124 lines
4.3 KiB
Go
124 lines
4.3 KiB
Go
// Copyright 2018 New Vector Ltd
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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package sqlite3
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import (
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"context"
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"database/sql"
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"github.com/matrix-org/dendrite/common"
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)
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// The purpose of this table is to keep track of backwards extremities for a room.
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// Backwards extremities are the earliest (DAG-wise) known events which we have
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// the entire event JSON. These event IDs are used in federation requests to fetch
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// even earlier events.
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//
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// We persist the previous event IDs as well, one per row, so when we do fetch even
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// earlier events we can simply delete rows which referenced it. Consider the graph:
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// A
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// | Event C has 1 prev_event ID: A.
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// B C
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// |___| Event D has 2 prev_event IDs: B and C.
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// |
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// D
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// The earliest known event we have is D, so this table has 2 rows.
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// A backfill request gives us C but not B. We delete rows where prev_event=C. This
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// still means that D is a backwards extremity as we do not have event B. However, event
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// C is *also* a backwards extremity at this point as we do not have event A. Later,
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// when we fetch event B, we delete rows where prev_event=B. This then removes D as
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// a backwards extremity because there are no more rows with event_id=B.
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const backwardExtremitiesSchema = `
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-- Stores output room events received from the roomserver.
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CREATE TABLE IF NOT EXISTS syncapi_backward_extremities (
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-- The 'room_id' key for the event.
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room_id TEXT NOT NULL,
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-- The event ID for the last known event. This is the backwards extremity.
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event_id TEXT NOT NULL,
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-- The prev_events for the last known event. This is used to update extremities.
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prev_event_id TEXT NOT NULL,
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PRIMARY KEY(room_id, event_id, prev_event_id)
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);
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`
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const insertBackwardExtremitySQL = "" +
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"INSERT INTO syncapi_backward_extremities (room_id, event_id, prev_event_id)" +
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" VALUES ($1, $2, $3)" +
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" ON CONFLICT (room_id, event_id, prev_event_id) DO NOTHING"
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const selectBackwardExtremitiesForRoomSQL = "" +
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"SELECT DISTINCT event_id FROM syncapi_backward_extremities WHERE room_id = $1"
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const deleteBackwardExtremitySQL = "" +
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"DELETE FROM syncapi_backward_extremities WHERE room_id = $1 AND prev_event_id = $2"
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type backwardExtremitiesStatements struct {
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insertBackwardExtremityStmt *sql.Stmt
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selectBackwardExtremitiesForRoomStmt *sql.Stmt
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deleteBackwardExtremityStmt *sql.Stmt
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}
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func (s *backwardExtremitiesStatements) prepare(db *sql.DB) (err error) {
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_, err = db.Exec(backwardExtremitiesSchema)
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if err != nil {
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return
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}
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if s.insertBackwardExtremityStmt, err = db.Prepare(insertBackwardExtremitySQL); err != nil {
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return
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}
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if s.selectBackwardExtremitiesForRoomStmt, err = db.Prepare(selectBackwardExtremitiesForRoomSQL); err != nil {
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return
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}
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if s.deleteBackwardExtremityStmt, err = db.Prepare(deleteBackwardExtremitySQL); err != nil {
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return
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}
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return
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}
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func (s *backwardExtremitiesStatements) insertsBackwardExtremity(
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ctx context.Context, txn *sql.Tx, roomID, eventID string, prevEventID string,
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) (err error) {
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_, err = txn.Stmt(s.insertBackwardExtremityStmt).ExecContext(ctx, roomID, eventID, prevEventID)
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return
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}
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func (s *backwardExtremitiesStatements) selectBackwardExtremitiesForRoom(
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ctx context.Context, roomID string,
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) (eventIDs []string, err error) {
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rows, err := s.selectBackwardExtremitiesForRoomStmt.QueryContext(ctx, roomID)
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if err != nil {
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return
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}
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defer common.CloseAndLogIfError(ctx, rows, "selectBackwardExtremitiesForRoom: rows.close() failed")
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for rows.Next() {
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var eID string
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if err = rows.Scan(&eID); err != nil {
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return
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}
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eventIDs = append(eventIDs, eID)
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}
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return eventIDs, rows.Err()
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}
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func (s *backwardExtremitiesStatements) deleteBackwardExtremity(
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ctx context.Context, txn *sql.Tx, roomID, knownEventID string,
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) (err error) {
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_, err = txn.Stmt(s.deleteBackwardExtremityStmt).ExecContext(ctx, roomID, knownEventID)
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return
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}
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