fix(db): prevent deadlock in concurrent melt quote locking #1474

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thesimplekid merged 1 commit from fix_psgl_quote_locking into main

2025-12-30 11:41:10 +00:00

thesimplekid commented

2025-12-29 23:30:22 +00:00

(Migrated from github.com)

Each transaction would hold its own quote's lock while waiting for locks held by other transactions, creating a circular wait condition that PostgreSQL would resolve by aborting transactions.

Fix by introducing lock_melt_quote_and_related() which acquires all related quote locks atomically in a single query, ordered by ID. This ensures consistent lock ordering across transactions, eliminating the circular wait condition.

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I followed the code style guidelines
I ran just final-check before committing

When multiple wallets attempt to melt quotes sharing the same request_lookup_id concurrently, the previous two-step locking approach (lock target quote, then lock all related quotes) could cause deadlocks. Each transaction would hold its own quote's lock while waiting for locks held by other transactions, creating a circular wait condition that PostgreSQL would resolve by aborting transactions. Fix by introducing lock_melt_quote_and_related() which acquires all related quote locks atomically in a single query, ordered by ID. This ensures consistent lock ordering across transactions, eliminating the circular wait condition. ### Description  ----- ### Notes to the reviewers  ----- ### Suggested [CHANGELOG](https://github.com/cashubtc/cdk/blob/main/CHANGELOG.md) Updates  #### CHANGED #### ADDED #### REMOVED #### FIXED ---- ### Checklist * [ ] I followed the [code style guidelines](https://github.com/cashubtc/cdk/blob/main/CODE_STYLE.md) * [ ] I ran `just final-check` before committing

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