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sqlhandler.go
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sqlhandler.go
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// Copyright (C) 2016-2018 vLife Systems Ltd <http://vlifesystems.com>
// Licensed under an MIT licence. Please see LICENSE.md for details.
// +build !nosqlite3
package experiment
import (
"database/sql"
"errors"
"fmt"
"os"
"sync"
_ "github.com/denisenkom/go-mssqldb"
_ "github.com/go-sql-driver/mysql"
_ "github.com/lib/pq"
_ "github.com/mattn/go-sqlite3"
)
var errDatabaseNotOpen = errors.New("connection to database not open")
type sqlHandler struct {
driverName string
dataSourceName string
query string
db *sql.DB
openConn int
sync.Mutex
}
func newSQLHandler(
driverName string,
dataSourceName string,
query string,
) (*sqlHandler, error) {
validSQLDriverNames := []string{"sqlite3", "mysql", "mssql", "postgres"}
for _, name := range validSQLDriverNames {
if name == driverName {
return &sqlHandler{
driverName: driverName,
dataSourceName: dataSourceName,
query: query,
db: nil,
openConn: 0,
}, nil
}
}
return nil, fmt.Errorf("invalid driverName: %s", driverName)
}
func (s *sqlHandler) Open() error {
s.Lock()
defer s.Unlock()
if s.openConn == 0 {
if s.driverName == "sqlite3" && !fileExists(s.dataSourceName) {
return fmt.Errorf("database doesn't exist: %s", s.dataSourceName)
}
db, err := sql.Open(s.driverName, s.dataSourceName)
s.db = db
if err != nil {
return err
}
}
s.openConn++
return nil
}
func (s *sqlHandler) Close() error {
s.Lock()
defer s.Unlock()
if s.openConn >= 1 {
s.openConn--
if s.openConn == 0 {
return s.db.Close()
}
}
return nil
}
func (s *sqlHandler) Rows() (*sql.Rows, error) {
s.Lock()
if s.openConn < 1 {
s.Unlock()
return nil, errDatabaseNotOpen
}
s.Unlock()
rows, err := s.db.Query(s.query)
if err != nil {
s.Close()
}
return rows, err
}
func fileExists(path string) bool {
fi, err := os.Stat(path)
if err != nil {
return false
}
return fi.Mode().IsRegular()
}