db-migration-problems: change an enum, split a table, add a foreign key - #12
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…d a foreign key change-an-enum: widening the CHECK is instant; the first WRITE of the new value is the migration, and the shortcut writes it while r1 still reads. split-a-table: dual write and backfill; the shortcut switches reads once the backfill has started — five steps, the longest route in the collection. add-a-foreign-key: NOT VALID spares the old rows, not the running code; adding it mid-rollout makes the old release's deletes fail, in two steps. writ sql reads CHECK … IN as an enum and REFERENCES as an arrow, as planned; it reads NOT VALID as a plain foreign key (identical output, --strict accepts it) while declining VALIDATE CONSTRAINT — asserted as found. The parent README's "the shortcut is always shorter" is now what was measured: shorter in two of six, never longer. Cross-check 57 -> 63 properties (61 compared); 305 checks. Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
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Stacked on #11 (base
on-call-rota). Retarget tomainonce #11 merges.Adds the second batch of
db-migration-problems/: three directories built to the first batch's standard. Each has SQL steps read bywrit sql, a safe plan, a shortcut and a README.change-an-enum/'archived'while r1, which cannot read it, still servesadd-value → deploy-r2 → archive-t1split-a-table/add-a-foreign-key/NOT VALIDmid-rollout, so the old code's deletes now faildeploy-r2 → add-not-validwrit sqlfindings, asserted as they are:CHECK … INbecomes an enumerated type, andREFERENCESbecomes(fk …), as planned.NOT VALIDis read as an ordinary foreign key. The output is identical with or without it,--strictaccepts it, and an orphan row in that file loads without complaint.VALIDATE CONSTRAINTis declined under--strict, so the clause that changes meaning is the one accepted silently. Worth a writ issue:--strictcould declineNOT VALIDtoo, since writ carries a constraint's presence, not its validation state.A correction to the parent README: "the shortcut is always shorter" was not measured. Over all six, the shortest route to a finished migration is shorter in two (
add-a-required-column3 vs 5,rename-a-column8 vs 9) and equal in four. The README now says "never slower", with the numbers.comparereports nothing LOST for any of the six, socheckis the gate.Cross-check: 57 → 63 properties (61 compared).
./run-tests.sh all: 305 checks, 0 failed.🤖 Generated with Claude Code