twitter: Batch writes of data to postgres

[adamdecaf]

It's way better to be batching these inserts rather than one at a time writes.

[adamdecaf]

Links:

• https://godoc.org/github.com/lib/pq#hdr-Bulk_imports
• https://stackoverflow.com/questions/21108084/golang-mysql-insert-multiple-data-at-once/21112176#21112176