tidb chunk 源码
tidb chunk 代码
文件路径：/util/chunk/chunk.go
// 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,
// 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 chunk
import (
"unsafe"
"github.com/pingcap/errors"
"github.com/pingcap/tidb/types"
"github.com/pingcap/tidb/util/mathutil"
)
var msgErrSelNotNil = "The selection vector of Chunk is not nil. Please file a bug to the TiDB Team"
// Chunk stores multiple rows of data in columns. Columns are in Apache Arrow format.
// See https://arrow.apache.org/docs/format/Columnar.html#physical-memory-layout.
// Apache Arrow is not used directly because we want to access MySQL types without decoding.
//
// Values are appended in compact format and can be directly accessed without decoding.
// When the chunk is done processing, we can reuse the allocated memory by resetting it.
//
// All Chunk's API should not do the validation work, and the user should ensure it is used correctly.
type Chunk struct {
// sel indicates which rows are selected.
// If it is nil, all rows are selected.
sel []int
columns []*Column
// numVirtualRows indicates the number of virtual rows, which have zero Column.
// It is used only when this Chunk doesn't hold any data, i.e. "len(columns)==0".
numVirtualRows int
// capacity indicates the max number of rows this chunk can hold.
// TODO: replace all usages of capacity to requiredRows and remove this field
capacity int
// requiredRows indicates how many rows the parent executor want.
requiredRows int
}
// Capacity constants.
const (
InitialCapacity = 32
ZeroCapacity = 0
)
// NewChunkWithCapacity creates a new chunk with field types and capacity.
func NewChunkWithCapacity(fields []*types.FieldType, capacity int) *Chunk {
return New(fields, capacity, capacity)
}
// New creates a new chunk.
//
// cap: the limit for the max number of rows.
// maxChunkSize: the max limit for the number of rows.
func New(fields []*types.FieldType, capacity, maxChunkSize int) *Chunk {
chk := &Chunk{
columns: make([]*Column, 0, len(fields)),
capacity: mathutil.Min(capacity, maxChunkSize),
// set the default value of requiredRows to maxChunkSize to let chk.IsFull() behave
// like how we judge whether a chunk is full now, then the statement
// "chk.NumRows() < maxChunkSize"
// equals to "!chk.IsFull()".
requiredRows: maxChunkSize,
}
for _, f := range fields {
chk.columns = append(chk.columns, NewColumn(f, chk.capacity))
}
return chk
}
// renewWithCapacity creates a new Chunk based on an existing Chunk with capacity. The newly
// created Chunk has the same data schema with the old Chunk.
func renewWithCapacity(chk *Chunk, capacity, requiredRows int) *Chunk {
if chk.columns == nil {
return &Chunk{}
}
return &Chunk{
columns: renewColumns(chk.columns, capacity),
numVirtualRows: 0,
capacity: capacity,
requiredRows: requiredRows,
}
}
// Renew creates a new Chunk based on an existing Chunk. The newly created Chunk
// has the same data schema with the old Chunk. The capacity of the new Chunk
// might be doubled based on the capacity of the old Chunk and the maxChunkSize.
//
// chk: old chunk(often used in previous call).
// maxChunkSize: the limit for the max number of rows.
func Renew(chk *Chunk, maxChunkSize int) *Chunk {
newCap := reCalcCapacity(chk, maxChunkSize)
return renewWithCapacity(chk, newCap, maxChunkSize)
}
// renewColumns creates the columns of a Chunk. The capacity of the newly
// created columns is equal to cap.
func renewColumns(oldCol []*Column, capacity int) []*Column {
columns := make([]*Column, 0, len(oldCol))
for _, col := range oldCol {
columns = append(columns, newColumn(col.typeSize(), capacity))
}
return columns
}
// renewEmpty creates a new Chunk based on an existing Chunk
// but keep columns empty.
func renewEmpty(chk *Chunk) *Chunk {
newChk := &Chunk{
columns: nil,
numVirtualRows: chk.numVirtualRows,
capacity: chk.capacity,
requiredRows: chk.requiredRows,
}
if chk.sel != nil {
newChk.sel = make([]int, len(chk.sel))
copy(newChk.sel, chk.sel)
}
return newChk
}
func (c *Chunk) resetForReuse() {
for i := 0; i < len(c.columns); i++ {
c.columns[i] = nil
}
columns := c.columns[:0]
// Keep only the empty columns array space, reset other fields.
*c = Chunk{columns: columns}
}
// MemoryUsage returns the total memory usage of a Chunk in bytes.
