Made Version function public

database.go

@@ -19,11 +19,11 @@ func newDatabase(host string, port int, dbName, user, pass string) (dbase Databa
 
 func (dbase Database) sqlConnString() string {// {{{
 	return fmt.Sprintf(
-		"postgresql://%s:%s@%s:%d/%s?sslmode=disable",
+		"host=%s port=%d user=%s password=%s dbname=%s sslmode=disable",
-		dbase.Username,
-		dbase.Password,
 		dbase.Host,
 		dbase.Port,
+		dbase.Username,
+		dbase.Password,
 		dbase.DbName,
 	)
 }// }}}

schema.go

@@ -1,3 +1,22 @@
+/*
+Package dbschema is used to keep the SQL schema up to date.
+
+	func sqlProvider(dbName string, version int) (sql []byte, found bool) {
+		// read an SQL file and return the contents
+		return
+	}
+
+	upgrader := dbschema.NewUpgrader()
+	upgrader.SetSqlCallback(sqlProvider)
+
+	if err = upgrader.AddDatabase("127.0.0.1", 5432, "foo", "postgres", "password"); err != nil {
+		panic(err)
+	}
+
+	if err = upgrader.Run(); err != nil {
+		panic(err)
+	}
+*/
 package dbschema
 
 import (
@@ -8,8 +27,10 @@ import (
 	"database/sql"
 )
 
+// An upgrader verifies the schema for one or more databases and upgrades them if possible.
 type Upgrader struct {
-	databases map[string]Database
+	schema      string
+	databases   map[string]Database
 	logCallback func(string, string)
 	sqlCallback func(string, int) ([]byte, bool)
 }
@@ -21,7 +42,7 @@ type Database struct {
 	Username string
 	Password string
 
-	db *sql.DB
+	db       *sql.DB
 	upgrader *Upgrader
 }
 

upgrader.go

@@ -1,6 +1,9 @@
 package dbschema
 
 import (
+	// External
+	"github.com/lib/pq"
+
 	// Standard
 	"database/sql"
 	"fmt"
@@ -9,18 +12,66 @@ import (
 func defaultCallback(topic, msg string) {// {{{
 	fmt.Printf("[%s] %s\n", topic, msg)
 }// }}}
-func NewUpgrader(host string, port int, dbName, user, pass string) (upgrader Upgrader, err error) {// {{{
+
+// NewUpgrader creates an upgrader with an empty list of databases.
+func NewUpgrader(schema ...string) (upgrader Upgrader) {// {{{
+	// Using a variadic function for backward compatibility.
+	if len(schema) > 0 {
+		upgrader.schema = schema[0]
+	} else {
+		upgrader.schema = "_db"
+	}
+
 	upgrader.logCallback = defaultCallback
 	upgrader.databases = map[string]Database{}
 	return
 }// }}}
 
+// SetLogCallback allows to set a callback for custom logging.
 func (upgrader *Upgrader) SetLogCallback(callback func(string, string)) {// {{{
 	upgrader.logCallback = callback
 }// }}}
+// SetSqlCallback is required for providing the SQL schema updates.
 func (upgrader *Upgrader) SetSqlCallback(callback func(string, int) ([]byte, bool)) {// {{{
 	upgrader.sqlCallback = callback
 }// }}}
+// Version returns the current dbschema version for the given database name.
+func (upgrader *Upgrader) Version(dbName string) (version int, err error) {// {{{
+	dbase, found := upgrader.databases[dbName]
+	if !found {
+		err = fmt.Errorf("Database %s not previously added to the upgrader", dbName)
+		return
+	}
+
+	version, err = dbase.Version()
+	return
+}// }}}
+
+func (dbase Database) createSchemaTable() (err error) {// {{{
+	dbase.upgrader.logCallback("create", fmt.Sprintf("%s, %s.schema", dbase.DbName, dbase.upgrader.schema))
+	_, err = dbase.db.Exec(`CREATE SCHEMA "`+dbase.upgrader.schema+`"`)
+
+	// Error code 42P06 "duplicate_schema" is an OK error,
+	// table can still be missing and created.
+	pqErr, _ := err.(*pq.Error)
+	if pqErr != nil && pqErr.Code != "42P06" {
+		return
+	}
+
+	_, err = dbase.db.Exec(`
+		CREATE TABLE "`+dbase.upgrader.schema+`"."schema" (
+			version  int4      NOT NULL,
+			updated  timestamp NOT NULL DEFAULT NOW(),
+
+			CONSTRAINT schema_pk PRIMARY KEY (version)
+		)`,
+	)
+	return
+}// }}}
+func (dbase Database) appendSchemaVersion(version int) (err error) {// {{{
+	_, err = dbase.db.Exec(`INSERT INTO `+dbase.upgrader.schema+`.schema(version) VALUES($1)`, version)
+	return
+}// }}}
 
 func (dbase Database) verifySchemaTable() (err error) {// {{{
 	var rows *sql.Rows
@@ -28,7 +79,7 @@ func (dbase Database) verifySchemaTable() (err error) {// {{{
 		`SELECT EXISTS (
 			SELECT FROM pg_catalog.pg_class c
 			JOIN   pg_catalog.pg_namespace n ON n.oid = c.relnamespace
-			WHERE  n.nspname = '_db'
+			WHERE  n.nspname = '`+dbase.upgrader.schema+`'
 			AND    c.relname = 'schema'
 		)`,
 	); err != nil {
@@ -41,45 +92,29 @@ func (dbase Database) verifySchemaTable() (err error) {// {{{
 		return
 	}
 
