2017-02-15 14:43:19 +00:00
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package storage
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import (
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"database/sql"
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"github.com/matrix-org/dendrite/roomserver/types"
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)
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const eventTypesSchema = `
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-- Numeric versions of the event "type"s. Event types tend to be taken from a
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-- small common pool. Assigning each a numeric ID should reduce the amount of
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-- data that needs to be stored and fetched from the database.
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-- It also means that many operations can work with int64 arrays rather than
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-- string arrays which may help reduce GC pressure.
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-- Well known event types are pre-assigned numeric IDs:
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-- 1 -> m.room.create
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-- 2 -> m.room.power_levels
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-- 3 -> m.room.join_rules
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-- 4 -> m.room.third_party_invite
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-- 5 -> m.room.member
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-- 6 -> m.room.redaction
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-- 7 -> m.room.history_visibility
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-- Picking well-known numeric IDs for the events types that require special
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-- attention during state conflict resolution means that we write that code
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-- using numeric constants.
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-- It also means that the numeric IDs for common event types should be
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-- consistent between different instances which might make ad-hoc debugging
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-- easier.
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-- Other event types are automatically assigned numeric IDs starting from 2**16.
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-- This leaves room to add more pre-assigned numeric IDs and clearly separates
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-- the automatically assigned IDs from the pre-assigned IDs.
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CREATE SEQUENCE IF NOT EXISTS event_type_nid_seq START 65536;
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CREATE TABLE IF NOT EXISTS event_types (
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-- Local numeric ID for the event type.
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event_type_nid BIGINT PRIMARY KEY DEFAULT nextval('event_type_nid_seq'),
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-- The string event_type.
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event_type TEXT NOT NULL CONSTRAINT event_type_unique UNIQUE
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);
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INSERT INTO event_types (event_type_nid, event_type) VALUES
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(1, 'm.room.create'),
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(2, 'm.room.power_levels'),
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(3, 'm.room.join_rules'),
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(4, 'm.room.third_party_invite'),
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(5, 'm.room.member'),
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(6, 'm.room.redaction'),
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(7, 'm.room.history_visibility') ON CONFLICT DO NOTHING;
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`
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// Assign a new numeric event type ID.
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// The usual case is that the event type is not in the database.
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// In that case the ID will be assigned using the next value from the sequence.
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// We use `RETURNING` to tell postgres to return the assigned ID.
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// But it's possible that the type was added in a query that raced with us.
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2017-02-22 16:51:10 +00:00
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// This will result in a conflict on the event_type_unique constraint, in this
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// case we do nothing. Postgresql won't return a row in that case so we rely on
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// the caller catching the sql.ErrNoRows error and running a select to get the row.
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// We could get postgresql to return the row on a conflict by updating the row
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// but it doesn't seem like a good idea to modify the rows just to make postgresql
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// return it. Modifying the rows will cause postgres to assign a new tuple for the
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// row even though the data doesn't change resulting in unncesssary modifications
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// to the indexes.
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2017-02-15 14:43:19 +00:00
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const insertEventTypeNIDSQL = "" +
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"INSERT INTO event_types (event_type) VALUES ($1)" +
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" ON CONFLICT ON CONSTRAINT event_type_unique" +
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2017-02-22 16:51:10 +00:00
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" DO NOTHING RETURNING (event_type_nid)"
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2017-02-15 14:43:19 +00:00
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const selectEventTypeNIDSQL = "" +
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"SELECT event_type_nid FROM event_types WHERE event_type = $1"
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type eventTypeStatements struct {
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insertEventTypeNIDStmt *sql.Stmt
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selectEventTypeNIDStmt *sql.Stmt
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}
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func (s *eventTypeStatements) prepare(db *sql.DB) (err error) {
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_, err = db.Exec(eventTypesSchema)
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if err != nil {
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return
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}
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if s.insertEventTypeNIDStmt, err = db.Prepare(insertEventTypeNIDSQL); err != nil {
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return
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}
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if s.selectEventTypeNIDStmt, err = db.Prepare(selectEventTypeNIDSQL); 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 *eventTypeStatements) insertEventTypeNID(eventType string) (types.EventTypeNID, error) {
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var eventTypeNID int64
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err := s.insertEventTypeNIDStmt.QueryRow(eventType).Scan(&eventTypeNID)
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return types.EventTypeNID(eventTypeNID), err
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}
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func (s *eventTypeStatements) selectEventTypeNID(eventType string) (types.EventTypeNID, error) {
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var eventTypeNID int64
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err := s.selectEventTypeNIDStmt.QueryRow(eventType).Scan(&eventTypeNID)
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return types.EventTypeNID(eventTypeNID), err
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}
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