// We ignore the size of Column.length and Column.nullCount
// since they have little effect of the total memory usage.
func (c *Chunk) MemoryUsage() (sum int64) {
if c == nil {
return 0
}
for _, col := range c.columns {
curColMemUsage := int64(unsafe.Sizeof(*col)) + int64(cap(col.nullBitmap)) + int64(cap(col.offsets)*8) + int64(cap(col.data)) + int64(cap(col.elemBuf))
sum += curColMemUsage
}
return
}
// RequiredRows returns how many rows is considered full.
func (c *Chunk) RequiredRows() int {
return c.requiredRows
}
// SetRequiredRows sets the number of required rows.
func (c *Chunk) SetRequiredRows(requiredRows, maxChunkSize int) *Chunk {
if requiredRows <= 0 || requiredRows > maxChunkSize {
requiredRows = maxChunkSize
}
c.requiredRows = requiredRows
return c
}
// IsFull returns if this chunk is considered full.
func (c *Chunk) IsFull() bool {
return c.NumRows() >= c.requiredRows
}
// Prune creates a new Chunk according to `c` and prunes the columns
// whose index is not in `usedColIdxs`
func (c *Chunk) Prune(usedColIdxs []int) *Chunk {
chk := renewEmpty(c)
chk.columns = make([]*Column, len(usedColIdxs))
for i, idx := range usedColIdxs {
chk.columns[i] = c.columns[idx]
}
return chk
}
// MakeRef makes Column in "dstColIdx" reference to Column in "srcColIdx".
func (c *Chunk) MakeRef(srcColIdx, dstColIdx int) {
c.columns[dstColIdx] = c.columns[srcColIdx]
}
// MakeRefTo copies columns `src.columns[srcColIdx]` to `c.columns[dstColIdx]`.
func (c *Chunk) MakeRefTo(dstColIdx int, src *Chunk, srcColIdx int) error {
if c.sel != nil || src.sel != nil {
return errors.New(msgErrSelNotNil)
}
c.columns[dstColIdx] = src.columns[srcColIdx]
return nil
}
// SwapColumn swaps Column "c.columns[colIdx]" with Column
// "other.columns[otherIdx]". If there exists columns refer to the Column to be
// swapped, we need to re-build the reference.
func (c *Chunk) SwapColumn(colIdx int, other *Chunk, otherIdx int) error {
if c.sel != nil || other.sel != nil {
return errors.New(msgErrSelNotNil)
}
// Find the leftmost Column of the reference which is the actual Column to
// be swapped.
for i := 0; i < colIdx; i++ {
if c.columns[i] == c.columns[colIdx] {
colIdx = i
}
}
for i := 0; i < otherIdx; i++ {
if other.columns[i] == other.columns[otherIdx] {
otherIdx = i
}
}
// Find the columns which refer to the actual Column to be swapped.
refColsIdx := make([]int, 0, len(c.columns)-colIdx)
for i := colIdx; i < len(c.columns); i++ {
if c.columns[i] == c.columns[colIdx] {
refColsIdx = append(refColsIdx, i)
}
}
refColsIdx4Other := make([]int, 0, len(other.columns)-otherIdx)
for i := otherIdx; i < len(other.columns); i++ {
if other.columns[i] == other.columns[otherIdx] {
refColsIdx4Other = append(refColsIdx4Other, i)
}
}
// Swap columns from two chunks.
c.columns[colIdx], other.columns[otherIdx] = other.columns[otherIdx], c.columns[colIdx]
// Rebuild the reference.
for _, i := range refColsIdx {
c.MakeRef(colIdx, i)
}
for _, i := range refColsIdx4Other {
other.MakeRef(otherIdx, i)
}
return nil
}
// SwapColumns swaps columns with another Chunk.
func (c *Chunk) SwapColumns(other *Chunk) {
c.sel, other.sel = other.sel, c.sel
c.columns, other.columns = other.columns, c.columns
c.numVirtualRows, other.numVirtualRows = other.numVirtualRows, c.numVirtualRows
}
// SetNumVirtualRows sets the virtual row number for a Chunk.
// It should only be used when there exists no Column in the Chunk.
func (c *Chunk) SetNumVirtualRows(numVirtualRows int) {
c.numVirtualRows = numVirtualRows
}
// Reset resets the chunk, so the memory it allocated can be reused.
