52 lines
2.1 KiB
Go
52 lines
2.1 KiB
Go
// Copyright 2023 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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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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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 cardinality
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import (
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"math"
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"github.com/pingcap/tidb/pkg/expression"
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"github.com/pingcap/tidb/pkg/planner/planctx"
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"github.com/pingcap/tidb/pkg/planner/property"
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)
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// EstimateFullJoinRowCount estimates the row count of a full join.
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func EstimateFullJoinRowCount(sctx planctx.PlanContext,
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isCartesian bool,
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leftProfile, rightProfile *property.StatsInfo,
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leftJoinKeys, rightJoinKeys []*expression.Column,
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leftSchema, rightSchema *expression.Schema,
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leftNAJoinKeys, rightNAJoinKeys []*expression.Column) float64 {
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if isCartesian {
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return leftProfile.RowCount * rightProfile.RowCount
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}
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var leftKeyNDV, rightKeyNDV float64
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var leftColCnt, rightColCnt int
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if len(leftJoinKeys) > 0 || len(rightJoinKeys) > 0 {
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leftKeyNDV, leftColCnt = EstimateColsNDVWithMatchedLen(leftJoinKeys, leftSchema, leftProfile)
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rightKeyNDV, rightColCnt = EstimateColsNDVWithMatchedLen(rightJoinKeys, rightSchema, rightProfile)
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} else {
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leftKeyNDV, leftColCnt = EstimateColsNDVWithMatchedLen(leftNAJoinKeys, leftSchema, leftProfile)
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rightKeyNDV, rightColCnt = EstimateColsNDVWithMatchedLen(rightNAJoinKeys, rightSchema, rightProfile)
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}
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count := leftProfile.RowCount * rightProfile.RowCount / max(leftKeyNDV, rightKeyNDV)
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if sctx.GetSessionVars().TiDBOptJoinReorderThreshold <= 0 {
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return count
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}
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// If we enable the DP choice, we multiple the 0.9 for each remained join key supposing that 0.9 is the correlation factor between them.
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// This estimation logic is referred to Presto.
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return count * math.Pow(0.9, float64(len(leftJoinKeys)-max(leftColCnt, rightColCnt)))
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}
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