github.com/whtcorpsinc/milevadb-prod@v0.0.0-20211104133533-f57f4be3b597/dbs/cmd/benchdb/explaintest/r/topn_pushdown.result (about)

     1  explain select * from ((select 4 as a) union all (select 33 as a)) tmp order by a desc limit 1;
     2  id	estRows	task	access object	operator info
     3  TopN_17	1.00	root		DeferredCauset#3:desc, offset:0, count:1
     4  └─Union_21	2.00	root		
     5    ├─Projection_22	1.00	root		4->DeferredCauset#3
     6    │ └─TableDual_23	1.00	root		rows:1
     7    └─Projection_24	1.00	root		33->DeferredCauset#3
     8      └─TableDual_25	1.00	root		rows:1