zhuqi-lucas commented on code in PR #14418:
URL: https://github.com/apache/datafusion/pull/14418#discussion_r1940630342
##########
datafusion/physical-optimizer/src/limit_pushdown.rs:
##########
@@ -146,6 +146,15 @@ pub fn pushdown_limit_helper(
global_state.skip = skip;
global_state.fetch = fetch;
+ if limit_exec.input().as_any().is::<CoalescePartitionsExec>() {
Review Comment:
Updated, i confirmed SortPreservingMerge works well with fetch:
```rust
# Check output plan, expect no "output_ordering" clause in the physical_plan
-> ParquetExec:
query TT
explain with selection as (
select *
from test_table
ORDER BY string_col, int_col limit 1
)
select 1 as foo
from selection
order by string_col
limit 1000;
----
logical_plan
01)Projection: foo
02)--Sort: selection.string_col ASC NULLS LAST, fetch=1000
03)----Projection: Int64(1) AS foo, selection.string_col
04)------SubqueryAlias: selection
05)--------Projection: test_table.string_col
06)----------Sort: test_table.string_col ASC NULLS LAST, test_table.int_col
ASC NULLS LAST, fetch=1
07)------------TableScan: test_table projection=[int_col, string_col]
physical_plan
01)ProjectionExec: expr=[foo@0 as foo]
02)--ProjectionExec: expr=[1 as foo, string_col@0 as string_col]
03)----ProjectionExec: expr=[string_col@1 as string_col]
04)------SortPreservingMergeExec: [string_col@1 ASC NULLS LAST, int_col@0
ASC NULLS LAST], fetch=1
05)--------SortExec: TopK(fetch=1), expr=[string_col@1 ASC NULLS LAST,
int_col@0 ASC NULLS LAST], preserve_partitioning=[true]
06)----------ParquetExec: file_groups={2 groups:
[[WORKSPACE_ROOT/datafusion/sqllogictest/test_files/scratch/parquet/test_table/0.parquet],
[WORKSPACE_ROOT/datafusion/sqllogictest/test_files/scratch/parquet/test_table/1.parquet]]},
projection=[int_col, string_col]
```
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