Support fine-grained database schema migrations #11668
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Does this also help with the deadlock that are seeing when enabling ca derivations? Currently it requires a reboot of the machine because existing running nix processes will not allow the schema migration from happening as they hold the global lock file. |
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@Mic92 It should help with the deadlock since it doesn't hold the global lock anymore while doing SQLite schema migrations. (Maybe it should, but AFAIK SQLite doesn't need it.) |
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Great that's my main road block to deploy this by default on a larger amount of machines |
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This pull request has been mentioned on NixOS Discourse. There might be relevant details there: https://discourse.nixos.org/t/2024-10-16-nix-team-meeting-minutes-187/54835/1 |
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Backward-compatible schema changes (e.g. those that add tables or nullable columns) now no longer need a change to the global schema file (/nix/var/nix/db/schema). Thus, old Nix versions can continue to access the database. This is especially useful for schema changes required by experimental features. In particular, it replaces the ad-hoc handling of the schema changes for CA derivations (i.e. the file /nix/var/nix/db/ca-schema). Schema versions 8 and 10 could have been handled by this mechanism in a backward-compatible way as well.
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Motivation
Backward-compatible schema changes (e.g. those that add tables or nullable columns) now no longer need a change to the global schema file (
/nix/var/nix/db/schema). Thus, old Nix versions can continue to access the database.This is especially useful for schema changes required by experimental features. In particular, it replaces the ad-hoc handling of the schema changes for CA derivations (i.e. the file
/nix/var/nix/db/ca-schema).Schema versions 8 and 10 could have been handled by this mechanism in a backward-compatible way as well.
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