Ensure Deterministic Migration Order #4136
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aoengin wants to merge 4 commits intolaunchbadge:mainfrom
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abonander
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May 1, 2026
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| migrations.sort_by(|a, b| { | ||
| a.version.cmp(&b.version).then_with(|| { | ||
| a.migration_type | ||
| .direction_order() | ||
| .cmp(&b.migration_type.direction_order()) | ||
| }) | ||
| }); |
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We should just implement PartialOrd and Ord for Migration and then this can just be migrations.sort().
| } | ||
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| /// Ordering helper to sort ups before downs when versions tie. | ||
| pub fn direction_order(&self) -> u8 { |
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Just add #[derive(PartialOrd, Ord)] for MigrationType. It'd be a degenerate case, but Simple and ReversibleUp comparing equal could still result in nondeterminism.
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Migration equality and ordering are based on identity, not full content. A (version, migration_type) pair represents one logical migration slot. |
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What / why
When embedding migrations into the binary via
migrate!, the iteration order of migration files can vary across filesystems/OSes. That makes the resulting embedded migration list (and thus the final binary) non-deterministic, which breaks reproducible builds.This PR makes migration ordering deterministic by explicitly ordering reversible migration pairs so that
upis always beforedownfor the same migration version.Changes
Add
MigrationType::direction_order()to define a stable tie-break rule (up/simplefirst,downsecond).Update
Migrator::with_migrations()to sort migrations by:direction_order()for version ties.Apply the same deterministic sort when resolving migrations from a source (blocking resolver).
Impact