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planner: when pushing topN down below proj, check whether topN.ByItems contains a column(with ID=0) generated by proj (#40593) #41178

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merged 10 commits into from
Aug 17, 2023
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planner: when pushing topN down below proj, check whether topN.ByItems contains a column(with ID=0) generated by proj (#40593) #41178

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b76f793
the proj below sort will prevent optimizer from pushing the proj down…
Dousir9 Jan 14, 2023
f948c02
add unit test
Dousir9 Jan 14, 2023
26a284a
fix-typo
Dousir9 Jan 14, 2023
33a4fd9
put the test case into the existing file.
Dousir9 Jan 16, 2023
3cb0ee0
check whether proj can be eliminated or contains a column in topN.ByI…
Dousir9 Jan 17, 2023
b78cc3f
remove unnecessary check
Dousir9 Jan 17, 2023
4f0ce38
change the code of LogicalProjection.pushDownTopN instead of the Logi…
Dousir9 Jan 19, 2023
c3d61bb
fix: with Column.ID = 0
Dousir9 Jan 30, 2023
3aa0278
check whether the column is generated by projection
Dousir9 Jan 30, 2023
1a938d5
update comment
Dousir9 Jan 30, 2023
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13 changes: 13 additions & 0 deletions planner/core/plan_test.go
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Original file line number Diff line number Diff line change
Expand Up @@ -25,6 +25,7 @@ import (
"github.com/pingcap/tidb/config"
"github.com/pingcap/tidb/expression"
"github.com/pingcap/tidb/expression/aggregation"
"github.com/pingcap/tidb/kv"
"github.com/pingcap/tidb/parser/ast"
"github.com/pingcap/tidb/parser/model"
"github.com/pingcap/tidb/parser/mysql"
Expand Down Expand Up @@ -1140,3 +1141,15 @@ func TestJSONPlanInExplain(t *testing.T) {
}
}
}

func TestIssue40535(t *testing.T) {
store := testkit.CreateMockStore(t)
var cfg kv.InjectionConfig
tk := testkit.NewTestKit(t, kv.NewInjectedStore(store, &cfg))
tk.MustExec("use test;")
tk.MustExec("drop table if exists t1; drop table if exists t2;")
tk.MustExec("CREATE TABLE `t1`(`c1` bigint(20) NOT NULL DEFAULT '-2312745469307452950', `c2` datetime DEFAULT '5316-02-03 06:54:49', `c3` tinyblob DEFAULT NULL, PRIMARY KEY (`c1`) /*T![clustered_index] CLUSTERED */) ENGINE=InnoDB DEFAULT CHARSET=utf8 COLLATE=utf8_bin;")
tk.MustExec("CREATE TABLE `t2`(`c1` set('kn8pu','7et','vekx6','v3','liwrh','q14','1met','nnd5i','5o0','8cz','l') DEFAULT '7et,vekx6,liwrh,q14,1met', `c2` float DEFAULT '1.683167', KEY `k1` (`c2`,`c1`), KEY `k2` (`c2`)) ENGINE=InnoDB DEFAULT CHARSET=gbk COLLATE=gbk_chinese_ci;")
tk.MustExec("(select /*+ agg_to_cop()*/ locate(t1.c3, t1.c3) as r0, t1.c3 as r1 from t1 where not( IsNull(t1.c1)) order by r0,r1) union all (select concat_ws(',', t2.c2, t2.c1) as r0, t2.c1 as r1 from t2 order by r0, r1) order by 1 limit 273;")
require.Empty(t, tk.Session().LastMessage())
}
14 changes: 14 additions & 0 deletions planner/core/rule_topn_push_down.go
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Original file line number Diff line number Diff line change
Expand Up @@ -136,6 +136,20 @@ func (p *LogicalProjection) pushDownTopN(topN *LogicalTopN, opt *logicalOptimize
topN.ByItems = append(topN.ByItems[:i], topN.ByItems[i+1:]...)
}
}

// if topN.ByItems contains a column(with ID=0) generated by projection, projection will prevent the optimizer from pushing topN down.
for _, by := range topN.ByItems {
cols := expression.ExtractColumns(by.Expr)
for _, col := range cols {
if col.ID == 0 && p.Schema().Contains(col) {
// check whether the column is generated by projection
if !p.children[0].Schema().Contains(col) {
p.children[0] = p.children[0].pushDownTopN(nil, opt)
return topN.setChild(p, opt)
}
}
}
}
}
p.children[0] = p.children[0].pushDownTopN(topN, opt)
return p
Expand Down