apache / apache/datafusion-python

Create more user friendly aliases from `col`

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#754 5 bình luận 3 reaction 0 người được giao Xem trên GitHub
enhancement
Ngôn ngữ chính
Python
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Mô tả

**Is your feature request related to a problem or challenge? Please describe what you are trying to do.**
This is a user enhancement request to make the python interface remove the default `?table?` on columns.

**Describe the solution you'd like**
I have not yet reviewed the applicable code to offer a best solution yet. I'm adding this feature request to track.

**Describe alternatives you've considered**
User adds an `.alias()` command as below, which may be tedious.

**Additional context**
See the below example from @datapythonista that includes the desired use case

```
import datafusion
from datafusion import col, lit, functions as f
import pyarrow

# something like this would be implemented internally, so users can call `datafusion.read_*`
def _read_parquet(*args, **kwargs):
ctx = datafusion.SessionContext()
return ctx.read_parquet(*args, **kwargs)
datafusion.read_parquet = _read_parquet # creating an alias of `read_*` functions so users don't need to know about `SessionContext` when the defaults are fine

df = (datafusion.read_parquet("buildings.parquet")
.filter( # `.filter()` accepting multiple conditions (which will be an AND) instead of having to use `&` with its operator precedence problems
col("is_offplan") == False,
col("rooms") >= 2, # `.lit(2)` not being required, and Python literals working with operators
)
.aggregate(
[col("area_name_en")],
[f.mean(col("has_parking").cast(float))], # `.cast()` accepting Python types, which would be internally converted to the PyArrow equivalent
)
.select(
col("area_name_en").alias("Area"),
col("AVG(has_parking)").alias("Percentage of buildings with parking"), # removing the default `?table?` in column names, the column name was "AVG(?table?.has_parking)"
)
)
```

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