Experimental Go bindings for substrait

This is work in progress still, things still to do:

• Expression parsing
• Reading in extension yamls
• CI building and testing the implementation
• Serialization/Deserialization of some expression types:
  • IfThen
  • SwitchExpression
  • SingularOrList
  • MultiOrList
  • Cast
  • Nested
  • Subquery
• Serialization/Deserialization of Plan and Relations
  • Plan
  • PlanRel
  • Rel
    • ReadRel
    • FilterRel
    • FetchRel
    • AggregateRel
    • SortRel
    • JoinRel
    • ProjectRel
    • SetRel
    • ExtensionSingleRel
    • ExtensionMultiRel
    • ExtensionLeafRel
    • CrossRel
    • HashJoinRel
    • MergeJoinRel
  • DdlRel
  • WriteRel
  • ExchangeRel
• Plan Building helpers
  • ReadRel
    • NamedScanReadRel
    • VirtualTableReadRel
    • ExtensionTableReadRel
    • LocalFileReadRel
  • FilterRel
  • FetchRel
  • AggregateRel
  • SortRel
  • JoinRel
  • ProjectRel
  • SetRel
  • CrossRel
  • HashJoinRel
  • MergeJoinRel
  • DdlRel
  • WriteRel
  • ExchangeRel

As this is built out, you can expect refactors and other changes to the structure of the package for the time being. The API should not yet be considered stable.

First ensure you have buf installed by following https://docs.buf.build/installation.

Run the following to install the Go plugin for protobuf:

$ go install google.golang.org/protobuf/cmd/protoc-gen-go@latest

Ensure that your GOPATH is on your path:

$ export PATH="$PATH:$(go env GOPATH)/bin"

As long as buf and the Go protobuf plugin are installed, you can simply run go generate to generate the updated .pb.go files. It will generate them by referencing the primary substrait-io repository.

You can then commit the updated files.