api: fix /eval/X/builds requiring 5*len(builds)+1 SQL queries #1335
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Prefetch related tables that get fetched as part of serialization to JSON. Drop the `jobsetevals` field since making it efficient is trickier (due to not using DBIx native relationships but instead a many_to_many through a custom table). There is likely a way we could keep it and make it efficient, but I'm not fluent enough in DBIx to know.
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Tested on hydra.nixos.org, fetching /builds for haskell-updates eval ID 1798805. Without change: times out after 15min. Still too slow / too much data for a nixpkgs/trunk eval unfortunately. |
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Tried this out on my personal instance with query log being activated and that works fine 👍 |
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Breaks the nixos-channel-scripts which depend on the https://github.com/NixOS/nixos-channel-scripts/blob/master/mirror-nixos-branch.pl#L103 |
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That way it's possible to observe which queries are fired against the DB from DBIx. This is particularly useful to find out if DBIx correctly prefetches everything it needs or if too much / too few things are loaded, see e.g. NixOS#1335.
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Prefetch related tables that get fetched as part of serialization to JSON. Drop the
jobsetevalsfield since making it efficient is trickier (due to not using DBIx native relationships but instead a many_to_many through a custom table). There is likely a way we could keep it and make it efficient, but I'm not fluent enough in DBIx to know.More context in NixOS/infra#270 . This used to """""work""""" (painfully inefficiently) but stopped working once the hydra.nixos.org got moved to a separate machine, inducing higher latency costs for each of the hundreds of thousands of SQL queries that need to run to generate the JSON output for this API endpoint.