implement DeleteReplica on RepositoryStore

RepositoryStore has DeleteRepository for deleting a repository from
the store. It deletes the repository's record from the `repositories`
table to indicate the repository should not exist on any storages
anymore. It then also deletes the storage's record of having a replica
of the repository. This works fine for the flow where it is currently
called, namely when Rails deletes a repository. In that case, the
deletion should be replicated everywhere and we should delete any
records of it from the database.

Reconciler is gaining support for deleting repositories from storages
which should not contain them anymore. In this case, we only want to
delete the replica of the repository on a given storage. We don't want
to replicate the deletion anywhere else nor do we want to delete the
repository's entry in `repositories` table as the repository should
still exist and be accessible via other storages. To support this use
case, this commit introduces a DeleteReplica method on the Repository
Store to delete a record of a replica from a given storage without
affecting any other state in the database.

3 files changed, 104 insertions, 3 deletions

diff --git a/internal/praefect/datastore/repository_store.go b/internal/praefect/datastore/repository_store.go
index bc2c8c8ba..4ed5abe54 100644
--- a/internal/praefect/datastore/repository_store.go
+++ b/internal/praefect/datastore/repository_store.go
@@ -111,6 +111,8 @@ type RepositoryStore interface {
 	// RepositoryNotExistsError when trying to delete a repository which has no record in the virtual storage
 	// or the storage.
 	DeleteRepository(ctx context.Context, virtualStorage, relativePath, storage string) error
+	// DeleteReplica deletes a replica of a repository from a storage without affecting other state in the virtual storage.
+	DeleteReplica(ctx context.Context, virtualStorage, relativePath, storage string) error
 	// RenameRepository updates a repository's relative path. It renames the virtual storage wide record as well
 	// as the storage's which is calling it. Returns RepositoryNotExistsError when trying to rename a repository
 	// which has no record in the virtual storage or the storage.
@@ -355,7 +357,7 @@ VALUES ($1, $2, $3, 0)
 }
 
 func (rs *PostgresRepositoryStore) DeleteRepository(ctx context.Context, virtualStorage, relativePath, storage string) error {
-	const q = `
+	return rs.delete(ctx, `
 WITH repo AS (
 	DELETE FROM repositories
 	WHERE virtual_storage = $1
@@ -366,9 +368,23 @@ DELETE FROM storage_repositories
 WHERE virtual_storage = $1
 AND relative_path = $2
 AND storage = $3
-`
+		`, virtualStorage, relativePath, storage,
+	)
+}
+
+// DeleteReplica deletes a record from the `storage_repositories`. See the interface documentation for details.
+func (rs *PostgresRepositoryStore) DeleteReplica(ctx context.Context, virtualStorage, relativePath, storage string) error {
+	return rs.delete(ctx, `
+DELETE FROM storage_repositories
+WHERE virtual_storage = $1
+AND relative_path = $2
+AND storage = $3
+		`, virtualStorage, relativePath, storage,
+	)
+}
 
-	result, err := rs.db.ExecContext(ctx, q, virtualStorage, relativePath, storage)
+func (rs *PostgresRepositoryStore) delete(ctx context.Context, query, virtualStorage, relativePath, storage string) error {
+	result, err := rs.db.ExecContext(ctx, query, virtualStorage, relativePath, storage)
 	if err != nil {
 		return err
 	}
diff --git a/internal/praefect/datastore/repository_store_mock.go b/internal/praefect/datastore/repository_store_mock.go
index 8df265ef5..13dcd2eab 100644
--- a/internal/praefect/datastore/repository_store_mock.go
+++ b/internal/praefect/datastore/repository_store_mock.go
@@ -11,6 +11,7 @@ type MockRepositoryStore struct {
 	SetGenerationFunc                      func(ctx context.Context, virtualStorage, relativePath, storage string, generation int) error
 	CreateRepositoryFunc                   func(ctx context.Context, virtualStorage, relativePath, primary string, secondaries []string, storePrimary, storeAssignments bool) error
 	DeleteRepositoryFunc                   func(ctx context.Context, virtualStorage, relativePath, storage string) error
+	DeleteReplicaFunc                      func(ctx context.Context, virtualStorage, relativePath, storage string) error
 	RenameRepositoryFunc                   func(ctx context.Context, virtualStorage, relativePath, storage, newRelativePath string) error
 	GetConsistentStoragesFunc              func(ctx context.Context, virtualStorage, relativePath string) (map[string]struct{}, error)
 	GetPartiallyReplicatedRepositoriesFunc func(ctx context.Context, virtualStorage string, virtualStorageScopedPrimaries bool) ([]OutdatedRepository, error)
@@ -68,6 +69,15 @@ func (m MockRepositoryStore) DeleteRepository(ctx context.Context, virtualStorag
 	return m.DeleteRepositoryFunc(ctx, virtualStorage, relativePath, storage)
 }
 
