Eliminate OFFSET 0 in the logical plan optimization #3355
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❯ create view v as select 1 as a, 2 as b, 3 as c;
0 rows in set. Query took 0.010 seconds.
❯ explain select * from v offset 0 limit 2;
+---------------+-------------------------------------------------------+
| plan_type | plan |
+---------------+-------------------------------------------------------+
| logical_plan | Limit: skip=0, fetch=2 |
| | Projection: #v.a, #v.b, #v.c |
| | TableScan: v projection=[a, b, c], fetch=2 |
| physical_plan | GlobalLimitExec: skip=0, fetch=2 |
| | ProjectionExec: expr=[a@0 as a, b@1 as b, c@2 as c] |
| | ProjectionExec: expr=[1 as a, 2 as b, 3 as c] |
| | EmptyExec: produce_one_row=true |
| | |
+---------------+-------------------------------------------------------+
❯ explain select * from v limit 2;
+---------------+-------------------------------------------------------+
| plan_type | plan |
+---------------+-------------------------------------------------------+
| logical_plan | Limit: skip=None, fetch=2 |
| | Projection: #v.a, #v.b, #v.c |
| | TableScan: v projection=[a, b, c], fetch=2 |
| physical_plan | GlobalLimitExec: skip=None, fetch=2 |
| | ProjectionExec: expr=[a@0 as a, b@1 as b, c@2 as c] |
| | ProjectionExec: expr=[1 as a, 2 as b, 3 as c] |
| | EmptyExec: produce_one_row=true |
| | |
+---------------+-------------------------------------------------------+
I'd like explain select * from v offset 0 limit 2 and explain select * from v limit 2; to have same logical plan.
Also, in eliminate_limit.rs, we should eliminate the Limit plan when fetch = None and skip = 0 or skip = None.
https://github.com/apache/arrow-datafusion/blob/master/datafusion/optimizer/src/eliminate_limit.rs#L75-L91
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