// Query implements DB.QueryNoCache. It *always* hits the database and updates the cache.
func (c *Cache) QueryNoCache(query string) (*data.Frame, error) {
name := tableName(query)
c.logf("caching [%s] %.200s", name, query)
if err := c.saveQuery(query); err != nil {
c.purgeQuery(name)
return nil, err
}
return data.ReadFromDB(c.cache, "SELECT * FROM "+name)
}
// staleQueries returns all queries that haven't being accessed in the lastAccessed seconds.
func staleQueries(db *sql.DB, lastAccessed int) (*data.Frame, error) {
const stale = `
SELECT DISTINCT
table_name
FROM
(SELECT table_name, MAX(time) as last_access FROM log GROUP BY table_name) a
WHERE
last_access <= datetime('now', '-%d seconds')`
return data.ReadFromDB(db, fmt.Sprintf(stale, lastAccessed))
}
// Query runs a query and returns a DataFrame
func (s *SQL) Query(query string) (*data.Frame, error) {
df, err := data.ReadFromDB(s.db, query)
if err != nil {
return nil, err
}
if s.driver == "mysql" {
df.ConvertTime()
df.ConvertNumeric()
}
return df, nil
}
// outdatedQueries returns all queries that were not updated in the lastUpdated seconds.
func outdatedQueries(db *sql.DB, lastUpdated int) (*data.Frame, error) {
const outdated = `
SELECT
q.table_name, q.sql
FROM
queries q
LEFT JOIN
(SELECT table_name, MAX(time) AS last_updated FROM log WHERE duration != -1 GROUP BY table_name) u
ON q.table_name = u.table_name
WHERE
last_updated IS NULL OR last_updated <= datetime('now', '-%d seconds')`
return data.ReadFromDB(db, fmt.Sprintf(outdated, lastUpdated))
}
// Query implements DB.Query. If query was cached before, this result is returned; otherwise
// underlying DB is queried and the result is stored in the cache first.
func (c *Cache) Query(query string) (*data.Frame, error) {
name := tableName(query)
if cacheExists(c.cache, name) {
c.logf("cache hit for [%s] %.200s", name, query)
// Cache access that doesn't hit the underlying DB is logged with negative duration.
c.lock.Lock()
defer c.lock.Unlock()
if err := logCacheAccess(c.cache, name, time.Now(), time.Duration(-1)); err != nil {
return nil, err
}
return data.ReadFromDB(c.cache, "SELECT * FROM "+name)
}
return c.QueryNoCache(query)
}