diff options
Diffstat (limited to 'roomserver/storage/postgres/previous_events_table.go')
| -rw-r--r-- | roomserver/storage/postgres/previous_events_table.go | 100 |
1 files changed, 100 insertions, 0 deletions
diff --git a/roomserver/storage/postgres/previous_events_table.go b/roomserver/storage/postgres/previous_events_table.go new file mode 100644 index 00000000..4c21b308 --- /dev/null +++ b/roomserver/storage/postgres/previous_events_table.go @@ -0,0 +1,100 @@ +// Copyright 2017-2018 New Vector Ltd +// Copyright 2019-2020 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 postgres + +import ( + "context" + "database/sql" + + "github.com/matrix-org/dendrite/common" + "github.com/matrix-org/dendrite/roomserver/types" +) + +const previousEventSchema = ` +-- The previous events table stores the event_ids referenced by the events +-- stored in the events table. +-- This is used to tell if a new event is already referenced by an event in +-- the database. +CREATE TABLE IF NOT EXISTS roomserver_previous_events ( + -- The string event ID taken from the prev_events key of an event. + previous_event_id TEXT NOT NULL, + -- The SHA256 reference hash taken from the prev_events key of an event. + previous_reference_sha256 BYTEA NOT NULL, + -- A list of numeric event IDs of events that reference this prev_event. + event_nids BIGINT[] NOT NULL, + CONSTRAINT roomserver_previous_event_id_unique UNIQUE (previous_event_id, previous_reference_sha256) +); +` + +// Insert an entry into the previous_events table. +// If there is already an entry indicating that an event references that previous event then +// add the event NID to the list to indicate that this event references that previous event as well. +// This should only be modified while holding a "FOR UPDATE" lock on the row in the rooms table for this room. +// The lock is necessary to avoid data races when checking whether an event is already referenced by another event. +const insertPreviousEventSQL = "" + + "INSERT INTO roomserver_previous_events" + + " (previous_event_id, previous_reference_sha256, event_nids)" + + " VALUES ($1, $2, array_append('{}'::bigint[], $3))" + + " ON CONFLICT ON CONSTRAINT roomserver_previous_event_id_unique" + + " DO UPDATE SET event_nids = array_append(roomserver_previous_events.event_nids, $3)" + + " WHERE $3 != ALL(roomserver_previous_events.event_nids)" + +// Check if the event is referenced by another event in the table. +// This should only be done while holding a "FOR UPDATE" lock on the row in the rooms table for this room. +const selectPreviousEventExistsSQL = "" + + "SELECT 1 FROM roomserver_previous_events" + + " WHERE previous_event_id = $1 AND previous_reference_sha256 = $2" + +type previousEventStatements struct { + insertPreviousEventStmt *sql.Stmt + selectPreviousEventExistsStmt *sql.Stmt +} + +func (s *previousEventStatements) prepare(db *sql.DB) (err error) { + _, err = db.Exec(previousEventSchema) + if err != nil { + return + } + + return statementList{ + {&s.insertPreviousEventStmt, insertPreviousEventSQL}, + {&s.selectPreviousEventExistsStmt, selectPreviousEventExistsSQL}, + }.prepare(db) +} + +func (s *previousEventStatements) insertPreviousEvent( + ctx context.Context, + txn *sql.Tx, + previousEventID string, + previousEventReferenceSHA256 []byte, + eventNID types.EventNID, +) error { + stmt := common.TxStmt(txn, s.insertPreviousEventStmt) + _, err := stmt.ExecContext( + ctx, previousEventID, previousEventReferenceSHA256, int64(eventNID), + ) + return err +} + +// Check if the event reference exists +// Returns sql.ErrNoRows if the event reference doesn't exist. +func (s *previousEventStatements) selectPreviousEventExists( + ctx context.Context, txn *sql.Tx, eventID string, eventReferenceSHA256 []byte, +) error { + var ok int64 + stmt := common.TxStmt(txn, s.selectPreviousEventExistsStmt) + return stmt.QueryRowContext(ctx, eventID, eventReferenceSHA256).Scan(&ok) +} |