Plotting ibis.table converts to pyarrow twice

[MarcoGorelli]

What happened?

import polars as pl
import altair as alt

import ibis
ibis.set_backend('polars')

df = pl.DataFrame({'a': [1,2,3], 'b': [4,5,6]})
tbl = ibis.memtable(df)

alt.Chart(tbl).mark_point().encode(x='a', y='b').to_json()

If I put a breakpoint in arrow_table_from_dfi_dataframe, then I see the conversion from ibis table to arrow table happening twice

What would you like to happen instead?

I think it should be possible to convert at most once?

Which version of Altair are you using?

5.4.0dev (latest commit on main)

[MarcoGorelli]

Ah my mistake here, it's only doing one conversion - the second time it hits that breakpoint, dfi_df is a PyArrow table, and so the from_dataframe call is practically a no-op:

https://github.com/apache/arrow/blob/718415030f8ebcad14bc3fa10906beca6526c5e9/python/pyarrow/interchange/from_dataframe.py#L63-L106

Closing then, sorry for the noise