Add support for loading go migrations from precompiled plugins (press…

…ly#24)

.travis.yml

@@ -1,7 +1,7 @@
 sudo: false
 language: go
 go:
-- 1.6
+- 1.8
 - tip
 
 install:

README.md

@@ -14,6 +14,8 @@ github.com/pressly/goose is a fork of bitbucket.org/liamstask/goose with the fol
     - Instead, you can create your own goose binary, import `github.com/pressly/goose`
       package and run complex Go migrations with your own `*sql.DB` connection
     - Each Go migration function is called with `*sql.Tx` argument - within its own transaction
+    - If a deployment model does not allow go compiler to be available from PATH it is possible
+      to load go migrations from one or more precompiled plugins (*.so)
 - The goose pkg is decoupled from the default binary:
     - goose pkg doesn't register any SQL drivers anymore
       (no driver `panic()` conflict within your codebase!)
@@ -173,7 +175,7 @@ language plpgsql;
 A [sample Go migration 00002_users_add_email.go file](./example/migrations-go/00002_rename_root.go) looks like:
 
 ```go
-package migrations
+package main
 
 import (
 	"database/sql"
@@ -202,6 +204,20 @@ func Down(tx *sql.Tx) error {
 }
 ```
 
+## Go Migrations from a precompiled plugins
+
+1. Import `github.com/pressly/goose`
+2. Load migration plugins with LoadMigrationPlugins
+4. Run goose command, ie. `goose.Up(db *sql.DB, dir string)`
+
+A migration plugin can be created from a go template generated by goose.
+Golang plugin system requires that the plugin's namespace is main.
+To compile a plugin one can use the following command:
+
+```bash
+go build -buildmode=plugin -o 002_next.so 002_next.sql
+```
+
 ## License
 
 Licensed under [MIT License](./LICENSE)

migrate.go

@@ -6,6 +6,7 @@ import (
 	"fmt"
 	"log"
 	"path/filepath"
+	"plugin"
 	"runtime"
 	"sort"
 )
@@ -128,6 +129,24 @@ func CollectMigrations(dirpath string, current, target int64) (Migrations, error
 	return migrations, nil
 }
 
+// LoadMigrationPlugins loads all the valid looking precompiled migration libraries
+// in the migrations folder and go func registry, and key them by version. Registration
+// is done automatically by shared library init func.
+func LoadMigrationPlugins(dirpath string) error {
+	migrationsPlugins, err := filepath.Glob(dirpath + "/*.so")
+	if err != nil {
+		return err
+	}
+
+	for _, file := range migrationsPlugins {
+		if _, err = plugin.Open(file); err != nil {
+			return err
+		}
+	}
+
+	return nil
+}
+
 func sortAndConnectMigrations(migrations Migrations) Migrations {
 	sort.Sort(migrations)
 

migration.go

@@ -27,6 +27,10 @@ type Migration struct {
 	DownFn   func(*sql.Tx) error // Down go migration function
 }
 
+type TemplateParams struct {
+	Version, Name string
+}
+
 func (m *Migration) String() string {
 	return fmt.Sprintf(m.Source)
 }
@@ -40,6 +44,7 @@ func (m *Migration) Down(db *sql.DB) error {
 }
 
 func (m *Migration) run(db *sql.DB, direction bool) error {
+
 	switch filepath.Ext(m.Source) {
 	case ".sql":
 		if err := runSQLMigration(db, m.Source, m.Version, direction); err != nil {
@@ -105,16 +110,16 @@ func CreateMigration(name, migrationType, dir string, t time.Time) (path string,
 		return "", errors.New("migration type must be 'go' or 'sql'")
 	}
 
-	timestamp := t.Format("20060102150405")
-	filename := fmt.Sprintf("%v_%v.%v", timestamp, name, migrationType)
+	version := t.Format("20060102150405")
+	filename := fmt.Sprintf("%v_%v.%v", version, name, migrationType)
 
 	fpath := filepath.Join(dir, filename)
 	tmpl := sqlMigrationTemplate
 	if migrationType == "go" {
-		tmpl = goSqlMigrationTemplate
+		tmpl = goMigrationTemplate
 	}
 
-	path, err = writeTemplateToFile(fpath, tmpl, timestamp)
+	path, err = writeTemplateToFile(fpath, tmpl, TemplateParams{Version: version, Name: filename})
 
 	return
 }
@@ -133,17 +138,18 @@ func FinalizeMigration(tx *sql.Tx, direction bool, v int64) error {
 	return tx.Commit()
 }
 
-var sqlMigrationTemplate = template.Must(template.New("goose.sql-migration").Parse(`
--- +goose Up
+var sqlMigrationTemplate = template.Must(template.New("goose.sql-migration").Parse(
+`-- +goose Up
 -- SQL in section 'Up' is executed when this migration is applied
 
 
 -- +goose Down
 -- SQL section 'Down' is executed when this migration is rolled back
 
 `))
-var goSqlMigrationTemplate = template.Must(template.New("goose.go-migration").Parse(`
-package migration
+
+var goMigrationTemplate = template.Must(template.New("goose.go-migration").Parse(
+`package main
 
 import (
     "database/sql"
@@ -152,14 +158,14 @@ import (
 )
 
 func init() {
-    goose.AddMigration(Up_{{.}}, Down_{{.}})
+    goose.AddNamedMigration("{{.Name}}", Up_{{.Version}}, Down_{{.Version}})
 }
 
-func Up_{{.}}(tx *sql.Tx) error {
+func Up_{{.Version}}(tx *sql.Tx) error {
     return nil
 }
 
-func Down_{{.}}(tx *sql.Tx) error {
+func Down_{{.Version}}(tx *sql.Tx) error {
     return nil
 }
 `))