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planner/cascades: add transformation rule PushLimitDownUnionAll. #14264

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merged 6 commits into from
Dec 28, 2019
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planner/cascades: add transformation rule PushLimitDownUnionAll. #14264

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2ee2e27
Add transformation rule PushLimitDownUnionAll.
doggeral Dec 27, 2019
32274d9
Address comments.
doggeral Dec 27, 2019
689fa1a
Use groupExpr schema instead.
doggeral Dec 28, 2019
39522e8
Merge branch 'master' into master
doggeral Dec 28, 2019
78c471f
Merge branch 'master' into master
zz-jason Dec 28, 2019
3dea2f5
Merge branch 'master' into master
sre-bot Dec 28, 2019
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2 changes: 2 additions & 0 deletions planner/cascades/testdata/transformation_rules_suite_in.json
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Original file line number Diff line number Diff line change
Expand Up @@ -40,6 +40,8 @@
"select a, b, c from t t1 where t1.a in (select a from (select t2.a as a, t1.b as b from t t2 where t2.b > t1.b) x order by b limit 1)",
"select a, b from (select @i as a, @i := @i+1 as b from t) t order by a desc limit 1",
"(select a from t) union all (select b from t) order by a limit 2;",
"(select a from t) union all (select b from t) limit 2;",
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"(select a from t) union all (select b from t) limit 2 offset 5;",
"(select a from t) union all (select sum(a) from t where a > 2 group by b) order by a limit 2;",
"(select a from t) union all (select sum(a) from t where a > 2 group by b) order by a limit 1, 2;",
"(select a from t where a = 1) union all (select b from t where a = 2) union all (select c from t where a = 3) order by a limit 2;"
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94 changes: 94 additions & 0 deletions planner/cascades/testdata/transformation_rules_suite_out.json
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Original file line number Diff line number Diff line change
Expand Up @@ -576,6 +576,100 @@
" TableScan_24 table:t"
]
},
{
"SQL": "(select a from t) union all (select b from t) limit 2;",
"Result": [
"Group#0 Schema:[Column#25]",
" Limit_8 input:[Group#1], offset:0, count:2",
"Group#1 Schema:[Column#25]",
" Union_5 input:[Group#2,Group#3]",
"Group#2 Schema:[Column#25]",
" Projection_6 input:[Group#4], test.t.a",
"Group#4 Schema:[test.t.a]",
" Projection_4 input:[Group#5], test.t.a",
"Group#5 Schema:[test.t.a]",
" Limit_25 input:[Group#6], offset:0, count:2",
"Group#6 Schema:[test.t.a]",
" TiKVSingleGather_10 input:[Group#7], table:t",
" TiKVSingleGather_22 input:[Group#8], table:t, index:e_d_c_str_prefix",
" TiKVSingleGather_20 input:[Group#9], table:t, index:c_d_e_str",
" TiKVSingleGather_18 input:[Group#10], table:t, index:f_g",
" TiKVSingleGather_16 input:[Group#11], table:t, index:g",
" TiKVSingleGather_14 input:[Group#12], table:t, index:f",
" TiKVSingleGather_12 input:[Group#13], table:t, index:c_d_e",
"Group#7 Schema:[test.t.a]",
" TableScan_9 table:t, pk col:test.t.a",
"Group#8 Schema:[test.t.a]",
" IndexScan_21 table:t, index:e_str, d_str, c_str",
"Group#9 Schema:[test.t.a]",
" IndexScan_19 table:t, index:c_str, d_str, e_str",
"Group#10 Schema:[test.t.a]",
" IndexScan_17 table:t, index:f, g",
"Group#11 Schema:[test.t.a]",
" IndexScan_15 table:t, index:g",
"Group#12 Schema:[test.t.a]",
" IndexScan_13 table:t, index:f",
"Group#13 Schema:[test.t.a]",
" IndexScan_11 table:t, index:c, d, e",
"Group#3 Schema:[Column#25]",
" Projection_7 input:[Group#14], test.t.b",
"Group#14 Schema:[test.t.b]",
" Projection_2 input:[Group#15], test.t.b",
"Group#15 Schema:[test.t.b]",
" Limit_25 input:[Group#16], offset:0, count:2",
"Group#16 Schema:[test.t.b]",
" TiKVSingleGather_24 input:[Group#17], table:t",
"Group#17 Schema:[test.t.b]",
" TableScan_23 table:t"
]
},
{
"SQL": "(select a from t) union all (select b from t) limit 2 offset 5;",
"Result": [
"Group#0 Schema:[Column#25]",
" Limit_8 input:[Group#1], offset:5, count:2",
"Group#1 Schema:[Column#25]",
" Union_5 input:[Group#2,Group#3]",
"Group#2 Schema:[Column#25]",
" Projection_6 input:[Group#4], test.t.a",
"Group#4 Schema:[test.t.a]",
" Projection_4 input:[Group#5], test.t.a",
"Group#5 Schema:[test.t.a]",
" Limit_25 input:[Group#6], offset:0, count:7",
"Group#6 Schema:[test.t.a]",
" TiKVSingleGather_10 input:[Group#7], table:t",
" TiKVSingleGather_22 input:[Group#8], table:t, index:e_d_c_str_prefix",
" TiKVSingleGather_20 input:[Group#9], table:t, index:c_d_e_str",
" TiKVSingleGather_18 input:[Group#10], table:t, index:f_g",
" TiKVSingleGather_16 input:[Group#11], table:t, index:g",
" TiKVSingleGather_14 input:[Group#12], table:t, index:f",
" TiKVSingleGather_12 input:[Group#13], table:t, index:c_d_e",
"Group#7 Schema:[test.t.a]",
" TableScan_9 table:t, pk col:test.t.a",
"Group#8 Schema:[test.t.a]",
" IndexScan_21 table:t, index:e_str, d_str, c_str",
"Group#9 Schema:[test.t.a]",
" IndexScan_19 table:t, index:c_str, d_str, e_str",
"Group#10 Schema:[test.t.a]",
" IndexScan_17 table:t, index:f, g",
"Group#11 Schema:[test.t.a]",
" IndexScan_15 table:t, index:g",
"Group#12 Schema:[test.t.a]",
" IndexScan_13 table:t, index:f",
"Group#13 Schema:[test.t.a]",
" IndexScan_11 table:t, index:c, d, e",
"Group#3 Schema:[Column#25]",
" Projection_7 input:[Group#14], test.t.b",
"Group#14 Schema:[test.t.b]",
" Projection_2 input:[Group#15], test.t.b",
"Group#15 Schema:[test.t.b]",
" Limit_25 input:[Group#16], offset:0, count:7",
"Group#16 Schema:[test.t.b]",
" TiKVSingleGather_24 input:[Group#17], table:t",
"Group#17 Schema:[test.t.b]",
" TableScan_23 table:t"
]
},
{
"SQL": "(select a from t) union all (select sum(a) from t where a > 2 group by b) order by a limit 2;",
"Result": [
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51 changes: 51 additions & 0 deletions planner/cascades/transformation_rules.go
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Original file line number Diff line number Diff line change
Expand Up @@ -65,6 +65,7 @@ var defaultTransformationMap = map[memo.Operand][]Transformation{
memo.OperandLimit: {
NewRuleTransformLimitToTopN(),
NewRulePushLimitDownProjection(),
NewRulePushLimitDownUnionAll(),
},
memo.OperandProjection: {
NewRuleEliminateProjection(),
Expand Down Expand Up @@ -710,6 +711,56 @@ func (r *PushLimitDownProjection) OnTransform(old *memo.ExprIter) (newExprs []*m
return []*memo.GroupExpr{projExpr}, true, false, nil
}

