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89 lines
2.2 KiB
89 lines
2.2 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 aggfuncs
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import (
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"github.com/pingcap/tidb/expression"
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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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type baseLeadLag struct {
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baseAggFunc
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valueEvaluator // TODO: move it to partial result when parallel execution is supported.
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defaultExpr expression.Expression
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offset uint64
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}
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type partialResult4LeadLag struct {
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rows []chunk.Row
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curIdx uint64
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}
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func (v *baseLeadLag) AllocPartialResult() PartialResult {
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return PartialResult(&partialResult4LeadLag{})
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}
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func (v *baseLeadLag) ResetPartialResult(pr PartialResult) {
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p := (*partialResult4LeadLag)(pr)
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p.rows = p.rows[:0]
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p.curIdx = 0
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}
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func (v *baseLeadLag) UpdatePartialResult(sctx sessionctx.Context, rowsInGroup []chunk.Row, pr PartialResult) error {
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p := (*partialResult4LeadLag)(pr)
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p.rows = append(p.rows, rowsInGroup...)
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return nil
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}
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type lead struct {
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baseLeadLag
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}
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func (v *lead) AppendFinalResult2Chunk(sctx sessionctx.Context, pr PartialResult, chk *chunk.Chunk) error {
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p := (*partialResult4LeadLag)(pr)
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var err error
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if p.curIdx+v.offset < uint64(len(p.rows)) {
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err = v.evaluateRow(sctx, v.args[0], p.rows[p.curIdx+v.offset])
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} else {
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err = v.evaluateRow(sctx, v.defaultExpr, p.rows[p.curIdx])
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}
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if err != nil {
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return err
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}
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v.appendResult(chk, v.ordinal)
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p.curIdx++
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return nil
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}
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type lag struct {
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baseLeadLag
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}
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func (v *lag) AppendFinalResult2Chunk(sctx sessionctx.Context, pr PartialResult, chk *chunk.Chunk) error {
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p := (*partialResult4LeadLag)(pr)
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var err error
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if p.curIdx >= v.offset {
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err = v.evaluateRow(sctx, v.args[0], p.rows[p.curIdx-v.offset])
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} else {
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err = v.evaluateRow(sctx, v.defaultExpr, p.rows[p.curIdx])
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}
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if err != nil {
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return err
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}
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v.appendResult(chk, v.ordinal)
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p.curIdx++
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return nil
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}
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