// Make sure all the data in the chunk is not used anymore before you reuse this chunk.
func (c *Chunk) Reset() {
c.sel = nil
if c.columns == nil {
return
}
for _, col := range c.columns {
col.reset()
}
c.numVirtualRows = 0
}
// CopyConstruct creates a new chunk and copies this chunk's data into it.
func (c *Chunk) CopyConstruct() *Chunk {
newChk := renewEmpty(c)
newChk.columns = make([]*Column, len(c.columns))
for i := range c.columns {
newChk.columns[i] = c.columns[i].CopyConstruct(nil)
}
return newChk
}
// CopyConstructSel is just like CopyConstruct,
// but ignore the rows that was not selected.
func (c *Chunk) CopyConstructSel() *Chunk {
if c.sel == nil {
return c.CopyConstruct()
}
newChk := renewWithCapacity(c, c.capacity, c.requiredRows)
for colIdx, dstCol := range newChk.columns {
for _, rowIdx := range c.sel {
appendCellByCell(dstCol, c.columns[colIdx], rowIdx)
}
}
return newChk
}
// GrowAndReset resets the Chunk and doubles the capacity of the Chunk.
// The doubled capacity should not be larger than maxChunkSize.
func (c *Chunk) GrowAndReset(maxChunkSize int) {
c.sel = nil
if c.columns == nil {
return
}
newCap := reCalcCapacity(c, maxChunkSize)
if newCap <= c.capacity {
c.Reset()
return
}
c.capacity = newCap
c.columns = renewColumns(c.columns, newCap)
c.numVirtualRows = 0
c.requiredRows = maxChunkSize
}
// reCalcCapacity calculates the capacity for another Chunk based on the current
// Chunk. The new capacity is doubled only when the current Chunk is full.
func reCalcCapacity(c *Chunk, maxChunkSize int) int {
if c.NumRows() < c.capacity {
return c.capacity
}
newCapacity := c.capacity * 2
if newCapacity == 0 {
newCapacity = InitialCapacity
}
return mathutil.Min(newCapacity, maxChunkSize)
}
// Capacity returns the capacity of the Chunk.
func (c *Chunk) Capacity() int {
if c == nil {
return 0
}
return c.capacity
}
// NumCols returns the number of columns in the chunk.
func (c *Chunk) NumCols() int {
return len(c.columns)
}
// NumRows returns the number of rows in the chunk.
func (c *Chunk) NumRows() int {
if c.sel != nil {
return len(c.sel)
}
if c.NumCols() == 0 {
return c.numVirtualRows
}
return c.columns[0].length
}
// GetRow gets the Row in the chunk with the row index.
func (c *Chunk) GetRow(idx int) Row {
if c.sel != nil {
// mapping the logical RowIdx to the actual physical RowIdx;
// for example, if the Sel is [1, 5, 6], then
// logical 0 -> physical 1,
// logical 1 -> physical 5,
// logical 2 -> physical 6.
// Then when we iterate this Chunk according to Row, only selected rows will be
// accessed while all filtered rows will be ignored.
return Row{c: c, idx: c.sel[idx]}
}
return Row{c: c, idx: idx}
}
// AppendRow appends a row to the chunk.
func (c *Chunk) AppendRow(row Row) {
c.AppendPartialRow(0, row)
c.numVirtualRows++
}
// AppendPartialRow appends a row to the chunk, starting from colOff.
func (c *Chunk) AppendPartialRow(colOff int, row Row) {
c.appendSel(colOff)
for i, rowCol := range row.c.columns {
chkCol := c.columns[colOff+i]
appendCellByCell(chkCol, rowCol, row.idx)
}
}
// AppendRowByColIdxs appends a row to the chunk, using the row's columns specified by colIdxs.
// 1. every columns are used if colIdxs is nil.
// 2. no columns are used if colIdxs is not nil but the size of colIdxs is 0.
func (c *Chunk) AppendRowByColIdxs(row Row, colIdxs []int) (wide int) {
wide = c.AppendPartialRowByColIdxs(0, row, colIdxs)
c.numVirtualRows++
return
}
// AppendPartialRowByColIdxs appends a row to the chunk starting from colOff,
// using the row's columns specified by colIdxs.
// 1. every columns are used if colIdxs is nil.
