Feature request: variable nodes should allow easy metadata storage

[dehann]

Maybe data can be stored in the softtype definitions, such as proposed in #60

[dehann]

This would be the so-called smalldata interface. Not meant to replace the bigdata interface -- i.e.:

addNode!(fg, :x0, Pose3, smalldata=randn(300))

cc @GearsAD

[dehann]

should be available through the userdata::FactorMetadata interface, maybe under userdata.var_smalldata.

[dehann]

should be considered in the DFG discussions

[dehann]

Hi @GearsAD , know you worked on this a little recently -- just wanted to hear if you had any thoughts on:

add{Variable/Factor}!(...,smalldata=Dict())

with conditions that:

• smalldata dict can be json'ed,
• smalldata remains small in terms of size of bytes,
• use of smalldata will slow the system down (especially as its size increases, but trade-off for ease of use is worth it, and
• smalldata is not a replacement for bigdata which is far more competent at efficiently storing (or locally caching) much larger data blobs.

[dehann]

xref JuliaRobotics/Caesar.jl#268

[dehann]

xref wiki discussion: https://github.com/JuliaRobotics/Caesar.jl/wiki/Data-Design-for-Caesar-RoME-IIF

[dehann]

resolved with DFG upgrade

[dehann]

xref JuliaRobotics/IncrementalInference.jl#783