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reverse.go
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reverse.go
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package main
import (
"fmt"
"github.com/bradfitz/slice"
"github.com/elwinar/rambler/log"
"github.com/urfave/cli"
)
// Reverse available migrations based on the provided context.
func Reverse(ctx *cli.Context) error {
return reverse(service, ctx.Bool("all"), !ctx.Bool("no-save"), ctx.String("migration"), logger)
}
func reverse(service Servicer, all, save bool, migration string, logger *log.Logger) error {
logger.Debug("checking database state")
initialized, err := service.Initialized()
if err != nil {
return fmt.Errorf("unable to check for database state: %s", err)
}
if !initialized {
return fmt.Errorf("uninitialized database")
}
var targets []*Migration
if migration != "" {
logger.Debug("fetching migration")
m, err := NewMigration(migration)
if err != nil {
return fmt.Errorf("unable to retrieve migration: %s", err)
}
targets = append(targets, m)
} else {
logger.Debug("fetching available migrations")
available, err := service.Available()
if err != nil {
return fmt.Errorf("unable to retrieve available migrations: %s", err)
}
logger.Info("found %d available migrations", len(available))
logger.Debug("fetching applied migrations")
applied, err := service.Applied()
if err != nil {
return fmt.Errorf("unable to retrieve applied migrations: %s", err)
}
logger.Info("found %d applied migrations", len(applied))
if len(applied) == 0 {
logger.Info("no migration to reverse")
return nil
}
logger.Debug("rewinding to first applied migration")
var i, j = len(available) - 1, len(applied) - 1
for i >= 0 && j >= 0 && available[i].Name > applied[j].Name {
i--
}
logger.Debug("comparing available and applied migrations")
for i >= 0 && j >= 0 {
logger.Debug("comparing %s and %s", available[i].Name, applied[j].Name)
if available[i].Name == applied[j].Name {
i--
j--
continue
}
if available[i].Name < applied[j].Name {
return fmt.Errorf("missing migration: %s", applied[j].Name)
}
if available[i].Name > applied[j].Name {
return fmt.Errorf("out of order migration: %s", available[i].Name)
}
}
if i >= 0 {
return fmt.Errorf("out of order migration: %s", available[i].Name)
}
if j >= 0 {
return fmt.Errorf("missing migration: %s", applied[j].Name)
}
targets = applied
}
logger.Debug("reversing order of applied migrations")
slice.Sort(targets, func(i, j int) bool {
return targets[i].Name > targets[j].Name
})
logger.Info("%d migrations to reverse", len(targets))
for _, migration := range targets {
logger.Info("reversing %s", migration.Name)
err := service.Reverse(migration, save)
if err != nil {
return err
}
if !all {
break
}
}
logger.Info("done")
return nil
}