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koans.go
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koans.go
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package koans
import (
"context"
"database/sql"
"fmt"
"log"
"net/url"
"os"
"strconv"
"strings"
"testing"
"github.com/mattn/go-sqlite3"
_ "github.com/mattn/go-sqlite3"
"github.com/stretchr/testify/assert"
)
const (
DbPrefix = "file:"
DbName = "koans.db"
BackupDbName = "koans-backup.db"
DbFile = DbPrefix + DbName
DbBackupFile = DbPrefix + BackupDbName
DbFileShm = DbFile + "-shm"
DbFileWal = DbFile + "-wal"
SqliteCmd = "sqlite3"
SqliteSchema = "main"
SqliteConnErr = "failed to open db connection to %s"
)
var DbFiles []string = []string{
DbFile, DbFileShm, DbFileWal, DbBackupFile,
}
type Koans struct {
db *sql.DB
}
func New() (*Koans, error) {
var url string
var db *sql.DB
var err error
if url, err = DbUrl(); err != nil {
log.Printf("failed to construct sqlite url: %v\n", err)
return nil, err
}
if db, err = Setup(url); err != nil {
log.Printf("failed to open sqlite3 conn: %v\n", err)
return nil, err
}
return &Koans{
db: db,
}, nil
}
// DbUrl - construct a Sqlite DSN (Data Source Name) string
// https://github.com/mattn/go-sqlite3#connection-string
func DbUrl() (string, error) {
var dataSourceName *url.URL
var err error
if dataSourceName, err = url.Parse(DbFile); err != nil {
return "", err
}
pragmas := url.Values{}
// mattn/go-sqlite3 DSN keys
// not every PRAGMA has a DSN equivalent
pragmas.Set("_busy_timeout", strconv.Itoa(PragmaTimeoutMs))
pragmas.Set("_foreign_keys", strconv.FormatBool(true))
pragmas.Set("_journal_mode", JournalModeWAL)
pragmas.Set("_synchronous", PragmaSynchronousNormal)
dataSourceName.RawQuery = pragmas.Encode()
log.Println(dataSourceName.String())
return dataSourceName.String(), err
}
// BackupDBUrl - construct a Sqlite DSN (Data Source Name) string as a backup target
// https://www.sqlite.org/backup.html
func BackupDbUrl() (string, error) {
var dataSourceName *url.URL
var err error
if dataSourceName, err = url.Parse(DbBackupFile); err != nil {
return "", err
}
pragmas := url.Values{}
// mattn/go-sqlite3 DSN keys
// not every PRAGMA has a DSN equivalent
pragmas.Set("_busy_timeout", strconv.Itoa(PragmaTimeoutMs))
pragmas.Set("_foreign_keys", strconv.FormatBool(true))
pragmas.Set("_journal_mode", JournalModeDelete)
pragmas.Set("_synchronous", PragmaSynchronousFull)
dataSourceName.RawQuery = pragmas.Encode()
log.Println(dataSourceName.String())
return dataSourceName.String(), err
}
func Setup(dbUrl string) (*sql.DB, error) {
var db *sql.DB
var err error
if db, err = sql.Open(SqliteCmd, dbUrl); err != nil {
return nil, err
}
if _, err = db.Exec(CreateStrictTableStmt); err != nil {
log.Printf("%q: %s\n", err, CreateStrictTableStmt)
return db, err
}
if _, err = db.Exec(CreateStrictWithoutRowIdTableStmt); err != nil {
log.Printf("%q: %s\n", err, CreateStrictWithoutRowIdTableStmt)
return db, err
}
return db, err
}
func Teardown(t *testing.T) error {
var err error
for i := range DbFiles {
file := DbFiles[i]
err = os.Remove(strings.Replace(file, DbPrefix, "", 1))
if t != nil {
assert.Nil(t, err)
}
}
return err
}
// Backup - backup WAL mode SQLite DB
// https://github.com/mattn/go-sqlite3/blob/master/_example/hook/hook.go
func (k *Koans) Backup() error {
src, err := k.db.Conn(context.Background())
if err != nil {
return err
}
backupDbUrl, err := BackupDbUrl()
if err != nil {
return err
}
var backupDb *sql.DB
backupDb, err = sql.Open(SqliteCmd, backupDbUrl)
if err != nil {
return err
}
target, err := backupDb.Conn(context.Background())
if err != nil {
return err
}
return target.Raw(func(destConn any) error {
return src.Raw(func(srcConn any) error {
var srcDriver *sqlite3.SQLiteConn
var destDriver *sqlite3.SQLiteConn
var backup *sqlite3.SQLiteBackup
var ok bool
var err error
if destDriver, ok = destConn.(*sqlite3.SQLiteConn); !ok {
return fmt.Errorf(SqliteConnErr, DbBackupFile)
}
if srcDriver, ok = srcConn.(*sqlite3.SQLiteConn); !ok {
return fmt.Errorf(SqliteConnErr, DbFile)
}
if backup, err = destDriver.Backup(SqliteSchema, srcDriver, SqliteSchema); err != nil {
return err
}
if _, err = backup.Step(-1); err != nil {
return err
}
return backup.Finish()
})
})
}