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postgres.go
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postgres.go
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// Package postgres implements the Driver interface.
package postgres
import (
"database/sql"
"fmt"
"strconv"
"strings"
"github.com/db-journey/migrate/v2/direction"
"github.com/db-journey/migrate/v2/driver"
"github.com/db-journey/migrate/v2/file"
"github.com/lib/pq"
)
var fileTemplate = []byte(``) // TODO
// Driver is the postgres driver for journey.
type Driver struct {
db *sql.DB
}
const tableName = "public.schema_migrations"
const txDisabledOption = "disable_ddl_transaction"
// Open opens and verifies the database handle.
func Open(url string) (driver.Driver, error) {
driver := &Driver{}
db, err := sql.Open("postgres", url)
if err != nil {
return nil, err
}
if err := db.Ping(); err != nil {
return nil, err
}
driver.db = db
return driver, driver.ensureVersionTableExists()
}
// SetDB replaces the current database handle.
func (driver *Driver) SetDB(db *sql.DB) {
driver.db = db
}
// Close closes the database handle.
func (driver *Driver) Close() error {
return driver.db.Close()
}
func (driver *Driver) ensureVersionTableExists() error {
// avoid DDL statements if possible for BDR (see #23)
var c int
if err := driver.db.QueryRow("SELECT count(*) FROM information_schema.tables WHERE table_name = $1", tableName).Scan(&c); err != nil {
return err
}
if c <= 0 {
_, err := driver.db.Exec("CREATE TABLE IF NOT EXISTS " + tableName + " (version bigint not null primary key)")
return err
}
// table schema_migrations already exists, check if the schema is correct, ie: version is a bigint
var dataType string
if err := driver.db.QueryRow("SELECT data_type FROM information_schema.columns where table_name = $1 and column_name = 'version'", tableName).Scan(&dataType); err != nil {
return err
}
if dataType == "bigint" {
return nil
}
_, err := driver.db.Exec("ALTER TABLE " + tableName + " ALTER COLUMN version TYPE bigint USING version::bigint")
return err
}
// Migrate performs the migration of any one file.
func (driver *Driver) Migrate(f file.File) (err error) {
var tx *sql.Tx
tx, err = driver.db.Begin()
if err != nil {
return err
}
defer func() {
if err != nil {
tx.Rollback()
}
}()
if f.Direction == direction.Up {
if _, err = tx.Exec("INSERT INTO "+tableName+" (version) VALUES ($1)", f.Version); err != nil {
return err
}
} else if f.Direction == direction.Down {
if _, err = tx.Exec("DELETE FROM "+tableName+" WHERE version=$1", f.Version); err != nil {
return err
}
}
if err = f.ReadContent(); err != nil {
return err
}
if txDisabled(fileOptions(f.Content)) {
_, err = driver.db.Exec(string(f.Content))
} else {
_, err = tx.Exec(string(f.Content))
}
if err != nil {
pqErr := err.(*pq.Error)
offset, err := strconv.Atoi(pqErr.Position)
if err == nil && offset >= 0 {
lineNo, columnNo := file.LineColumnFromOffset(f.Content, offset-1)
errorPart := file.LinesBeforeAndAfter(f.Content, lineNo, 5, 5, true)
return fmt.Errorf("%s %v: %s in line %v, column %v:\n\n%s", pqErr.Severity, pqErr.Code, pqErr.Message, lineNo, columnNo, string(errorPart))
}
return fmt.Errorf("%s %v: %s", pqErr.Severity, pqErr.Code, pqErr.Message)
}
return tx.Commit()
}
// Version returns the current migration version.
func (driver *Driver) Version() (file.Version, error) {
var version file.Version
err := driver.db.QueryRow("SELECT version FROM " + tableName + " ORDER BY version DESC LIMIT 1").Scan(&version)
if err == sql.ErrNoRows {
return version, nil
}
return version, err
}
// Versions returns the list of applied migrations.
func (driver *Driver) Versions() (file.Versions, error) {
rows, err := driver.db.Query("SELECT version FROM " + tableName + " ORDER BY version DESC")
if err != nil {
return nil, err
}
defer rows.Close()
versions := file.Versions{}
for rows.Next() {
var version file.Version
if err = rows.Scan(&version); err != nil {
return nil, err
}
versions = append(versions, version)
}
if err = rows.Err(); err != nil {
return nil, err
}
return versions, err
}
// Execute a SQL statement
func (driver *Driver) Execute(statement string) error {
_, err := driver.db.Exec(statement)
return err
}
// fileOptions returns the list of options extracted from the first line of the file content.
// Format: "-- <option1> <option2> <...>"
func fileOptions(content []byte) []string {
firstLine := strings.SplitN(string(content), "\n", 2)[0]
if !strings.HasPrefix(firstLine, "-- ") {
return []string{}
}
opts := strings.TrimPrefix(firstLine, "-- ")
return strings.Split(opts, " ")
}
func txDisabled(opts []string) bool {
for _, v := range opts {
if v == txDisabledOption {
return true
}
}
return false
}
func init() {
// According to the PostgreSQL documentation (section 32.1.1.2), postgres
// library supports two URI schemes: postgresql:// and postgres://
// https://www.postgresql.org/docs/current/static/libpq-connect.html#LIBPQ-CONNSTRING
driver.Register("postgres", "sql", fileTemplate, Open)
driver.Register("postgresql", "sql", fileTemplate, Open)
}