Slightly rework causal_diff_queue insertion logic #99
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ChrisPenner
approved these changes
Jun 18, 2025
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Overview
@ChrisPenner and I accidentally discovered today that the real culprit behind an
INSERT ON CONFLICT DO NOTHINGintocausal_diff_queueblocking is not due to a row lock taken bySELECT FOR UPDATE, but rather the eagerDELETEof the selected row.So, we decided to simply move the
DELETEcall to after a worker has finished computing a namespace diff, significantly reducing the time window during which a concurrentINSERTmight block.This also lets us implement the "on get contribution diff, if missing, insert into work queue" which is convenient to have for a number of minor reasons, including that we can wipe precomputed diffs out of
namespace_diffswhenever we need to, since we are no longer relying on creating or updating a contribution being the only actions that trigger a diff computation.