• Sean McGivern's avatar
    Avoid hitting statement timeout finding MR pipelines · 4ccf1ee1acdf
    Sean McGivern authored
    For MRs with many thousands of commits, `SELECT DISTINCT(sha)` will be very
    slow.
    
    What we can't do to fix this:
    
    1. Add an index. Postgres won't use it for DISTINCT without a lot of ceremony.
    2. Do the `uniq` in Ruby. That can still be very slow with hundreds of
       thousands of commits.
    3. Use a subquery. We haven't removed the `st_commits` column yet, but we will
       soon.
    
    Until 3 is available to us, we can just do 2, but also add a limit clause. There
    is no ordering, so this may return different results, but our goal with these
    MRs is just to get them to load, so it's not a huge deal.
    4ccf1ee1acdf