package server import ( "database/sql" "errors" "fmt" _ "github.com/mattn/go-sqlite3" // SQLite driver "log" "strings" "time" ) // Messages cache const ( createMessagesTableQuery = ` BEGIN; CREATE TABLE IF NOT EXISTS messages ( id VARCHAR(20) PRIMARY KEY, time INT NOT NULL, topic VARCHAR(64) NOT NULL, message VARCHAR(512) NOT NULL, title VARCHAR(256) NOT NULL, priority INT NOT NULL, tags VARCHAR(256) NOT NULL ); CREATE INDEX IF NOT EXISTS idx_topic ON messages (topic); COMMIT; ` insertMessageQuery = `INSERT INTO messages (id, time, topic, message, title, priority, tags) VALUES (?, ?, ?, ?, ?, ?, ?)` pruneMessagesQuery = `DELETE FROM messages WHERE time < ?` selectMessagesSinceTimeQuery = ` SELECT id, time, message, title, priority, tags FROM messages WHERE topic = ? AND time >= ? ORDER BY time ASC ` selectMessagesCountQuery = `SELECT COUNT(*) FROM messages` selectMessageCountForTopicQuery = `SELECT COUNT(*) FROM messages WHERE topic = ?` selectTopicsQuery = `SELECT topic FROM messages GROUP BY topic` ) // Schema management queries const ( currentSchemaVersion = 1 createSchemaVersionTableQuery = ` CREATE TABLE IF NOT EXISTS schemaVersion ( id INT PRIMARY KEY, version INT NOT NULL ); ` insertSchemaVersion = `INSERT INTO schemaVersion VALUES (1, ?)` selectSchemaVersionQuery = `SELECT version FROM schemaVersion WHERE id = 1` // 0 -> 1 migrate0To1AlterMessagesTableQuery = ` BEGIN; ALTER TABLE messages ADD COLUMN title VARCHAR(256) NOT NULL DEFAULT(''); ALTER TABLE messages ADD COLUMN priority INT NOT NULL DEFAULT(0); ALTER TABLE messages ADD COLUMN tags VARCHAR(256) NOT NULL DEFAULT(''); COMMIT; ` ) type sqliteCache struct { db *sql.DB } var _ cache = (*sqliteCache)(nil) func newSqliteCache(filename string) (*sqliteCache, error) { db, err := sql.Open("sqlite3", filename) if err != nil { return nil, err } if err := setupDB(db); err != nil { return nil, err } return &sqliteCache{ db: db, }, nil } func (c *sqliteCache) AddMessage(m *message) error { if m.Event != messageEvent { return errUnexpectedMessageType } _, err := c.db.Exec(insertMessageQuery, m.ID, m.Time, m.Topic, m.Message, m.Title, m.Priority, strings.Join(m.Tags, ",")) return err } func (c *sqliteCache) Messages(topic string, since sinceTime) ([]*message, error) { if since.IsNone() { return make([]*message, 0), nil } rows, err := c.db.Query(selectMessagesSinceTimeQuery, topic, since.Time().Unix()) if err != nil { return nil, err } defer rows.Close() messages := make([]*message, 0) for rows.Next() { var timestamp int64 var priority int var id, msg, title, tagsStr string if err := rows.Scan(&id, ×tamp, &msg, &title, &priority, &tagsStr); err != nil { return nil, err } var tags []string if tagsStr != "" { tags = strings.Split(tagsStr, ",") } messages = append(messages, &message{ ID: id, Time: timestamp, Event: messageEvent, Topic: topic, Message: msg, Title: title, Priority: priority, Tags: tags, }) } if err := rows.Err(); err != nil { return nil, err } return messages, nil } func (c *sqliteCache) MessageCount(topic string) (int, error) { rows, err := c.db.Query(selectMessageCountForTopicQuery, topic) if err != nil { return 0, err } defer rows.Close() var count int if !rows.Next() { return 0, errors.New("no rows found") } if err := rows.Scan(&count); err != nil { return 0, err } else if err := rows.Err(); err != nil { return 0, err } return count, nil } func (c *sqliteCache) Topics() (map[string]*topic, error) { rows, err := c.db.Query(selectTopicsQuery) if err != nil { return nil, err } defer rows.Close() topics := make(map[string]*topic) for rows.Next() { var id string if err := rows.Scan(&id); err != nil { return nil, err } topics[id] = newTopic(id) } if err := rows.Err(); err != nil { return nil, err } return topics, nil } func (c *sqliteCache) Prune(olderThan time.Time) error { _, err := c.db.Exec(pruneMessagesQuery, olderThan.Unix()) return err } func setupDB(db *sql.DB) error { // If 'messages' table does not exist, this must be a new database rowsMC, err := db.Query(selectMessagesCountQuery) if err != nil { return setupNewDB(db) } defer rowsMC.Close() // If 'messages' table exists, check 'schemaVersion' table schemaVersion := 0 rowsSV, err := db.Query(selectSchemaVersionQuery) if err == nil { defer rowsSV.Close() if !rowsSV.Next() { return errors.New("cannot determine schema version: cache file may be corrupt") } if err := rowsSV.Scan(&schemaVersion); err != nil { return err } } // Do migrations if schemaVersion == currentSchemaVersion { return nil } else if schemaVersion == 0 { return migrateFrom0To1(db) } return fmt.Errorf("unexpected schema version found: %d", schemaVersion) } func setupNewDB(db *sql.DB) error { if _, err := db.Exec(createMessagesTableQuery); err != nil { return err } if _, err := db.Exec(createSchemaVersionTableQuery); err != nil { return err } if _, err := db.Exec(insertSchemaVersion, currentSchemaVersion); err != nil { return err } return nil } func migrateFrom0To1(db *sql.DB) error { log.Print("Migrating cache database schema: from 0 to 1") if _, err := db.Exec(migrate0To1AlterMessagesTableQuery); err != nil { return err } if _, err := db.Exec(createSchemaVersionTableQuery); err != nil { return err } if _, err := db.Exec(insertSchemaVersion, 1); err != nil { return err } return nil }