// 2. no columns are used if colIdxs is not nil but the size of colIdxs is 0.
func (c *Chunk) AppendPartialRowByColIdxs(colOff int, row Row, colIdxs []int) (wide int) {
if colIdxs == nil {
c.AppendPartialRow(colOff, row)
return row.Len()
}
c.appendSel(colOff)
for i, colIdx := range colIdxs {
rowCol := row.c.columns[colIdx]
chkCol := c.columns[colOff+i]
appendCellByCell(chkCol, rowCol, row.idx)
}
return len(colIdxs)
}
// appendCellByCell appends the cell with rowIdx of src into dst.
func appendCellByCell(dst *Column, src *Column, rowIdx int) {
dst.appendNullBitmap(!src.IsNull(rowIdx))
if src.isFixed() {
elemLen := len(src.elemBuf)
offset := rowIdx * elemLen
dst.data = append(dst.data, src.data[offset:offset+elemLen]...)
} else {
start, end := src.offsets[rowIdx], src.offsets[rowIdx+1]
dst.data = append(dst.data, src.data[start:end]...)
dst.offsets = append(dst.offsets, int64(len(dst.data)))
}
dst.length++
}
// Append appends rows in [begin, end) in another Chunk to a Chunk.
func (c *Chunk) Append(other *Chunk, begin, end int) {
for colID, src := range other.columns {
dst := c.columns[colID]
if src.isFixed() {
elemLen := len(src.elemBuf)
dst.data = append(dst.data, src.data[begin*elemLen:end*elemLen]...)
} else {
beginOffset, endOffset := src.offsets[begin], src.offsets[end]
dst.data = append(dst.data, src.data[beginOffset:endOffset]...)
lastOffset := dst.offsets[len(dst.offsets)-1]
for i := begin; i < end; i++ {
lastOffset += src.offsets[i+1] - src.offsets[i]
dst.offsets = append(dst.offsets, lastOffset)
}
}
for i := begin; i < end; i++ {
c.appendSel(colID)
dst.appendNullBitmap(!src.IsNull(i))
dst.length++
}
}
c.numVirtualRows += end - begin
}
// TruncateTo truncates rows from tail to head in a Chunk to "numRows" rows.
func (c *Chunk) TruncateTo(numRows int) {
c.Reconstruct()
for _, col := range c.columns {
if col.isFixed() {
elemLen := len(col.elemBuf)
col.data = col.data[:numRows*elemLen]
} else {
col.data = col.data[:col.offsets[numRows]]
col.offsets = col.offsets[:numRows+1]
}
col.length = numRows
bitmapLen := (col.length + 7) / 8
col.nullBitmap = col.nullBitmap[:bitmapLen]
if col.length%8 != 0 {
// When we append null, we simply increment the nullCount,
// so we need to clear the unused bits in the last bitmap byte.
lastByte := col.nullBitmap[bitmapLen-1]
unusedBitsLen := 8 - uint(col.length%8)
lastByte <<= unusedBitsLen
lastByte >>= unusedBitsLen
col.nullBitmap[bitmapLen-1] = lastByte
}
}
c.numVirtualRows = numRows
}
// AppendNull appends a null value to the chunk.
func (c *Chunk) AppendNull(colIdx int) {
c.appendSel(colIdx)
c.columns[colIdx].AppendNull()
}
// AppendInt64 appends a int64 value to the chunk.
func (c *Chunk) AppendInt64(colIdx int, i int64) {
c.appendSel(colIdx)
c.columns[colIdx].AppendInt64(i)
}
// AppendUint64 appends a uint64 value to the chunk.
func (c *Chunk) AppendUint64(colIdx int, u uint64) {
c.appendSel(colIdx)
c.columns[colIdx].AppendUint64(u)
}
// AppendFloat32 appends a float32 value to the chunk.
func (c *Chunk) AppendFloat32(colIdx int, f float32) {
c.appendSel(colIdx)
c.columns[colIdx].AppendFloat32(f)
}
// AppendFloat64 appends a float64 value to the chunk.
func (c *Chunk) AppendFloat64(colIdx int, f float64) {
c.appendSel(colIdx)
c.columns[colIdx].AppendFloat64(f)
}
// AppendString appends a string value to the chunk.
func (c *Chunk) AppendString(colIdx int, str string) {
c.appendSel(colIdx)
c.columns[colIdx].AppendString(str)
}
// AppendBytes appends a bytes value to the chunk.
func (c *Chunk) AppendBytes(colIdx int, b []byte) {
c.appendSel(colIdx)
c.columns[colIdx].AppendBytes(b)
}
// AppendTime appends a Time value to the chunk.
func (c *Chunk) AppendTime(colIdx int, t types.Time) {
c.appendSel(colIdx)
c.columns[colIdx].AppendTime(t)
}
// AppendDuration appends a Duration value to the chunk.
