alamb opened a new issue #417:
URL: https://github.com/apache/arrow-datafusion/issues/417
**Is your feature request related to a problem or challenge? Please describe
what you are trying to do.**
When pushing predicates down into various storage systems, it is common for
them to support single column predicates of the form
```
const OP column
```
SQL allows users to write predicates against columns using whatever format
they deem useful, and inserts the appropriate `CAST` functions where needed.
However
```
echo "1" > /tmp/foo.csv
cargo run -p datafusion-cli
```
And then run:
```
> CREATE EXTERNAL TABLE foo(ts double)
STORED AS CSV
LOCATION '/tmp/foo.csv';
0 rows in set. Query took 0 seconds.
> explain verbose select * from foo where ts < 5;
+-----------------------------------------+--------------------------------------------------------------------------+
| plan_type | plan
|
+-----------------------------------------+--------------------------------------------------------------------------+
| logical_plan | Projection: #ts
|
| | Filter: #ts Lt Int64(5)
|
| | TableScan: foo
projection=None |
| logical_plan after projection_push_down | Projection: #ts
|
| | Filter: #ts Lt Int64(5)
|
| | TableScan: foo
projection=Some([0]) |
| logical_plan after projection_push_down | Projection: #ts
|
| | Filter: #ts Lt Int64(5)
|
| | TableScan: foo
projection=Some([0]) |
| physical_plan | ProjectionExec: expr=[ts]
|
| | FilterExec: ts < CAST(5 AS
Float64) |
| | CsvExec:
source=Path(/tmp/foo.csv: [/tmp/foo.csv]), has_header=false |
+-----------------------------------------+--------------------------------------------------------------------------+
4 rows in set. Query took 0 seconds.
```
You can see that the filter that was pushed down was `ts < CAST(5 AS
Float64) ` which is correct, but it will likely not be recognized by some
storage systems (such as IOx).
**Describe the solution you'd like**
What I would like to see is the expression rewriter pass rewrite `ts <
CAST(5 AS Float64)` into `ts < 5.0` (aka do the cast at plan time)
--
This is an automated message from the Apache Git Service.
To respond to the message, please log on to GitHub and use the
URL above to go to the specific comment.
For queries about this service, please contact Infrastructure at:
[email protected]
