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514 lines
15 KiB
514 lines
15 KiB
// Copyright 2019 PingCAP, Inc.
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// See the License for the specific language governing permissions and
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// limitations under the License.
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package executor
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import (
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"context"
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"github.com/cznic/mathutil"
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"github.com/pingcap/errors"
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"github.com/pingcap/parser/ast"
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"github.com/pingcap/tidb/executor/aggfuncs"
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"github.com/pingcap/tidb/expression"
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"github.com/pingcap/tidb/planner/core"
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"github.com/pingcap/tidb/sessionctx"
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"github.com/pingcap/tidb/util/chunk"
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)
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// WindowExec is the executor for window functions.
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type WindowExec struct {
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baseExecutor
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groupChecker *vecGroupChecker
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// childResult stores the child chunk
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childResult *chunk.Chunk
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// executed indicates the child executor is drained or something unexpected happened.
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executed bool
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// resultChunks stores the chunks to return
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resultChunks []*chunk.Chunk
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// remainingRowsInChunk indicates how many rows the resultChunks[i] is not prepared.
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remainingRowsInChunk []int
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numWindowFuncs int
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processor windowProcessor
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}
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// Close implements the Executor Close interface.
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func (e *WindowExec) Close() error {
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return errors.Trace(e.baseExecutor.Close())
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}
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// Next implements the Executor Next interface.
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func (e *WindowExec) Next(ctx context.Context, chk *chunk.Chunk) error {
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chk.Reset()
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for !e.executed && !e.preparedChunkAvailable() {
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err := e.consumeOneGroup(ctx)
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if err != nil {
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e.executed = true
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return err
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}
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}
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if len(e.resultChunks) > 0 {
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chk.SwapColumns(e.resultChunks[0])
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e.resultChunks[0] = nil // GC it. TODO: Reuse it.
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e.resultChunks = e.resultChunks[1:]
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e.remainingRowsInChunk = e.remainingRowsInChunk[1:]
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}
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return nil
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}
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func (e *WindowExec) preparedChunkAvailable() bool {
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return len(e.resultChunks) > 0 && e.remainingRowsInChunk[0] == 0
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}
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func (e *WindowExec) consumeOneGroup(ctx context.Context) error {
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var groupRows []chunk.Row
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if e.groupChecker.isExhausted() {
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eof, err := e.fetchChild(ctx)
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if err != nil {
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return errors.Trace(err)
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}
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if eof {
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e.executed = true
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return e.consumeGroupRows(groupRows)
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}
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_, err = e.groupChecker.splitIntoGroups(e.childResult)
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if err != nil {
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return errors.Trace(err)
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}
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}
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begin, end := e.groupChecker.getNextGroup()
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for i := begin; i < end; i++ {
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groupRows = append(groupRows, e.childResult.GetRow(i))
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}
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for meetLastGroup := end == e.childResult.NumRows(); meetLastGroup; {
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meetLastGroup = false
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eof, err := e.fetchChild(ctx)
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if err != nil {
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return errors.Trace(err)
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}
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if eof {
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e.executed = true
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return e.consumeGroupRows(groupRows)
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}
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isFirstGroupSameAsPrev, err := e.groupChecker.splitIntoGroups(e.childResult)
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if err != nil {
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return errors.Trace(err)
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}
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if isFirstGroupSameAsPrev {
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begin, end = e.groupChecker.getNextGroup()
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for i := begin; i < end; i++ {
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groupRows = append(groupRows, e.childResult.GetRow(i))
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}
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meetLastGroup = end == e.childResult.NumRows()
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}
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}
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return e.consumeGroupRows(groupRows)
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}
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func (e *WindowExec) consumeGroupRows(groupRows []chunk.Row) (err error) {
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remainingRowsInGroup := len(groupRows)
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if remainingRowsInGroup == 0 {
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return nil
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}
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for i := 0; i < len(e.resultChunks); i++ {
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remained := mathutil.Min(e.remainingRowsInChunk[i], remainingRowsInGroup)
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e.remainingRowsInChunk[i] -= remained
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remainingRowsInGroup -= remained
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// TODO: Combine these three methods.
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// The old implementation needs the processor has these three methods
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// but now it does not have to.
