to accept a PR adjusting affinity(::FileRef) to just return a single pair, OSProc(1) => size, since we don't currently use the first item of the pair anyway.

[mattwigway]

Great, will prepare a PR.