// Copyright 2019 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 aggfuncs import ( "github.com/pingcap/tidb/expression" "github.com/pingcap/tidb/sessionctx" "github.com/pingcap/tidb/util/chunk" ) type baseLeadLag struct { baseAggFunc valueEvaluator // TODO: move it to partial result when parallel execution is supported. defaultExpr expression.Expression offset uint64 } type partialResult4LeadLag struct { rows []chunk.Row curIdx uint64 } func (v *baseLeadLag) AllocPartialResult() PartialResult { return PartialResult(&partialResult4LeadLag{}) } func (v *baseLeadLag) ResetPartialResult(pr PartialResult) { p := (*partialResult4LeadLag)(pr) p.rows = p.rows[:0] p.curIdx = 0 } func (v *baseLeadLag) UpdatePartialResult(sctx sessionctx.Context, rowsInGroup []chunk.Row, pr PartialResult) error { p := (*partialResult4LeadLag)(pr) p.rows = append(p.rows, rowsInGroup...) return nil } type lead struct { baseLeadLag } func (v *lead) AppendFinalResult2Chunk(sctx sessionctx.Context, pr PartialResult, chk *chunk.Chunk) error { p := (*partialResult4LeadLag)(pr) var err error if p.curIdx+v.offset < uint64(len(p.rows)) { err = v.evaluateRow(sctx, v.args[0], p.rows[p.curIdx+v.offset]) } else { err = v.evaluateRow(sctx, v.defaultExpr, p.rows[p.curIdx]) } if err != nil { return err } v.appendResult(chk, v.ordinal) p.curIdx++ return nil } type lag struct { baseLeadLag } func (v *lag) AppendFinalResult2Chunk(sctx sessionctx.Context, pr PartialResult, chk *chunk.Chunk) error { p := (*partialResult4LeadLag)(pr) var err error if p.curIdx >= v.offset { err = v.evaluateRow(sctx, v.args[0], p.rows[p.curIdx-v.offset]) } else { err = v.evaluateRow(sctx, v.defaultExpr, p.rows[p.curIdx]) } if err != nil { return err } v.appendResult(chk, v.ordinal) p.curIdx++ return nil }