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groupRows, err = e.processor.consumeGroupRows(e.ctx, groupRows)
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if err != nil {
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return errors.Trace(err)
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}
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_, err = e.processor.appendResult2Chunk(e.ctx, groupRows, e.resultChunks[i], remained)
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if err != nil {
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return errors.Trace(err)
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}
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if remainingRowsInGroup == 0 {
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e.processor.resetPartialResult()
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break
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}
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}
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return nil
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}
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func (e *WindowExec) fetchChild(ctx context.Context) (EOF bool, err error) {
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childResult := newFirstChunk(e.children[0])
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err = Next(ctx, e.children[0], childResult)
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if err != nil {
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return false, errors.Trace(err)
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}
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// No more data.
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numRows := childResult.NumRows()
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if numRows == 0 {
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return true, nil
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}
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resultChk := chunk.New(e.retFieldTypes, 0, numRows)
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err = e.copyChk(childResult, resultChk)
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if err != nil {
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return false, err
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}
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e.resultChunks = append(e.resultChunks, resultChk)
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e.remainingRowsInChunk = append(e.remainingRowsInChunk, numRows)
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e.childResult = childResult
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return false, nil
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}
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func (e *WindowExec) copyChk(src, dst *chunk.Chunk) error {
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columns := e.Schema().Columns[:len(e.Schema().Columns)-e.numWindowFuncs]
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for i, col := range columns {
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if err := dst.MakeRefTo(i, src, col.Index); err != nil {
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return err
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}
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}
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return nil
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}
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// windowProcessor is the interface for processing different kinds of windows.
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type windowProcessor interface {
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// consumeGroupRows updates the result for an window function using the input rows
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// which belong to the same partition.
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consumeGroupRows(ctx sessionctx.Context, rows []chunk.Row) ([]chunk.Row, error)
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// appendResult2Chunk appends the final results to chunk.
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// It is called when there are no more rows in current partition.
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appendResult2Chunk(ctx sessionctx.Context, rows []chunk.Row, chk *chunk.Chunk, remained int) ([]chunk.Row, error)
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// resetPartialResult resets the partial result to the original state for a specific window function.
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resetPartialResult()
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}
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type aggWindowProcessor struct {
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windowFuncs []aggfuncs.AggFunc
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partialResults []aggfuncs.PartialResult
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}
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func (p *aggWindowProcessor) consumeGroupRows(ctx sessionctx.Context, rows []chunk.Row) ([]chunk.Row, error) {
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for i, windowFunc := range p.windowFuncs {
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err := windowFunc.UpdatePartialResult(ctx, rows, p.partialResults[i])
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if err != nil {
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return nil, err
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}
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}
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rows = rows[:0]
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return rows, nil
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}
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func (p *aggWindowProcessor) appendResult2Chunk(ctx sessionctx.Context, rows []chunk.Row, chk *chunk.Chunk, remained int) ([]chunk.Row, error) {
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for remained > 0 {
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for i, windowFunc := range p.windowFuncs {
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// TODO: We can extend the agg func interface to avoid the `for` loop here.
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err := windowFunc.AppendFinalResult2Chunk(ctx, p.partialResults[i], chk)
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if err != nil {
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return nil, err
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}
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}
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remained--
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}
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return rows, nil
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}
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func (p *aggWindowProcessor) resetPartialResult() {
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for i, windowFunc := range p.windowFuncs {
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windowFunc.ResetPartialResult(p.partialResults[i])
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}
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}
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type rowFrameWindowProcessor struct {
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windowFuncs []aggfuncs.AggFunc
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partialResults []aggfuncs.PartialResult
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start *core.FrameBound
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end *core.FrameBound
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curRowIdx uint64
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}
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func (p *rowFrameWindowProcessor) getStartOffset(numRows uint64) uint64 {
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if p.start.UnBounded {
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return 0
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}
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switch p.start.Type {
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case ast.Preceding:
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if p.curRowIdx >= p.start.Num {
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return p.curRowIdx - p.start.Num
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}
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return 0
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case ast.Following:
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offset := p.curRowIdx + p.start.Num
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if offset >= numRows {
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return numRows
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}
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return offset
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case ast.CurrentRow:
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return p.curRowIdx
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}
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// It will never reach here.
