Golang Context.KeyRange方法代码示例

// DeleteAll deletes all key-value associated with a context (data instance and version).
func (db *KVAutobus) DeleteAll(ctx storage.Context, allVersions bool) error {
	if ctx == nil {
		return fmt.Errorf("Received nil context in DeleteAll()")
	}
	if !allVersions {
		return fmt.Errorf("DeleteAll() not supported for immutable store unless for all versions")
	}
	keyBeg, keyEnd := ctx.KeyRange()
	return db.deleteRange(keyBeg, keyEnd)
}

func (db *LevelDB) deleteAllVersions(ctx storage.Context) error {
	dvid.StartCgo()

	var err error
	var minKey, maxKey storage.Key

	vctx, versioned := ctx.(storage.VersionedCtx)
	if versioned {
		// Don't have to worry about tombstones.  Delete all keys from all versions for this instance id.
		minTKey := storage.MinTKey(storage.TKeyMinClass)
		maxTKey := storage.MaxTKey(storage.TKeyMaxClass)
		minKey, err = vctx.MinVersionKey(minTKey)
		if err != nil {
			return err
		}
		maxKey, err = vctx.MaxVersionKey(maxTKey)
		if err != nil {
			return err
		}
	} else {
		minKey, maxKey = ctx.KeyRange()
	}

	const BATCH_SIZE = 10000
	batch := db.NewBatch(ctx).(*goBatch)

	ro := levigo.NewReadOptions()
	it := db.ldb.NewIterator(ro)
	defer func() {
		it.Close()
		dvid.StopCgo()
	}()

	numKV := 0
	it.Seek(minKey)
	for {
		if err := it.GetError(); err != nil {
			return fmt.Errorf("Error iterating during DeleteAll for %s: %v", ctx, err)
		}
		if it.Valid() {
			itKey := it.Key()
			storage.StoreKeyBytesRead <- len(itKey)
			// Did we pass the final key?
			if bytes.Compare(itKey, maxKey) > 0 {
				break
			}

			batch.WriteBatch.Delete(itKey)
			if (numKV+1)%BATCH_SIZE == 0 {
				if err := batch.Commit(); err != nil {
					dvid.Criticalf("Error on batch commit of DeleteAll at key-value pair %d: %v\n", numKV, err)
					return fmt.Errorf("Error on batch commit of DeleteAll at key-value pair %d: %v", numKV, err)
				}
				batch = db.NewBatch(ctx).(*goBatch)
				dvid.Debugf("Deleted %d key-value pairs in ongoing DELETE ALL for %s.\n", numKV+1, ctx)
			}
			numKV++
			it.Next()
		} else {
			break
		}
	}
	if numKV%BATCH_SIZE != 0 {
		if err := batch.Commit(); err != nil {
			dvid.Criticalf("Error on last batch commit of DeleteAll: %v\n", err)
			return fmt.Errorf("Error on last batch commit of DeleteAll: %v", err)
		}
	}
	dvid.Debugf("Deleted %d key-value pairs via DELETE ALL for %s.\n", numKV, ctx)
	return nil
}

// DeleteAll removes all key-value pairs for the context.  If allVersions is true,
// then all versions of the data instance are deleted.
func (db *BigTable) DeleteAll(ctx storage.Context, allVersions bool) error {
	if db == nil {
		return fmt.Errorf("Can't call DeleteAll() on nil BigTable")
	}
	if ctx == nil {
		return fmt.Errorf("Received nil context in DeleteAll()")
	}

	//Row range corresponde to all keys corresponding to this data instace.
	min, max := ctx.KeyRange()
	rr := api.NewRange(encodeKey(min), encodeKey(max))

	err := tbl.ReadRows(db.ctx, rr, func(r api.Row) bool {

		unvKeyRow, err := decodeKey(r.Key())
		if err != nil {
			dvid.Errorf("Error in DeleteAll(): %v\n", err)
			return false
		}

		if allVersions {

			mut := api.NewMutation()
			mut.DeleteRow()
			err := tbl.Apply(db.ctx, encodeKey(unvKeyRow), mut)
			if err != nil {
				dvid.Errorf("Failed to delete row")
			}
		} else {

			emptyTkey := make([]byte, 0)
			_, versionToDelete, err := ctx.SplitKey(emptyTkey)
			if err != nil {
				dvid.Errorf("Error in DeleteAll(): %v\n", err)
				return false
			}

			for _, readItem := range r[familyName] {

				verKey, err := decodeKey(readItem.Column)
				if err != nil {
					dvid.Errorf("Error in DeleteAll(): %v\n", err)
					return false
				}

				if bytes.Equal(verKey, versionToDelete) {
					mut := api.NewMutation()
					mut.DeleteCellsInColumn(familyName, encodeKey(verKey))
					err := tbl.Apply(db.ctx, encodeKey(unvKeyRow), mut)
					if err != nil {
						dvid.Errorf("Failed to DeleteCellsInColumn in DeleteAll()")
					}
					return true // One I found the version I don't have to keep serching for it.
				}
			}
		}

		return true // keep going
	}, api.RowFilter(api.StripValueFilter()))

	return err
}