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dd377dedaa
* add coprocessor support Signed-off-by: Connor1996 <zbk602423539@gmail.com> Co-authored-by: Yiding Cui <winoros@gmail.com>
140 lines
3.1 KiB
Go
140 lines
3.1 KiB
Go
// Copyright 2019-present 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 coprocessor
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import (
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"container/heap"
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"github.com/juju/errors"
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"github.com/pingcap/tidb/sessionctx/stmtctx"
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"github.com/pingcap/tidb/types"
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tipb "github.com/pingcap/tipb/go-tipb"
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)
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type sortRow struct {
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key []types.Datum
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data [][]byte
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}
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// topNSorter implements sort.Interface. When all rows have been processed, the topNSorter will sort the whole data in heap.
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type topNSorter struct {
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orderByItems []*tipb.ByItem
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rows []*sortRow
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err error
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sc *stmtctx.StatementContext
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}
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func (t *topNSorter) Len() int {
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return len(t.rows)
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}
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func (t *topNSorter) Swap(i, j int) {
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t.rows[i], t.rows[j] = t.rows[j], t.rows[i]
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}
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func (t *topNSorter) Less(i, j int) bool {
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for index, by := range t.orderByItems {
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v1 := t.rows[i].key[index]
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v2 := t.rows[j].key[index]
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ret, err := v1.CompareDatum(t.sc, &v2)
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if err != nil {
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t.err = errors.Trace(err)
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return true
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}
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if by.Desc {
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ret = -ret
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}
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if ret < 0 {
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return true
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} else if ret > 0 {
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return false
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}
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}
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return false
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}
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// topNHeap holds the top n elements using heap structure. It implements heap.Interface.
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// When we insert a row, topNHeap will check if the row can become one of the top n element or not.
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type topNHeap struct {
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topNSorter
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// totalCount is equal to the limit count, which means the max size of heap.
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totalCount int
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// heapSize means the current size of this heap.
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heapSize int
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}
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func (t *topNHeap) Len() int {
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return t.heapSize
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}
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func (t *topNHeap) Push(x interface{}) {
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t.rows = append(t.rows, x.(*sortRow))
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t.heapSize++
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}
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func (t *topNHeap) Pop() interface{} {
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return nil
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}
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func (t *topNHeap) Less(i, j int) bool {
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for index, by := range t.orderByItems {
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v1 := t.rows[i].key[index]
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v2 := t.rows[j].key[index]
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ret, err := v1.CompareDatum(t.sc, &v2)
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if err != nil {
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t.err = errors.Trace(err)
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return true
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}
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if by.Desc {
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ret = -ret
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}
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if ret > 0 {
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return true
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} else if ret < 0 {
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return false
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}
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}
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return false
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}
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// tryToAddRow tries to add a row to heap.
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// When this row is not less than any rows in heap, it will never become the top n element.
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// Then this function returns false.
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func (t *topNHeap) tryToAddRow(row *sortRow) bool {
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success := false
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if t.heapSize == t.totalCount {
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t.rows = append(t.rows, row)
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// When this row is less than the top element, it will replace it and adjust the heap structure.
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if t.Less(0, t.heapSize) {
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t.Swap(0, t.heapSize)
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heap.Fix(t, 0)
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success = true
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}
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t.rows = t.rows[:t.heapSize]
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} else {
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heap.Push(t, row)
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success = true
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}
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return success
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}
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