use go module for dependencies (#594)

common/sql.go

@@ -0,0 +1,76 @@
+// Copyright 2017 Vector Creations Ltd
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package common
+
+import (
+	"database/sql"
+
+	"github.com/lib/pq"
+)
+
+// A Transaction is something that can be committed or rolledback.
+type Transaction interface {
+	// Commit the transaction
+	Commit() error
+	// Rollback the transaction.
+	Rollback() error
+}
+
+// EndTransaction ends a transaction.
+// If the transaction succeeded then it is committed, otherwise it is rolledback.
+func EndTransaction(txn Transaction, succeeded *bool) {
+	if *succeeded {
+		txn.Commit() // nolint: errcheck
+	} else {
+		txn.Rollback() // nolint: errcheck
+	}
+}
+
+// WithTransaction runs a block of code passing in an SQL transaction
+// If the code returns an error or panics then the transactions is rolledback
+// Otherwise the transaction is committed.
+func WithTransaction(db *sql.DB, fn func(txn *sql.Tx) error) (err error) {
+	txn, err := db.Begin()
+	if err != nil {
+		return
+	}
+	succeeded := false
+	defer EndTransaction(txn, &succeeded)
+
+	err = fn(txn)
+	if err != nil {
+		return
+	}
+
+	succeeded = true
+	return
+}
+
+// TxStmt wraps an SQL stmt inside an optional transaction.
+// If the transaction is nil then it returns the original statement that will
+// run outside of a transaction.
+// Otherwise returns a copy of the statement that will run inside the transaction.
+func TxStmt(transaction *sql.Tx, statement *sql.Stmt) *sql.Stmt {
+	if transaction != nil {
+		statement = transaction.Stmt(statement)
+	}
+	return statement
+}
+
+// IsUniqueConstraintViolationErr returns true if the error is a postgresql unique_violation error
+func IsUniqueConstraintViolationErr(err error) bool {
+	pqErr, ok := err.(*pq.Error)
+	return ok && pqErr.Code == "23505"
+}