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return 0
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}
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func (p *rowFrameWindowProcessor) getEndOffset(numRows uint64) uint64 {
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if p.end.UnBounded {
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return numRows
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}
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switch p.end.Type {
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case ast.Preceding:
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if p.curRowIdx >= p.end.Num {
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return p.curRowIdx - p.end.Num + 1
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}
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return 0
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case ast.Following:
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offset := p.curRowIdx + p.end.Num
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if offset >= numRows {
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return numRows
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}
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return offset + 1
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case ast.CurrentRow:
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return p.curRowIdx + 1
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}
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// It will never reach here.
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return 0
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}
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func (p *rowFrameWindowProcessor) consumeGroupRows(ctx sessionctx.Context, rows []chunk.Row) ([]chunk.Row, error) {
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return rows, nil
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}
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func (p *rowFrameWindowProcessor) appendResult2Chunk(ctx sessionctx.Context, rows []chunk.Row, chk *chunk.Chunk, remained int) ([]chunk.Row, error) {
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numRows := uint64(len(rows))
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var (
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err error
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initializedSlidingWindow bool
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start uint64
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end uint64
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lastStart uint64
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lastEnd uint64
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shiftStart uint64
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shiftEnd uint64
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)
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slidingWindowAggFuncs := make([]aggfuncs.SlidingWindowAggFunc, len(p.windowFuncs))
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for i, windowFunc := range p.windowFuncs {
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if slidingWindowAggFunc, ok := windowFunc.(aggfuncs.SlidingWindowAggFunc); ok {
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slidingWindowAggFuncs[i] = slidingWindowAggFunc
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}
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}
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for ; remained > 0; lastStart, lastEnd = start, end {
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start = p.getStartOffset(numRows)
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end = p.getEndOffset(numRows)
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p.curRowIdx++
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remained--
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shiftStart = start - lastStart
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shiftEnd = end - lastEnd
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if start >= end {
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for i, windowFunc := range p.windowFuncs {
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slidingWindowAggFunc := slidingWindowAggFuncs[i]
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if slidingWindowAggFunc != nil && initializedSlidingWindow {
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err = slidingWindowAggFunc.Slide(ctx, rows, lastStart, lastEnd, shiftStart, shiftEnd, p.partialResults[i])
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if err != nil {
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return nil, err
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}
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}
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err = windowFunc.AppendFinalResult2Chunk(ctx, p.partialResults[i], chk)
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if err != nil {
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return nil, err
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}
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}
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continue
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}
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for i, windowFunc := range p.windowFuncs {
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slidingWindowAggFunc := slidingWindowAggFuncs[i]
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if slidingWindowAggFunc != nil && initializedSlidingWindow {
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err = slidingWindowAggFunc.Slide(ctx, rows, lastStart, lastEnd, shiftStart, shiftEnd, p.partialResults[i])
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} else {
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err = windowFunc.UpdatePartialResult(ctx, rows[start:end], p.partialResults[i])
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}
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if err != nil {
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return nil, err
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}
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err = windowFunc.AppendFinalResult2Chunk(ctx, p.partialResults[i], chk)
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if err != nil {
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return nil, err
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}
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if slidingWindowAggFunc == nil {
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windowFunc.ResetPartialResult(p.partialResults[i])
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}
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}
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if !initializedSlidingWindow {
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initializedSlidingWindow = true
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}
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}
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for i, windowFunc := range p.windowFuncs {
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windowFunc.ResetPartialResult(p.partialResults[i])
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}
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return rows, nil
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}
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func (p *rowFrameWindowProcessor) resetPartialResult() {
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p.curRowIdx = 0
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}
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type rangeFrameWindowProcessor struct {
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windowFuncs []aggfuncs.AggFunc
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partialResults []aggfuncs.PartialResult
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start *core.FrameBound
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end *core.FrameBound
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curRowIdx uint64
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lastStartOffset uint64
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lastEndOffset uint64
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orderByCols []*expression.Column
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// expectedCmpResult is used to decide if one value is included in the frame.
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expectedCmpResult int64
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}
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func (p *rangeFrameWindowProcessor) getStartOffset(ctx sessionctx.Context, rows []chunk.Row) (uint64, error) {
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if p.start.UnBounded {
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return 0, nil
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}
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numRows := uint64(len(rows))
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for ; p.lastStartOffset < numRows; p.lastStartOffset++ {
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var res int64
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var err error
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for i := range p.orderByCols {
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res, _, err = p.start.CmpFuncs[i](ctx, p.orderByCols[i], p.start.CalcFuncs[i], rows[p.lastStartOffset], rows[p.curRowIdx])
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if err != nil {
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return 0, err
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}
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if res != 0 {
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break
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}
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}
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// For asc, break when the current value is greater or equal to the calculated result;
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// For desc, break when the current value is less or equal to the calculated result.
