Cleanup: Remove migrations for ancient CA schemas

These versions are more than 3 years old and were very early in the
existence of CA derivations support (which was and is experimental),
so they're unlikely to still exist in the real world. So let's get rid
of support for them.

src/libstore/local-store.cc

@@ -93,7 +93,7 @@ struct LocalStore::State::Stmts {
  SQLiteStmt AddRealisationReference;
 };
 
-int getSchema(Path schemaPath)
+static int getSchema(Path schemaPath)
 {
  int curSchema = 0;
  if (pathExists(schemaPath)) {
@@ -130,61 +130,8 @@ void migrateCASchema(SQLite& db, Path schemaPath, AutoCloseFD& lockFd)
  curCASchema = nixCASchemaVersion;
  }
 
- if (curCASchema < 2) {
- SQLiteTxn txn(db);
- // Ugly little sql dance to add a new `id` column and make it the primary key
- db.exec(R"(
- create table Realisations2 (
- id integer primary key autoincrement not null,
- drvPath text not null,
- outputName text not null, -- symbolic output id, usually "out"
- outputPath integer not null,
- signatures text, -- space-separated list
- foreign key (outputPath) references ValidPaths(id) on delete cascade
- );
- insert into Realisations2 (drvPath, outputName, outputPath, signatures)
- select drvPath, outputName, outputPath, signatures from Realisations;
- drop table Realisations;
- alter table Realisations2 rename to Realisations;
- )");
- db.exec(R"(
- create index if not exists IndexRealisations on Realisations(drvPath, outputName);
-
- create table if not exists RealisationsRefs (
- referrer integer not null,
- realisationReference integer,
- foreign key (referrer) references Realisations(id) on delete cascade,
- foreign key (realisationReference) references Realisations(id) on delete restrict
- );
- )");
- txn.commit();
- }
-
- if (curCASchema < 3) {
- SQLiteTxn txn(db);
- // Apply new indices added in this schema update.
- db.exec(R"(
- -- used by QueryRealisationReferences
- create index if not exists IndexRealisationsRefs on RealisationsRefs(referrer);
- -- used by cascade deletion when ValidPaths is deleted
- create index if not exists IndexRealisationsRefsOnOutputPath on Realisations(outputPath);
- )");
- txn.commit();
- }
- if (curCASchema < 4) {
- SQLiteTxn txn(db);
- db.exec(R"(
- create trigger if not exists DeleteSelfRefsViaRealisations before delete on ValidPaths
- begin
- delete from RealisationsRefs where realisationReference in (
- select id from Realisations where outputPath = old.id
- );
- end;
- -- used by deletion trigger
- create index if not exists IndexRealisationsRefsRealisationReference on RealisationsRefs(realisationReference);
- )");
- txn.commit();
- }
+ if (curCASchema < 4)
+ throw Error("experimental CA schema version %d is no longer supported", curCASchema);
 
  writeFile(schemaPath, fmt("%d", nixCASchemaVersion), 0666, true);
  lockFile(lockFd.get(), ltRead, true);