Alerting: fix postgres migration on conflict (#35556)

pkg/services/sqlstore/migrations/ualert/ualert.go

@@ -4,6 +4,7 @@ import (
 	"encoding/json"
 	"fmt"
 	"os"
+	"strings"
 
 	pb "github.com/prometheus/alertmanager/silence/silencepb"
 	"xorm.io/xorm"
@@ -217,7 +218,14 @@ func (m *migration) Exec(sess *xorm.Session, mg *migrator.Migrator) error {
 			return err
 		}
 
+		if strings.HasPrefix(mg.Dialect.DriverName(), migrator.Postgres) {
+			err = mg.InTransaction(func(sess *xorm.Session) error {
+				_, err = sess.Insert(rule)
+				return err
+			})
+		} else {
 			_, err = m.sess.Insert(rule)
+		}
 		if err != nil {
 			// TODO better error handling, if constraint
 			rule.Title += fmt.Sprintf(" %v", rule.Uid)

pkg/services/sqlstore/migrator/migrator.go

@@ -103,7 +103,7 @@ func (mg *Migrator) Start() error {
 			Timestamp:   time.Now(),
 		}
 
-		err := mg.inTransaction(func(sess *xorm.Session) error {
+		err := mg.InTransaction(func(sess *xorm.Session) error {
 			err := mg.exec(m, sess)
 			if err != nil {
 				mg.Logger.Error("Exec failed", "error", err, "sql", sql)
@@ -183,7 +183,7 @@ func (mg *Migrator) ClearMigrationEntry(id string) error {
 
 type dbTransactionFunc func(sess *xorm.Session) error
 
-func (mg *Migrator) inTransaction(callback dbTransactionFunc) error {
+func (mg *Migrator) InTransaction(callback dbTransactionFunc) error {
 	sess := mg.x.NewSession()
 	defer sess.Close()