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stream.go
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/
stream.go
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// Copyright 2017 PingCAP, Inc.
//
// 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,
// See the License for the specific language governing permissions and
// limitations under the License.
package distsql
import (
"github.com/juju/errors"
"github.com/pingcap/tidb/context"
"github.com/pingcap/tidb/kv"
"github.com/pingcap/tidb/types"
"github.com/pingcap/tidb/util/chunk"
"github.com/pingcap/tidb/util/codec"
"github.com/pingcap/tipb/go-tipb"
goctx "golang.org/x/net/context"
)
// streamResult implements the SelectResult interface.
type streamResult struct {
resp kv.Response
rowLen int
fieldTypes []*types.FieldType
ctx context.Context
// NOTE: curr == nil means stream finish, while len(curr.RowsData) == 0 doesn't.
curr *tipb.Chunk
scanCount int64
}
func (r *streamResult) ScanCount() int64 {
return r.scanCount
}
func (r *streamResult) Fetch(goctx.Context) {}
func (r *streamResult) Next(goctx.Context) (PartialResult, error) {
var ret streamPartialResult
ret.rowLen = r.rowLen
finished, err := r.readDataFromResponse(r.resp, &ret.Chunk)
if err != nil || finished {
return nil, errors.Trace(err)
}
return &ret, nil
}
func (r *streamResult) NextChunk(goCtx goctx.Context, chk *chunk.Chunk) error {
chk.Reset()
maxChunkSize := r.ctx.GetSessionVars().MaxChunkSize
for chk.NumRows() < maxChunkSize {
err := r.readDataIfNecessary()
if err != nil {
return errors.Trace(err)
}
if r.curr == nil {
return nil
}
err = r.flushToChunk(chk)
if err != nil {
return errors.Trace(err)
}
}
return nil
}
// readDataFromResponse read the data to result. Returns true means the resp is finished.
func (r *streamResult) readDataFromResponse(resp kv.Response, result *tipb.Chunk) (bool, error) {
data, err := resp.Next()
if err != nil {
return false, errors.Trace(err)
}
if data == nil {
return true, nil
}
var stream tipb.StreamResponse
err = stream.Unmarshal(data)
if err != nil {
return false, errors.Trace(err)
}
if stream.Error != nil {
return false, errors.Errorf("stream response error: [%d]%s\n", stream.Error.Code, stream.Error.Msg)
}
// TODO: Check stream.GetEncodeType() here if we support tipb.EncodeType_TypeArrow some day.
err = result.Unmarshal(stream.Data)
if err != nil {
return false, errors.Trace(err)
}
if len(stream.OutputCounts) > 0 {
r.scanCount += stream.OutputCounts[0]
}
return false, nil
}
// readDataIfNecessary ensures there are some data in current chunk. If no more data, r.curr == nil.
func (r *streamResult) readDataIfNecessary() error {
if r.curr != nil && len(r.curr.RowsData) > 0 {
return nil
}
tmp := new(tipb.Chunk)
finish, err := r.readDataFromResponse(r.resp, tmp)
if err != nil {
return errors.Trace(err)
}
if finish {
r.curr = nil
return nil
}
r.curr = tmp
return nil
}
func (r *streamResult) flushToChunk(chk *chunk.Chunk) (err error) {
remainRowsData := r.curr.RowsData
maxChunkSize := r.ctx.GetSessionVars().MaxChunkSize
timeZone := r.ctx.GetSessionVars().GetTimeZone()
for chk.NumRows() < maxChunkSize && len(remainRowsData) > 0 {
for i := 0; i < r.rowLen; i++ {
remainRowsData, err = codec.DecodeOneToChunk(remainRowsData, chk, i, r.fieldTypes[i], timeZone)
if err != nil {
return errors.Trace(err)
}
}
}
if len(remainRowsData) == 0 {
r.curr = nil // Current chunk is finished.
} else {
r.curr.RowsData = remainRowsData
}
return nil
}
func (r *streamResult) NextRaw() ([]byte, error) {
return r.resp.Next()
}
func (r *streamResult) Close() error {
return nil
}
// streamPartialResult implements PartialResult.
type streamPartialResult struct {
tipb.Chunk
rowLen int
}
func (pr *streamPartialResult) Next(goCtx goctx.Context) (data []types.Datum, err error) {
if len(pr.Chunk.RowsData) == 0 {
return nil, nil // partial result finished.
}
return readRowFromChunk(&pr.Chunk, pr.rowLen)
}
func (pr *streamPartialResult) Close() error {
return nil
}