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reader.go
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/*
Copyright 2016 Google Inc. All Rights Reserved.
Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at
http://www.apache.org/licenses/LICENSE-2.0
Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
*/
package bigtable
import (
"bytes"
"fmt"
btpb "google.golang.org/genproto/googleapis/bigtable/v2"
)
// A Row is returned by ReadRows. The map is keyed by column family (the prefix
// of the column name before the colon). The values are the returned ReadItems
// for that column family in the order returned by Read.
type Row map[string][]ReadItem
// Key returns the row's key, or "" if the row is empty.
func (r Row) Key() string {
for _, items := range r {
if len(items) > 0 {
return items[0].Row
}
}
return ""
}
// A ReadItem is returned by Read. A ReadItem contains data from a specific row and column.
type ReadItem struct {
Row, Column string
Timestamp Timestamp
Value []byte
}
// The current state of the read rows state machine.
type rrState int64
const (
newRow rrState = iota
rowInProgress
cellInProgress
)
// chunkReader handles cell chunks from the read rows response and combines
// them into full Rows.
type chunkReader struct {
state rrState
curKey []byte
curFam string
curQual []byte
curTS int64
curVal []byte
curRow Row
lastKey string
}
// newChunkReader returns a new chunkReader for handling read rows responses.
func newChunkReader() *chunkReader {
return &chunkReader{state: newRow}
}
// Process takes a cell chunk and returns a new Row if the given chunk
// completes a Row, or nil otherwise.
func (cr *chunkReader) Process(cc *btpb.ReadRowsResponse_CellChunk) (Row, error) {
var row Row
switch cr.state {
case newRow:
if err := cr.validateNewRow(cc); err != nil {
return nil, err
}
cr.curRow = make(Row)
cr.curKey = cc.RowKey
cr.curFam = cc.FamilyName.Value
cr.curQual = cc.Qualifier.Value
cr.curTS = cc.TimestampMicros
row = cr.handleCellValue(cc)
case rowInProgress:
if err := cr.validateRowInProgress(cc); err != nil {
return nil, err
}
if cc.GetResetRow() {
cr.resetToNewRow()
return nil, nil
}
if cc.FamilyName != nil {
cr.curFam = cc.FamilyName.Value
}
if cc.Qualifier != nil {
cr.curQual = cc.Qualifier.Value
}
cr.curTS = cc.TimestampMicros
row = cr.handleCellValue(cc)
case cellInProgress:
if err := cr.validateCellInProgress(cc); err != nil {
return nil, err
}
if cc.GetResetRow() {
cr.resetToNewRow()
return nil, nil
}
row = cr.handleCellValue(cc)
}
return row, nil
}
// Close must be called after all cell chunks from the response
// have been processed. An error will be returned if the reader is
// in an invalid state, in which case the error should be propagated to the caller.
func (cr *chunkReader) Close() error {
if cr.state != newRow {
return fmt.Errorf("invalid state for end of stream %q", cr.state)
}
return nil
}
// handleCellValue returns a Row if the cell value includes a commit, otherwise nil.
func (cr *chunkReader) handleCellValue(cc *btpb.ReadRowsResponse_CellChunk) Row {
if cc.ValueSize > 0 {
// ValueSize is specified so expect a split value of ValueSize bytes
if cr.curVal == nil {
cr.curVal = make([]byte, 0, cc.ValueSize)
}
cr.curVal = append(cr.curVal, cc.Value...)
cr.state = cellInProgress
} else {
// This cell is either the complete value or the last chunk of a split
if cr.curVal == nil {
cr.curVal = cc.Value
} else {
cr.curVal = append(cr.curVal, cc.Value...)
}
cr.finishCell()
if cc.GetCommitRow() {
return cr.commitRow()
} else {
cr.state = rowInProgress
}
}
return nil
}
func (cr *chunkReader) finishCell() {
ri := ReadItem{
Row: string(cr.curKey),
Column: fmt.Sprintf("%s:%s", cr.curFam, cr.curQual),
Timestamp: Timestamp(cr.curTS),
Value: cr.curVal,
}
cr.curRow[cr.curFam] = append(cr.curRow[cr.curFam], ri)
cr.curVal = nil
}
func (cr *chunkReader) commitRow() Row {
row := cr.curRow
cr.lastKey = cr.curRow.Key()
cr.resetToNewRow()
return row
}
func (cr *chunkReader) resetToNewRow() {
cr.curKey = nil
cr.curFam = ""
cr.curQual = nil
cr.curVal = nil
cr.curRow = nil
cr.curTS = 0
cr.state = newRow
}
func (cr *chunkReader) validateNewRow(cc *btpb.ReadRowsResponse_CellChunk) error {
if cc.GetResetRow() {
return fmt.Errorf("reset_row not allowed between rows")
}
if cc.RowKey == nil || cc.FamilyName == nil || cc.Qualifier == nil {
return fmt.Errorf("missing key field for new row %v", cc)
}
if cr.lastKey != "" && cr.lastKey >= string(cc.RowKey) {
return fmt.Errorf("out of order row key: %q, %q", cr.lastKey, string(cc.RowKey))
}
return nil
}
func (cr *chunkReader) validateRowInProgress(cc *btpb.ReadRowsResponse_CellChunk) error {
if err := cr.validateRowStatus(cc); err != nil {
return err
}
if cc.RowKey != nil && !bytes.Equal(cc.RowKey, cr.curKey) {
return fmt.Errorf("received new row key %q during existing row %q", cc.RowKey, cr.curKey)
}
if cc.FamilyName != nil && cc.Qualifier == nil {
return fmt.Errorf("family name %q specified without a qualifier", cc.FamilyName)
}
return nil
}
func (cr *chunkReader) validateCellInProgress(cc *btpb.ReadRowsResponse_CellChunk) error {
if err := cr.validateRowStatus(cc); err != nil {
return err
}
if cr.curVal == nil {
return fmt.Errorf("no cached cell while CELL_IN_PROGRESS %v", cc)
}
if cc.GetResetRow() == false && cr.isAnyKeyPresent(cc) {
return fmt.Errorf("cell key components found while CELL_IN_PROGRESS %v", cc)
}
return nil
}
func (cr *chunkReader) isAnyKeyPresent(cc *btpb.ReadRowsResponse_CellChunk) bool {
return cc.RowKey != nil ||
cc.FamilyName != nil ||
cc.Qualifier != nil ||
cc.TimestampMicros != 0
}
// Validate a RowStatus, commit or reset, if present.
func (cr *chunkReader) validateRowStatus(cc *btpb.ReadRowsResponse_CellChunk) error {
// Resets can't be specified with any other part of a cell
if cc.GetResetRow() && (cr.isAnyKeyPresent(cc) ||
cc.Value != nil ||
cc.ValueSize != 0 ||
cc.Labels != nil) {
return fmt.Errorf("reset must not be specified with other fields %v", cc)
}
if cc.GetCommitRow() && cc.ValueSize > 0 {
return fmt.Errorf("commit row found in between chunks in a cell")
}
return nil
}