dendrite/syncapi/storage/tables/backward_extremities.go
Kegsay 35b7cbd5d8
sql/backwards_extremities: Shift to table format and share code (#985)
* sql/backwards_extremities: Shift to table format and share code

This is an initial cut to reduce boilerplate at the storage layer.
It removes the need for 2x `_table.go` files, one for each DB engine,
replacing it with a single struct which has an interface which
implements the raw SQL statements.

The actual impl sits alongside the interface declaration which is
generally regarded as best practice (though no canonical sources).
Especially in this case where the impl is tiny (functions returning
strings) and relies heavily on the function signatures of the
table struct (for parameters), having the context in the same file
is useful.

* Remove _table redundancy
2020-04-28 15:50:24 +01:00

176 lines
6.4 KiB
Go

// Copyright 2020 The Matrix.org Foundation C.I.C.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package tables
import (
"context"
"database/sql"
"github.com/matrix-org/dendrite/common"
)
// BackwardsExtremitiesStatements contains the SQL statements to implement.
// See BackwardsExtremities to see the parameter and response types.
type BackwardsExtremitiesStatements interface {
Schema() string
InsertBackwardExtremity() string
SelectBackwardExtremitiesForRoom() string
DeleteBackwardExtremity() string
}
type PostgresBackwardsExtremitiesStatements struct{}
func (s *PostgresBackwardsExtremitiesStatements) Schema() string {
return `-- Stores output room events received from the roomserver.
CREATE TABLE IF NOT EXISTS syncapi_backward_extremities (
-- The 'room_id' key for the event.
room_id TEXT NOT NULL,
-- The event ID for the last known event. This is the backwards extremity.
event_id TEXT NOT NULL,
-- The prev_events for the last known event. This is used to update extremities.
prev_event_id TEXT NOT NULL,
PRIMARY KEY(room_id, event_id, prev_event_id)
);
`
}
func (s *PostgresBackwardsExtremitiesStatements) InsertBackwardExtremity() string {
return "" +
"INSERT INTO syncapi_backward_extremities (room_id, event_id, prev_event_id)" +
" VALUES ($1, $2, $3)" +
" ON CONFLICT DO NOTHING"
}
func (s *PostgresBackwardsExtremitiesStatements) SelectBackwardExtremitiesForRoom() string {
return "SELECT DISTINCT event_id FROM syncapi_backward_extremities WHERE room_id = $1"
}
func (s *PostgresBackwardsExtremitiesStatements) DeleteBackwardExtremity() string {
return "DELETE FROM syncapi_backward_extremities WHERE room_id = $1 AND prev_event_id = $2"
}
type SqliteBackwardsExtremitiesStatements struct{}
func (s *SqliteBackwardsExtremitiesStatements) Schema() string {
return `-- Stores output room events received from the roomserver.
CREATE TABLE IF NOT EXISTS syncapi_backward_extremities (
-- The 'room_id' key for the event.
room_id TEXT NOT NULL,
-- The event ID for the last known event. This is the backwards extremity.
event_id TEXT NOT NULL,
-- The prev_events for the last known event. This is used to update extremities.
prev_event_id TEXT NOT NULL,
PRIMARY KEY(room_id, event_id, prev_event_id)
);
`
}
func (s *SqliteBackwardsExtremitiesStatements) InsertBackwardExtremity() string {
return "" +
"INSERT INTO syncapi_backward_extremities (room_id, event_id, prev_event_id)" +
" VALUES ($1, $2, $3)" +
" ON CONFLICT (room_id, event_id, prev_event_id) DO NOTHING"
}
func (s *SqliteBackwardsExtremitiesStatements) SelectBackwardExtremitiesForRoom() string {
return "" +
"SELECT DISTINCT event_id FROM syncapi_backward_extremities WHERE room_id = $1"
}
func (s *SqliteBackwardsExtremitiesStatements) DeleteBackwardExtremity() string {
return "" +
"DELETE FROM syncapi_backward_extremities WHERE room_id = $1 AND prev_event_id = $2"
}
// BackwardsExtremities keeps track of backwards extremities for a room.
// Backwards extremities are the earliest (DAG-wise) known events which we have
// the entire event JSON. These event IDs are used in federation requests to fetch
// even earlier events.
//
// We persist the previous event IDs as well, one per row, so when we do fetch even
// earlier events we can simply delete rows which referenced it. Consider the graph:
// A
// | Event C has 1 prev_event ID: A.
// B C
// |___| Event D has 2 prev_event IDs: B and C.
// |
// D
// The earliest known event we have is D, so this table has 2 rows.
// A backfill request gives us C but not B. We delete rows where prev_event=C. This
// still means that D is a backwards extremity as we do not have event B. However, event
// C is *also* a backwards extremity at this point as we do not have event A. Later,
// when we fetch event B, we delete rows where prev_event=B. This then removes D as
// a backwards extremity because there are no more rows with event_id=B.
type BackwardsExtremities struct {
insertBackwardExtremityStmt *sql.Stmt
selectBackwardExtremitiesForRoomStmt *sql.Stmt
deleteBackwardExtremityStmt *sql.Stmt
}
// NewBackwardsExtremities prepares the table
func NewBackwardsExtremities(db *sql.DB, stmts BackwardsExtremitiesStatements) (table BackwardsExtremities, err error) {
_, err = db.Exec(stmts.Schema())
if err != nil {
return
}
if table.insertBackwardExtremityStmt, err = db.Prepare(stmts.InsertBackwardExtremity()); err != nil {
return
}
if table.selectBackwardExtremitiesForRoomStmt, err = db.Prepare(stmts.SelectBackwardExtremitiesForRoom()); err != nil {
return
}
if table.deleteBackwardExtremityStmt, err = db.Prepare(stmts.DeleteBackwardExtremity()); err != nil {
return
}
return
}
// InsertsBackwardExtremity inserts a new backwards extremity.
func (s *BackwardsExtremities) InsertsBackwardExtremity(
ctx context.Context, txn *sql.Tx, roomID, eventID string, prevEventID string,
) (err error) {
_, err = txn.Stmt(s.insertBackwardExtremityStmt).ExecContext(ctx, roomID, eventID, prevEventID)
return
}
// SelectBackwardExtremitiesForRoom retrieves all backwards extremities for the room.
func (s *BackwardsExtremities) SelectBackwardExtremitiesForRoom(
ctx context.Context, roomID string,
) (eventIDs []string, err error) {
rows, err := s.selectBackwardExtremitiesForRoomStmt.QueryContext(ctx, roomID)
if err != nil {
return
}
defer common.CloseAndLogIfError(ctx, rows, "selectBackwardExtremitiesForRoom: rows.close() failed")
for rows.Next() {
var eID string
if err = rows.Scan(&eID); err != nil {
return
}
eventIDs = append(eventIDs, eID)
}
return eventIDs, rows.Err()
}
// DeleteBackwardExtremity removes a backwards extremity for a room, if one existed.
func (s *BackwardsExtremities) DeleteBackwardExtremity(
ctx context.Context, txn *sql.Tx, roomID, knownEventID string,
) (err error) {
_, err = txn.Stmt(s.deleteBackwardExtremityStmt).ExecContext(ctx, roomID, knownEventID)
return
}