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// Copyright (c) 2018 David Crawshaw <david@zentus.com>
//
// Permission to use, copy, modify, and distribute this software for any
// purpose with or without fee is hereby granted, provided that the above
// copyright notice and this permission notice appear in all copies.
//
// THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
// WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
// MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
// ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
// WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
// ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
// OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
package sqlitex
import (
"fmt"
"runtime"
"strings"
"github.com/go-llsqlite/crawshaw"
)
// Save creates a named SQLite transaction using SAVEPOINT.
//
// On success Savepoint returns a releaseFn that will call either
// RELEASE or ROLLBACK depending on whether the parameter *error
// points to a nil or non-nil error. This is designed to be deferred.
//
// Example:
//
// func doWork(conn *sqlite.Conn) (err error) {
// defer sqlitex.Save(conn)(&err)
//
// // ... do work in the transaction
// }
//
// https://www.sqlite.org/lang_savepoint.html
func Save(conn *sqlite.Conn) (releaseFn func(*error)) {
name := "sqlitex.Save" // safe as names can be reused
var pc [3]uintptr
if n := runtime.Callers(0, pc[:]); n > 0 {
frames := runtime.CallersFrames(pc[:n])
if _, more := frames.Next(); more { // runtime.Callers
if _, more := frames.Next(); more { // savepoint.Save
frame, _ := frames.Next() // caller we care about
if frame.Function != "" {
name = frame.Function
}
}
}
}
releaseFn, err := savepoint(conn, name)
if err != nil {
if sqlite.ErrCode(err) == sqlite.SQLITE_INTERRUPT {
return func(errp *error) {
if *errp == nil {
*errp = err
}
}
}
panic(err)
}
return releaseFn
}
func savepoint(conn *sqlite.Conn, name string) (releaseFn func(*error), err error) {
if strings.Contains(name, `"`) {
return nil, fmt.Errorf("sqlitex.Savepoint: invalid name: %q", name)
}
if err := Exec(conn, fmt.Sprintf("SAVEPOINT %q;", name), nil); err != nil {
return nil, err
}
tracer := conn.Tracer()
if tracer != nil {
tracer.Push("TX " + name)
}
releaseFn = func(errp *error) {
if tracer != nil {
tracer.Pop()
}
recoverP := recover()
// If a query was interrupted or if a user exec'd COMMIT or
// ROLLBACK, then everything was already rolled back
// automatically, thus returning the connection to autocommit
// mode.
if conn.GetAutocommit() {
// There is nothing to rollback.
if recoverP != nil {
panic(recoverP)
}
return
}
if *errp == nil && recoverP == nil {
// Success path. Release the savepoint successfully.
*errp = Exec(conn, fmt.Sprintf("RELEASE %q;", name), nil)
if *errp == nil {
return
}
// Possible interrupt. Fall through to the error path.
if conn.GetAutocommit() {
// There is nothing to rollback.
if recoverP != nil {
panic(recoverP)
}
return
}
}
orig := ""
if *errp != nil {
orig = (*errp).Error() + "\n\t"
}
// Error path.
// Always run ROLLBACK even if the connection has been interrupted.
oldDoneCh := conn.SetInterrupt(nil)
defer conn.SetInterrupt(oldDoneCh)
err := Exec(conn, fmt.Sprintf("ROLLBACK TO %q;", name), nil)
if err != nil {
panic(orig + err.Error())
}
err = Exec(conn, fmt.Sprintf("RELEASE %q;", name), nil)
if err != nil {
panic(orig + err.Error())
}
if recoverP != nil {
panic(recoverP)
}
}
return releaseFn, nil
}
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