-	if !exists {
+	if exists {
-		dbase.upgrader.logCallback("create", fmt.Sprintf("%s, _db.schema", dbase.DbName))
+		return
-		dbase.db.Exec(`CREATE SCHEMA "_db"`)
-
-		if _, err = dbase.db.Exec(`
-			CREATE TABLE "_db"."schema" (
-				version  int4      NOT NULL,
-				updated  timestamp NOT NULL DEFAULT NOW(),
-
-				CONSTRAINT schema_pk PRIMARY KEY (version)
-			)`,
-		); err != nil {
-			return
-		}
 	}
+	err = dbase.createSchemaTable()
 	return
 }// }}}
 func (dbase Database) verifySchemaEntry() (err error) {// {{{
-	var rows *sql.Rows
+	var version int
-	rows, err = dbase.db.Query(`SELECT version FROM _db.schema LIMIT 1`)
+	var row *sql.Row
-	if err != nil {
+	row = dbase.db.QueryRow(`SELECT version FROM `+dbase.upgrader.schema+`.schema LIMIT 1`)
-		return
-	}
-	defer rows.Close()
 
-	if !rows.Next() {
+	err = row.Scan(&version)
+	if err == sql.ErrNoRows {
 		dbase.upgrader.logCallback("initiate version", dbase.DbName)
-		_, err = dbase.db.Exec(`INSERT INTO _db.schema(version) VALUES(0)`)
+		err = dbase.appendSchemaVersion(0)
-		if err != nil {
-			return
-		}
 	}
 
 	return
 }// }}}
-func (dbase Database) version() (version int, err error) {// {{{
+func (dbase Database) Version() (version int, err error) {// {{{
 	var rows *sql.Rows
 	rows, err = dbase.db.Query(
-		`SELECT version FROM _db.schema ORDER BY version DESC LIMIT 1`,
+		`SELECT version FROM `+dbase.upgrader.schema+`.schema ORDER BY version DESC LIMIT 1`,
 	)
 	if err != nil {
 		return
@@ -89,13 +124,13 @@ func (dbase Database) version() (version int, err error) {// {{{
 	if rows.Next() {
 		err = rows.Scan(&version)
 	} else {
-		err = fmt.Errorf(`Database "%s" is missing an entry in _db.schema`, dbase.DbName)
+		err = fmt.Errorf(`Database "%s" is missing an entry in `+dbase.upgrader.schema+`.schema`, dbase.DbName)
 	}
 	return
 }// }}}
 
-func (upgrader Upgrader) AddDatabase(host string, port int, dbName, user, pass string) (err error) {// {{{
+// AddDatabase sets a database up for the Run() function with verifying/creating the _db.schema table.
-	var db Database
+func (upgrader Upgrader) AddDatabase(host string, port int, dbName, user, pass string) (db Database, err error) {// {{{
 	if db, err = newDatabase(host, port, dbName, user, pass); err != nil {
 		return
 	}
@@ -110,15 +145,16 @@ func (upgrader Upgrader) AddDatabase(host string, port int, dbName, user, pass s
 	err = db.verifySchemaEntry()
 	return
 }// }}}
+// Run executes the actual schema updates until there are no more available.
 func (upgrader Upgrader) Run() (err error) {// {{{
 	var version int
 
 	for dbName, dbase := range upgrader.databases {
-		version, err = dbase.version()
+		version, err = dbase.Version()
 		if err != nil {
 			return
 		}
-		upgrader.logCallback("version", fmt.Sprintf("%s: %d", dbName, version))
+		upgrader.logCallback("version", fmt.Sprintf("%s.%s: %d", dbName, upgrader.schema, version))
 
 		for {
 			version++
@@ -127,15 +163,11 @@ func (upgrader Upgrader) Run() (err error) {// {{{
 				break
 			}
 
-			upgrader.logCallback("exec", fmt.Sprintf("%s: %d", dbName, version))
+			upgrader.logCallback("exec", fmt.Sprintf("%s.%s: %d", dbName, upgrader.schema, version))
 			if _, err = dbase.db.Exec(string(sql)); err != nil {
 				return
 			}
-			_, err = dbase.db.Exec(`
+			if err = dbase.appendSchemaVersion(version); err != nil {
-				INSERT INTO _db.schema(version)
-				VALUES($1)
-			`, version)
-			if err != nil {
 				return
 			}
 		}