85 lines
2.3 KiB
Go
85 lines
2.3 KiB
Go
package wtdb
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import "github.com/coreos/bbolt"
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// migration is a function which takes a prior outdated version of the database
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// instances and mutates the key/bucket structure to arrive at a more
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// up-to-date version of the database.
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type migration func(tx *bbolt.Tx) error
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// version pairs a version number with the migration that would need to be
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// applied from the prior version to upgrade.
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type version struct {
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number uint32
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migration migration
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}
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// dbVersions stores all versions and migrations of the database. This list will
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// be used when opening the database to determine if any migrations must be
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// applied.
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var dbVersions = []version{
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{
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// Initial version requires no migration.
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number: 0,
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migration: nil,
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},
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}
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// getLatestDBVersion returns the last known database version.
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func getLatestDBVersion(versions []version) uint32 {
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return versions[len(versions)-1].number
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}
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// getMigrations returns a slice of all updates with a greater number that
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// curVersion that need to be applied to sync up with the latest version.
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func getMigrations(versions []version, curVersion uint32) []version {
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var updates []version
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for _, v := range versions {
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if v.number > curVersion {
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updates = append(updates, v)
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}
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}
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return updates
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}
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// getDBVersion retrieves the current database version from the metadata bucket
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// using the dbVersionKey.
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func getDBVersion(tx *bbolt.Tx) (uint32, error) {
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metadata := tx.Bucket(metadataBkt)
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if metadata == nil {
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return 0, ErrUninitializedDB
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}
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versionBytes := metadata.Get(dbVersionKey)
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if len(versionBytes) != 4 {
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return 0, ErrNoDBVersion
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}
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return byteOrder.Uint32(versionBytes), nil
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}
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// initDBVersion initializes the top-level metadata bucket and writes the passed
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// version number as the current version.
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func initDBVersion(tx *bbolt.Tx, version uint32) error {
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_, err := tx.CreateBucketIfNotExists(metadataBkt)
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if err != nil {
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return err
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}
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return putDBVersion(tx, version)
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}
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// putDBVersion stores the passed database version in the metadata bucket under
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// the dbVersionKey.
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func putDBVersion(tx *bbolt.Tx, version uint32) error {
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metadata := tx.Bucket(metadataBkt)
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if metadata == nil {
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return ErrUninitializedDB
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}
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versionBytes := make([]byte, 4)
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byteOrder.PutUint32(versionBytes, version)
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return metadata.Put(dbVersionKey, versionBytes)
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}
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