// PushLimitDownUnionAll pushes limit to union all.
type PushLimitDownUnionAll struct {
baseRule
}

// NewRulePushLimitDownUnionAll creates a new Transformation PushLimitDownUnionAll.
// The pattern of this rule is `Limit->UnionAll->X`.
func NewRulePushLimitDownUnionAll() Transformation {
rule := &PushLimitDownUnionAll{}
rule.pattern = memo.BuildPattern(
memo.OperandLimit,
memo.EngineTiDBOnly,
memo.NewPattern(memo.OperandUnionAll, memo.EngineTiDBOnly),
)
return rule
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}

// Match implements Transformation interface.
// Use appliedRuleSet in GroupExpr to avoid re-apply rules.
func (r *PushLimitDownUnionAll) Match(expr *memo.ExprIter) bool {
return !expr.GetExpr().HasAppliedRule(r)
}

// OnTransform implements Transformation interface.
// It will transform `Limit->UnionAll->X` to `Limit->UnionAll->Limit->X`.
func (r *PushLimitDownUnionAll) OnTransform(old *memo.ExprIter) (newExprs []*memo.GroupExpr, eraseOld bool, eraseAll bool, err error) {
limit := old.GetExpr().ExprNode.(*plannercore.LogicalLimit)
unionAll := old.Children[0].GetExpr().ExprNode.(*plannercore.LogicalUnionAll)
unionAllSchema := old.Children[0].Group.Prop.Schema

newLimit := plannercore.LogicalLimit{
Count: limit.Count + limit.Offset,
}.Init(limit.SCtx(), limit.SelectBlockOffset())

newUnionAllExpr := memo.NewGroupExpr(unionAll)
for _, childGroup := range old.Children[0].GetExpr().Children {
newLimitExpr := memo.NewGroupExpr(newLimit)
newLimitExpr.Children = append(newLimitExpr.Children, childGroup)
newLimitGroup := memo.NewGroupWithSchema(newLimitExpr, childGroup.Prop.Schema)

newUnionAllExpr.Children = append(newUnionAllExpr.Children, newLimitGroup)
}

newLimitExpr := memo.NewGroupExpr(limit)
newUnionAllGroup := memo.NewGroupWithSchema(newUnionAllExpr, unionAllSchema)
newLimitExpr.SetChildren(newUnionAllGroup)
newLimitExpr.AddAppliedRule(r)
return []*memo.GroupExpr{newLimitExpr}, true, false, nil
}

// PushSelDownJoin pushes Selection through Join.
type PushSelDownJoin struct {
baseRule
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1 change: 1 addition & 0 deletions planner/cascades/transformation_rules_test.go
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Original file line number Diff line number Diff line change
Expand Up @@ -150,6 +150,7 @@ func (s *testTransformationRuleSuite) TestTopNRules(c *C) {
memo.OperandLimit: {
NewRuleTransformLimitToTopN(),
NewRulePushLimitDownProjection(),
NewRulePushLimitDownUnionAll(),
},
memo.OperandDataSource: {
NewRuleEnumeratePaths(),
Expand Down