Discogs to PostgreSQL

Import Discogs' data dumps into Postgres efficiently.

Uses Hexpat for parsing XML and Postgres' COPY to store the result.

Inspired by discogs-xml2db.

Why?

I wanted Discogs' data in a Postgres database and I had some issues with the existing solution:

1. it was slow, I let it run for 5 hours and it didn't finish
2. SAX events parsing for nested data is too difficult to maintain IMHO
3. using INSERT is not efficient, and I didn't want UNLOGGED tables
4. I wanted some data it didn't import and didn't want some it did
5. performance, I wanted it to be fast on commodity hardware

Installation

The projects uses stack so it should be as easy as:

stack install

and adding stack's binary path to your PATH (if you haven't already).

Usage

Supposing we downloaded the 20150810 dump:

• discogs_20150810_artists.xml.gz
• discogs_20150810_labels.xml.gz
• discogs_20150810_masters.xml.gz
• discogs_20150810_releases.xml.gz

and we didn't decompress them, then we can run on the repo's directory:

$ createdb discogs
$ psql discogs < sql/tables.sql
$ discogs2pg -g -d 20150810 -c dbname=discogs
$ # wait an hour or two ...
$ psql discogs < sql/indexes.sql

Options

discogs2pg can has two forms of operation, by file and by date.

You can import a single file with discogs2pg -c <blah> some_releases.xml or import releases, artists, labels and master for a date DATE in the current directory with discogs2pg -c <blah> -d DATE.

Also the -g | --gzip option lets you import the compressed files directly.

If you want it to be even faster, and your computer can handle it, you can pass an optional --aggressive to make it open all file in parallel. Consider that since we are using COPY it will open a connection per table: that's 15 connections at once.

Contributing

I don't have a Windows machine to build and test the binary, so I'd love it if someone could get into that.

Also, I can think of two things:

• someone with experience in DBs could improve the data structure and indexes/primary keys
• someone with experience in structuring Haskell projects could help with the types/typeclasses and modules
• the code uses lazy lists (for real), I'd like to refactor it with conduit or something

I'd be glad to hear suggestions and take pull requests, of course.