dendrite/syncapi/storage/postgres/output_room_events_topology_table.go
Kiril Vladimiroff d5dbe546e4
Always defer *sql.Rows.Close and consult with Err (#844)
* Always defer *sql.Rows.Close and consult with Err

database/sql.Rows.Next() makes sure to call Close only after exhausting
result rows which would NOT happen when returning early from a bad Scan.
Close being idempotent makes it a great candidate to get always deferred
regardless of what happens later on the result set.

This change also makes sure call Err() after exhausting Next() and
propagate non-nil results from it as the documentation advises.

Closes #764

Signed-off-by: Kiril Vladimiroff <kiril@vladimiroff.org>

* Override named result parameters in last returns

Signed-off-by: Kiril Vladimiroff <kiril@vladimiroff.org>

* Do the same over new changes that got merged

Signed-off-by: Kiril Vladimiroff <kiril@vladimiroff.org>

Co-authored-by: Neil Alexander <neilalexander@users.noreply.github.com>
2020-02-11 14:12:21 +00:00

191 lines
6.4 KiB
Go

// Copyright 2018 New Vector Ltd
//
// 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 postgres
import (
"context"
"database/sql"
"github.com/matrix-org/dendrite/syncapi/types"
"github.com/matrix-org/gomatrixserverlib"
)
const outputRoomEventsTopologySchema = `
-- Stores output room events received from the roomserver.
CREATE TABLE IF NOT EXISTS syncapi_output_room_events_topology (
-- The event ID for the event.
event_id TEXT PRIMARY KEY,
-- The place of the event in the room's topology. This can usually be determined
-- from the event's depth.
topological_position BIGINT NOT NULL,
-- The 'room_id' key for the event.
room_id TEXT NOT NULL
);
-- The topological order will be used in events selection and ordering
CREATE UNIQUE INDEX IF NOT EXISTS syncapi_event_topological_position_idx ON syncapi_output_room_events_topology(topological_position, room_id);
`
const insertEventInTopologySQL = "" +
"INSERT INTO syncapi_output_room_events_topology (event_id, topological_position, room_id)" +
" VALUES ($1, $2, $3)" +
" ON CONFLICT (topological_position, room_id) DO UPDATE SET event_id = $1"
const selectEventIDsInRangeASCSQL = "" +
"SELECT event_id FROM syncapi_output_room_events_topology" +
" WHERE room_id = $1 AND topological_position > $2 AND topological_position <= $3" +
" ORDER BY topological_position ASC LIMIT $4"
const selectEventIDsInRangeDESCSQL = "" +
"SELECT event_id FROM syncapi_output_room_events_topology" +
" WHERE room_id = $1 AND topological_position > $2 AND topological_position <= $3" +
" ORDER BY topological_position DESC LIMIT $4"
const selectPositionInTopologySQL = "" +
"SELECT topological_position FROM syncapi_output_room_events_topology" +
" WHERE event_id = $1"
const selectMaxPositionInTopologySQL = "" +
"SELECT MAX(topological_position) FROM syncapi_output_room_events_topology" +
" WHERE room_id = $1"
const selectEventIDsFromPositionSQL = "" +
"SELECT event_id FROM syncapi_output_room_events_topology" +
" WHERE room_id = $1 AND topological_position = $2"
type outputRoomEventsTopologyStatements struct {
insertEventInTopologyStmt *sql.Stmt
selectEventIDsInRangeASCStmt *sql.Stmt
selectEventIDsInRangeDESCStmt *sql.Stmt
selectPositionInTopologyStmt *sql.Stmt
selectMaxPositionInTopologyStmt *sql.Stmt
selectEventIDsFromPositionStmt *sql.Stmt
}
func (s *outputRoomEventsTopologyStatements) prepare(db *sql.DB) (err error) {
_, err = db.Exec(outputRoomEventsTopologySchema)
if err != nil {
return
}
if s.insertEventInTopologyStmt, err = db.Prepare(insertEventInTopologySQL); err != nil {
return
}
if s.selectEventIDsInRangeASCStmt, err = db.Prepare(selectEventIDsInRangeASCSQL); err != nil {
return
}
if s.selectEventIDsInRangeDESCStmt, err = db.Prepare(selectEventIDsInRangeDESCSQL); err != nil {
return
}
if s.selectPositionInTopologyStmt, err = db.Prepare(selectPositionInTopologySQL); err != nil {
return
}
if s.selectMaxPositionInTopologyStmt, err = db.Prepare(selectMaxPositionInTopologySQL); err != nil {
return
}
if s.selectEventIDsFromPositionStmt, err = db.Prepare(selectEventIDsFromPositionSQL); err != nil {
return
}
return
}
// insertEventInTopology inserts the given event in the room's topology, based
// on the event's depth.
func (s *outputRoomEventsTopologyStatements) insertEventInTopology(
ctx context.Context, event *gomatrixserverlib.Event,
) (err error) {
_, err = s.insertEventInTopologyStmt.ExecContext(
ctx, event.EventID(), event.Depth(), event.RoomID(),
)
return
}
// selectEventIDsInRange selects the IDs of events which positions are within a
// given range in a given room's topological order.
// Returns an empty slice if no events match the given range.
func (s *outputRoomEventsTopologyStatements) selectEventIDsInRange(
ctx context.Context, roomID string, fromPos, toPos types.StreamPosition,
limit int, chronologicalOrder bool,
) (eventIDs []string, err error) {
// Decide on the selection's order according to whether chronological order
// is requested or not.
var stmt *sql.Stmt
if chronologicalOrder {
stmt = s.selectEventIDsInRangeASCStmt
} else {
stmt = s.selectEventIDsInRangeDESCStmt
}
// Query the event IDs.
rows, err := stmt.QueryContext(ctx, roomID, fromPos, toPos, limit)
if err == sql.ErrNoRows {
// If no event matched the request, return an empty slice.
return []string{}, nil
} else if err != nil {
return
}
defer rows.Close() // nolint: errcheck
// Return the IDs.
var eventID string
for rows.Next() {
if err = rows.Scan(&eventID); err != nil {
return
}
eventIDs = append(eventIDs, eventID)
}
return eventIDs, rows.Err()
}
// selectPositionInTopology returns the position of a given event in the
// topology of the room it belongs to.
func (s *outputRoomEventsTopologyStatements) selectPositionInTopology(
ctx context.Context, eventID string,
) (pos types.StreamPosition, err error) {
err = s.selectPositionInTopologyStmt.QueryRowContext(ctx, eventID).Scan(&pos)
return
}
func (s *outputRoomEventsTopologyStatements) selectMaxPositionInTopology(
ctx context.Context, roomID string,
) (pos types.StreamPosition, err error) {
err = s.selectMaxPositionInTopologyStmt.QueryRowContext(ctx, roomID).Scan(&pos)
return
}
// selectEventIDsFromPosition returns the IDs of all events that have a given
// position in the topology of a given room.
func (s *outputRoomEventsTopologyStatements) selectEventIDsFromPosition(
ctx context.Context, roomID string, pos types.StreamPosition,
) (eventIDs []string, err error) {
// Query the event IDs.
rows, err := s.selectEventIDsFromPositionStmt.QueryContext(ctx, roomID, pos)
if err == sql.ErrNoRows {
// If no event matched the request, return an empty slice.
return []string{}, nil
} else if err != nil {
return
}
defer rows.Close() // nolint: errcheck
// Return the IDs.
var eventID string
for rows.Next() {
if err = rows.Scan(&eventID); err != nil {
return
}
eventIDs = append(eventIDs, eventID)
}
return eventIDs, rows.Err()
}