Fix the gc with indirect self-references via the realisations

If the derivation `foo` depends on `bar`, and they both have the same
output path (because they are CA derivations), then this output path
will depend both on the realisation of `foo` and of `bar`, which
themselves depend on each other.
This confuses SQLite which isn’t able to automatically solve this
diamond dependency scheme.

Help it by adding a trigger to delete all the references between the
relevant realisations.

Fix #5320
This commit is contained in:
regnat 2021-11-03 16:30:22 +01:00 committed by Théophane Hufschmitt
parent 6ada496311
commit 92656da0b9
2 changed files with 27 additions and 1 deletions

View file

@ -13,6 +13,19 @@ create table if not exists Realisations (
create index if not exists IndexRealisations on Realisations(drvPath, outputName); create index if not exists IndexRealisations on Realisations(drvPath, outputName);
-- We can end-up in a weird edge-case where a path depends on itself because
-- its an output of a CA derivation, that happens to be the same as one of its
-- dependencies.
-- In that case we have a dependency loop (path -> realisation1 -> realisation2
-- -> path) that we need to break by removing the dependencies between the
-- realisations
create trigger if not exists DeleteSelfRefsViaRealisations before delete on ValidPaths
begin
delete from RealisationsRefs where realisationReference = (
select id from Realisations where outputPath = old.id
);
end;
create table if not exists RealisationsRefs ( create table if not exists RealisationsRefs (
referrer integer not null, referrer integer not null,
realisationReference integer, realisationReference integer,

View file

@ -81,7 +81,7 @@ int getSchema(Path schemaPath)
void migrateCASchema(SQLite& db, Path schemaPath, AutoCloseFD& lockFd) void migrateCASchema(SQLite& db, Path schemaPath, AutoCloseFD& lockFd)
{ {
const int nixCASchemaVersion = 3; const int nixCASchemaVersion = 4;
int curCASchema = getSchema(schemaPath); int curCASchema = getSchema(schemaPath);
if (curCASchema != nixCASchemaVersion) { if (curCASchema != nixCASchemaVersion) {
if (curCASchema > nixCASchemaVersion) { if (curCASchema > nixCASchemaVersion) {
@ -143,6 +143,19 @@ void migrateCASchema(SQLite& db, Path schemaPath, AutoCloseFD& lockFd)
)"); )");
txn.commit(); 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 = (
select id from Realisations where outputPath = old.id
);
end;
)");
txn.commit();
}
writeFile(schemaPath, fmt("%d", nixCASchemaVersion)); writeFile(schemaPath, fmt("%d", nixCASchemaVersion));
lockFile(lockFd.get(), ltRead, true); lockFile(lockFd.get(), ltRead, true);
} }