Storage functions for event types

src/github.com/matrix-org/dendrite/roomserver/storage/sql.go

@@ -8,25 +8,38 @@ import (
 type statements struct {
 	selectPartitionOffsetsStmt *sql.Stmt
 	upsertPartitionOffsetStmt  *sql.Stmt
+        insertEventTypeNIDStmt *sql.Stmt
+        selectEventTypeNIDStmt *sql.Stmt
 }
 
 func (s *statements) prepare(db *sql.DB) error {
 	var err error
 
-	_, err = db.Exec(partitionOffsetsSchema)
+        if err = s.preparePartitionOffsets(db); err != nil {
-	if err != nil {
+            return err
-		return err
+        }
-	}
+
+        if err = s.prepareEventTypes(db); err != nil {
+            return err
+        }
 
-	if s.selectPartitionOffsetsStmt, err = db.Prepare(selectPartitionOffsetsSQL); err != nil {
-		return err
-	}
-	if s.upsertPartitionOffsetStmt, err = db.Prepare(upsertPartitionOffsetsSQL); err != nil {
-		return err
-	}
 	return nil
 }
 
+func (s *statements) preparePartitionOffsets(db *sql.DB) (err error) {
+    _, err = db.Exec(partitionOffsetsSchema)
+    if err != nil {
+	    return
+    }
+    if s.selectPartitionOffsetsStmt, err = db.Prepare(selectPartitionOffsetsSQL); err != nil {
+	    return
+    }
+    if s.upsertPartitionOffsetStmt, err = db.Prepare(upsertPartitionOffsetsSQL); err != nil {
+        return
+    }
+    return
+}
+
 const partitionOffsetsSchema = `
 -- The offsets that the server has processed up to.
 CREATE TABLE IF NOT EXISTS partition_offsets (
@@ -68,3 +81,82 @@ func (s *statements) upsertPartitionOffset(topic string, partition int32, offset
 	_, err := s.upsertPartitionOffsetStmt.Exec(topic, partition, offset)
 	return err
 }
+
+func (s *statements) prepareEventTypes(db *sql.DB) (err error) {
+        _, err = db.Exec(eventTypesSchema)
+        if err != nil {
+            return
+        }
+        if s.insertEventTypeNIDStmt, err = db.Prepare(insertEventTypeNIDSQL); err != nil {
+            return
+        }
+        if s.selectEventTypeNIDStmt, err = db.Prepare(selectEventTypeNIDSQL); err != nil {
+            return
+        }
+        return
+    }
+
+const eventTypesSchema = `
+-- Numeric versions of the event "type"s. Event types tend to be taken from a
+-- small common pool. Assigning each a numeric ID should reduce the amount of
+-- data that needs to be stored and fetched from the database.
+-- It also means that many operations can work with int64 arrays rather than
+-- string arrays which may help reduce GC pressure.
+-- Well known event types are pre-assigned numeric IDs:
+--   1 -> m.room.create
+--   2 -> m.room.power_levels
+--   3 -> m.room.join_rules
+--   4 -> m.room.third_party_invite
+--   5 -> m.room.member
+--   6 -> m.room.redaction
+--   7 -> m.room.history_visibility
+-- Picking well-known numeric IDs for the events types that require special
+-- attention during state conflict resolution means that we write that code
+-- using numeric constants.
+-- It also means that the numeric IDs for common event types should be
+-- consistent between different instances which might make ad-hoc debugging
+-- easier.
+CREATE SEQUENCE IF NOT EXISTS event_type_nid_seq START 65536;
+CREATE TABLE IF NOT EXISTS event_types (
+    -- Local numeric ID for the event type.
+    event_type_nid BIGINT PRIMARY KEY DEFAULT nextval('event_type_nid_seq'),
+    -- The string event_type.
+    event_type TEXT NOT NULL CONSTRAINT event_type_unique UNIQUE
+);
+INSERT INTO event_types (event_type_nid, event_type) VALUES (
+    (1, 'm.room.create'),
+    (2, 'm.room.power_levels'),
+    (3, 'm.room.join_rules'),
+    (4, 'm.room.third_party_invite'),
+    (5, 'm.room.member'),
+    (6, 'm.room.redaction'),
+    (7, 'm.room.history_visibility'),
+) ON CONFLICT DO NOTHING;
+`
+
+const insertEventTypeNIDSQL = "" +
+    "INSERT INTO event_types (event_type) VALUES ($1)" +
+    " ON CONFLICT ON CONSTRAINT event_type_unique" +
+    " DO UPDATE SET event_type = $1" +
+    " RETURNING (event_type_nid)"
+
+const selectEventTypeNIDSQL = "" +
+    "SELECT event_type_nid FROM event_types WHERE event_type = $1"
+
+func (s *statements) insertEventTypeNID(eventType string) (eventTypeNID int64, err error) {
+    err = s.insertEventTypeNIDStmt.QueryRow(eventType).Scan(&eventTypeNID)
+    if err == sql.ErrNoRows {
+        eventTypeNID = 0
+        err = nil
+    }
+    return
+}
+
+func (s *statements) selectEventTypeNID(eventType string) (eventTypeNID int64, err error) {
+    err = s.selectEventTypeNIDStmt.QueryRow(eventType).Scan(&eventTypeNID)
+    if err == sql.ErrNoRows {
+        eventTypeNID = 0
+        err = nil
+    }
+    return
+}