Expose CSV options to Go

[tebeka]

The arrow CSV package has the following options: ReadOptions, ParseOptions & ConvertOptions. Expose them to Go.

[tebeka]

Maybe use functional options

[tebeka]

Problem

These option structs are C++ structs, they have a static Defaults function that
returns a struct (not pointer). When creating an arrow::csv::Reader you need
to pass options by reference.

cgo can’t work directly with C++, which means we can use them directly as
C.ParseOptions.

Possible Solutions

new function

A C function that will get all the parameters for an options struct and create
it.

Problems

• Need to update the function every time options struct is updated at the C++
  level
• Probably need to be part of making a reader since we need to pass the struct
  by reference
• A lot of parameters¹, since we have several such options struct

Use Pointers

Have C wrappers that will create a pointer to options struct and have setters.

Problems

• Who frees the memory?
• A lot of setter functions
• Extra memory allocation

C Shadow struct

Have a C struct that will be a copy of the C++ struct. Can be used directly
from Go and passed around by value.

Problems

• Need to be in par with C++
• Duplication (code & memory)
  • Since it’s a creator function, don’t see memory as a bit problem

SWIG

Use swig to generate wrappers.

Problems

• Learning curve
• Looks like need to be more systematic approach
• Not sure how it’ll work with C++ calling into Go (GoStream class)

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1: If you have a procedure with 10 parameters, you probably missed some. - Alan Perlis

[tebeka]

@yonidavidson Care to weigh in on the above?

[yonidavidson]

This can be a good POC for SWIG, yet I don't think SWIG will be our silver bullet so It might not be worth to add complexity to our system with it.
I think a functional API is a good choice, it gives you an ability to have a good default and to expose the parameters in a need to have way (easy to extend).

[tebeka]

I'll probably go with C shadow struct for now. I'll defer SWIG for when we go all-in on it.