protoc-gen-bq-schema is a plugin for ProtocolBuffer compiler. It converts messages written in .proto format into schema files in JSON for BigQuery. So you can reuse existing data definitions in .proto for BigQuery with this plugin.

go get github.com/GoogleCloudPlatform/protoc-gen-bq-schema

protoc --bq-schema_out=path/to/outdir foo.proto

protoc and protoc-gen-bq-schema commands must be found in $PATH.

The generated JSON schema files are suffixed with .schema and their base names are named after their package names and bq_table_name options.

If you do not already have the standard google protobuf libraries in your proto_path, you'll need to specify them directly on the command line (and potentially need to copy bq_schema.proto into a proto_path directory as well), like this:

protoc --bq-schema_out=path/to/out/dir foo.proto --proto_path=. --proto_path=<path_to_google_proto_folder>/src

Suppose that we have the following foo.proto.

syntax = "proto2";
package foo;
import "bq_table.proto";
import "bq_field.proto";

message Bar {
  option (gen_bq_schema.table_name) = "bar_table";

  message Nested {
    repeated int32 a = 1;
  }

  required int32 a = 1;
  optional Nested b = 2;
  repeated string c = 3;

  optional bool d = 4 [(gen_bq_schema.bigquery).ignore = true];
  optional uint64 e = 5 [
    (gen_bq_schema.bigquery) = {
      require: true
      type_override: 'TIMESTAMP'
    }
  ];
}

message Baz {
  required int32 a = 1;
}

protoc --bq-schema_out=. foo.proto will generate a file named foo/bar_table.schema. The message foo.Baz is ignored because it doesn't have option gen_bq_schema.table_name.

protoc-gen-bq-schema is licensed under the Apache License version 2.0. This is not an official Google product.