// Fsp is ignored.
func (c *Chunk) AppendDuration(colIdx int, dur types.Duration) {
c.appendSel(colIdx)
c.columns[colIdx].AppendDuration(dur)
}
// AppendMyDecimal appends a MyDecimal value to the chunk.
func (c *Chunk) AppendMyDecimal(colIdx int, dec *types.MyDecimal) {
c.appendSel(colIdx)
c.columns[colIdx].AppendMyDecimal(dec)
}
// AppendEnum appends an Enum value to the chunk.
func (c *Chunk) AppendEnum(colIdx int, enum types.Enum) {
c.appendSel(colIdx)
c.columns[colIdx].appendNameValue(enum.Name, enum.Value)
}
// AppendSet appends a Set value to the chunk.
func (c *Chunk) AppendSet(colIdx int, set types.Set) {
c.appendSel(colIdx)
c.columns[colIdx].appendNameValue(set.Name, set.Value)
}
// AppendJSON appends a JSON value to the chunk.
func (c *Chunk) AppendJSON(colIdx int, j types.BinaryJSON) {
c.appendSel(colIdx)
c.columns[colIdx].AppendJSON(j)
}
func (c *Chunk) appendSel(colIdx int) {
if colIdx == 0 && c.sel != nil { // use column 0 as standard
c.sel = append(c.sel, c.columns[0].length)
}
}
// AppendDatum appends a datum into the chunk.
func (c *Chunk) AppendDatum(colIdx int, d *types.Datum) {
switch d.Kind() {
case types.KindNull:
c.AppendNull(colIdx)
case types.KindInt64:
c.AppendInt64(colIdx, d.GetInt64())
case types.KindUint64:
c.AppendUint64(colIdx, d.GetUint64())
case types.KindFloat32:
c.AppendFloat32(colIdx, d.GetFloat32())
case types.KindFloat64:
c.AppendFloat64(colIdx, d.GetFloat64())
case types.KindString, types.KindBytes, types.KindBinaryLiteral, types.KindRaw, types.KindMysqlBit:
c.AppendBytes(colIdx, d.GetBytes())
case types.KindMysqlDecimal:
c.AppendMyDecimal(colIdx, d.GetMysqlDecimal())
case types.KindMysqlDuration:
c.AppendDuration(colIdx, d.GetMysqlDuration())
case types.KindMysqlEnum:
c.AppendEnum(colIdx, d.GetMysqlEnum())
case types.KindMysqlSet:
c.AppendSet(colIdx, d.GetMysqlSet())
case types.KindMysqlTime:
c.AppendTime(colIdx, d.GetMysqlTime())
case types.KindMysqlJSON:
c.AppendJSON(colIdx, d.GetMysqlJSON())
}
}
// Column returns the specific column.
func (c *Chunk) Column(colIdx int) *Column {
return c.columns[colIdx]
}
// SetCol sets the colIdx Column to col and returns the old Column.
func (c *Chunk) SetCol(colIdx int, col *Column) *Column {
if col == c.columns[colIdx] {
return nil
}
old := c.columns[colIdx]
c.columns[colIdx] = col
return old
}
// Sel returns Sel of this Chunk.
func (c *Chunk) Sel() []int {
return c.sel
}
// SetSel sets a Sel for this Chunk.
func (c *Chunk) SetSel(sel []int) {
c.sel = sel
}
// Reconstruct removes all filtered rows in this Chunk.
func (c *Chunk) Reconstruct() {
if c.sel == nil {
return
}
for _, col := range c.columns {
col.reconstruct(c.sel)
}
c.numVirtualRows = len(c.sel)
c.sel = nil
}
// ToString returns all the values in a chunk.
func (c *Chunk) ToString(ft []*types.FieldType) string {
var buf []byte
for rowIdx := 0; rowIdx < c.NumRows(); rowIdx++ {
row := c.GetRow(rowIdx)
buf = append(buf, row.ToString(ft)...)
buf = append(buf, '\n')
}
return string(buf)
}
// AppendRows appends multiple rows to the chunk.
func (c *Chunk) AppendRows(rows []Row) {
c.AppendPartialRows(0, rows)
c.numVirtualRows += len(rows)
}
// AppendPartialRows appends multiple rows to the chunk.
func (c *Chunk) AppendPartialRows(colOff int, rows []Row) {
columns := c.columns[colOff:]
for i, dstCol := range columns {
for _, srcRow := range rows {
if i == 0 {
c.appendSel(colOff)
}
appendCellByCell(dstCol, srcRow.c.columns[i], srcRow.idx)
}
}
}
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