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if res != p.expectedCmpResult {
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break
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}
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}
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return p.lastStartOffset, nil
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}
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func (p *rangeFrameWindowProcessor) getEndOffset(ctx sessionctx.Context, rows []chunk.Row) (uint64, error) {
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numRows := uint64(len(rows))
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if p.end.UnBounded {
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return numRows, nil
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}
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for ; p.lastEndOffset < numRows; p.lastEndOffset++ {
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var res int64
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var err error
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for i := range p.orderByCols {
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res, _, err = p.end.CmpFuncs[i](ctx, p.end.CalcFuncs[i], p.orderByCols[i], rows[p.curRowIdx], rows[p.lastEndOffset])
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if err != nil {
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return 0, err
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}
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if res != 0 {
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break
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}
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}
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// For asc, break when the calculated result is greater than the current value.
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// For desc, break when the calculated result is less than the current value.
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if res == p.expectedCmpResult {
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break
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}
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}
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return p.lastEndOffset, nil
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}
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func (p *rangeFrameWindowProcessor) appendResult2Chunk(ctx sessionctx.Context, rows []chunk.Row, chk *chunk.Chunk, remained int) ([]chunk.Row, error) {
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var (
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err error
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initializedSlidingWindow bool
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start uint64
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end uint64
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lastStart uint64
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lastEnd uint64
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shiftStart uint64
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shiftEnd uint64
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)
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slidingWindowAggFuncs := make([]aggfuncs.SlidingWindowAggFunc, len(p.windowFuncs))
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for i, windowFunc := range p.windowFuncs {
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if slidingWindowAggFunc, ok := windowFunc.(aggfuncs.SlidingWindowAggFunc); ok {
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slidingWindowAggFuncs[i] = slidingWindowAggFunc
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}
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}
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for ; remained > 0; lastStart, lastEnd = start, end {
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start, err = p.getStartOffset(ctx, rows)
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if err != nil {
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return nil, err
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}
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end, err = p.getEndOffset(ctx, rows)
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if err != nil {
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return nil, err
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}
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p.curRowIdx++
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remained--
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shiftStart = start - lastStart
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shiftEnd = end - lastEnd
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if start >= end {
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for i, windowFunc := range p.windowFuncs {
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slidingWindowAggFunc := slidingWindowAggFuncs[i]
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if slidingWindowAggFunc != nil && initializedSlidingWindow {
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err = slidingWindowAggFunc.Slide(ctx, rows, lastStart, lastEnd, shiftStart, shiftEnd, p.partialResults[i])
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if err != nil {
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return nil, err
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}
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}
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err = windowFunc.AppendFinalResult2Chunk(ctx, p.partialResults[i], chk)
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if err != nil {
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return nil, err
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}
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}
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continue
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}
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for i, windowFunc := range p.windowFuncs {
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slidingWindowAggFunc := slidingWindowAggFuncs[i]
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if slidingWindowAggFunc != nil && initializedSlidingWindow {
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err = slidingWindowAggFunc.Slide(ctx, rows, lastStart, lastEnd, shiftStart, shiftEnd, p.partialResults[i])
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} else {
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err = windowFunc.UpdatePartialResult(ctx, rows[start:end], p.partialResults[i])
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}
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if err != nil {
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return nil, err
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}
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err = windowFunc.AppendFinalResult2Chunk(ctx, p.partialResults[i], chk)
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if err != nil {
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return nil, err
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}
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if slidingWindowAggFunc == nil {
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windowFunc.ResetPartialResult(p.partialResults[i])
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}
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}
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if !initializedSlidingWindow {
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initializedSlidingWindow = true
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}
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}
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for i, windowFunc := range p.windowFuncs {
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windowFunc.ResetPartialResult(p.partialResults[i])
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}
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return rows, nil
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}
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func (p *rangeFrameWindowProcessor) consumeGroupRows(ctx sessionctx.Context, rows []chunk.Row) ([]chunk.Row, error) {
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return rows, nil
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}
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func (p *rangeFrameWindowProcessor) resetPartialResult() {
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p.curRowIdx = 0
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p.lastStartOffset = 0
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p.lastEndOffset = 0
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}
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