+// DeleteReplica runs the mock's DeleteReplicaFunc.
+func (m MockRepositoryStore) DeleteReplica(ctx context.Context, virtualStorage, relativePath, storage string) error {
+	if m.DeleteReplicaFunc == nil {
+		return nil
+	}
+
+	return m.DeleteReplicaFunc(ctx, virtualStorage, relativePath, storage)
+}
+
 func (m MockRepositoryStore) RenameRepository(ctx context.Context, virtualStorage, relativePath, storage, newRelativePath string) error {
 	if m.RenameRepositoryFunc == nil {
 		return nil
diff --git a/internal/praefect/datastore/repository_store_test.go b/internal/praefect/datastore/repository_store_test.go
index 365260a03..acbe3f3c7 100644
--- a/internal/praefect/datastore/repository_store_test.go
+++ b/internal/praefect/datastore/repository_store_test.go
@@ -474,6 +474,81 @@ func testRepositoryStore(t *testing.T, newStore repositoryStoreFactory) {
 		})
 	})
 
+	t.Run("DeleteReplica", func(t *testing.T) {
+		rs, requireState := newStore(t, nil)
+
+		t.Run("delete non-existing", func(t *testing.T) {
+			require.Equal(t,
+				RepositoryNotExistsError{"virtual-storage-1", "relative-path-1", "storage-1"},
+				rs.DeleteReplica(ctx, "virtual-storage-1", "relative-path-1", "storage-1"),
+			)
+		})
+
+		t.Run("delete existing", func(t *testing.T) {
+			require.NoError(t, rs.SetGeneration(ctx, "virtual-storage-1", "relative-path-1", "storage-1", 0))
+			require.NoError(t, rs.SetGeneration(ctx, "virtual-storage-1", "relative-path-1", "storage-2", 0))
+			require.NoError(t, rs.SetGeneration(ctx, "virtual-storage-1", "relative-path-2", "storage-1", 0))
+			require.NoError(t, rs.SetGeneration(ctx, "virtual-storage-2", "relative-path-1", "storage-1", 0))
+
+			requireState(t, ctx,
+				virtualStorageState{
+					"virtual-storage-1": {
+						"relative-path-1": repositoryRecord{},
+						"relative-path-2": repositoryRecord{},
+					},
+					"virtual-storage-2": {
+						"relative-path-1": repositoryRecord{},
+					},
+				},
+				storageState{
+					"virtual-storage-1": {
+						"relative-path-1": {
+							"storage-1": 0,
+							"storage-2": 0,
+						},
+						"relative-path-2": {
+							"storage-1": 0,
+						},
+					},
+					"virtual-storage-2": {
+						"relative-path-1": {
+							"storage-1": 0,
+						},
+					},
+				},
+			)
+
+			require.NoError(t, rs.DeleteReplica(ctx, "virtual-storage-1", "relative-path-1", "storage-1"))
+
+			requireState(t, ctx,
+				virtualStorageState{
+					"virtual-storage-1": {
+						"relative-path-1": repositoryRecord{},
+						"relative-path-2": repositoryRecord{},
+					},
+					"virtual-storage-2": {
+						"relative-path-1": repositoryRecord{},
+					},
+				},
+				storageState{
+					"virtual-storage-1": {
+						"relative-path-1": {
+							"storage-2": 0,
+						},
+						"relative-path-2": {
+							"storage-1": 0,
+						},
+					},
+					"virtual-storage-2": {
+						"relative-path-1": {
+							"storage-1": 0,
+						},
+					},
+				},
+			)
+		})
+	})
+
 	t.Run("RenameRepository", func(t *testing.T) {
 		t.Run("rename non-existing", func(t *testing.T) {
 			rs, _ := newStore(t, nil)