Kartothek metadata does not distinguish int64 and Int64

[mlondschien]

In [1]: from functools import partial
   ...: 
   ...: import pandas as pd
   ...: import storefact
   ...: from kartothek.core.common_metadata import empty_dataframe_from_schema
   ...: from kartothek.io.dask.dataframe import read_dataset_as_ddf
   ...: from kartothek.io.eager import read_table, store_dataframes_as_dataset
   ...: 
   ...: store = partial(storefact.get_store_from_url, "hfs:///tmp")
   ...: 
   ...: df = pd.DataFrame(
   ...:     {
   ...:         "i": [0, 1],
   ...:         "I": [0, pd.NA],
   ...:         "o": ["a", None],
   ...:         "s": ["b", pd.NA],
   ...:         "b": [True, False],
   ...:         "B": [True, pd.NA],
   ...:     }
   ...: )
   ...: df["I"] = df["I"].astype("Int64")
   ...: df["s"] = df["s"].astype("string")
   ...: df["B"] = df["B"].astype("boolean")
   ...: 
   ...: df.dtypes
Out[1]: 
i      int64
I      Int64
o     object
s     string
b       bool
B    boolean
dtype: object

In [2]: dm = store_dataframes_as_dataset(
   ...:     dfs=[df], dataset_uuid="dataset", store=store, overwrite=True
   ...: )
   ...: 
   ...: df_meta = empty_dataframe_from_schema(schema=dm.table_meta["table"])
   ...: df_meta.dtypes
Out[2]: 
B    boolean
I      int64
b       bool
i      int64
o     object
s     string
dtype: object

In [3]: ddf = read_dataset_as_ddf(dataset_uuid="dataset", store=store)
   ...: ddf._meta.dtypes
Out[3]: 
B    boolean
I      int64
b       bool
i      int64
o     object
s     string
dtype: object

In [4]: ddf.compute().dtypes
Out[4]: 
B    boolean
I      Int64
b       bool
i      int64
o     object
s     string
dtype: object

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Details

from functools import partial

import pandas as pd
import storefact
from kartothek.core.common_metadata import empty_dataframe_from_schema
from kartothek.io.dask.dataframe import read_dataset_as_ddf
from kartothek.io.eager import read_table, store_dataframes_as_dataset

store = partial(storefact.get_store_from_url, "hfs:///tmp")

df = pd.DataFrame(
    {
        "i": [0, 1],
        "I": [0, pd.NA],
        "o": ["a", None],
        "s": ["b", pd.NA],
        "b": [True, False],
        "B": [True, pd.NA],
    }
)
df["I"] = df["I"].astype("Int64")
df["s"] = df["s"].astype("string")
df["B"] = df["B"].astype("boolean")

df.dtypes

dm = store_dataframes_as_dataset(
    dfs=[df], dataset_uuid="dataset", store=store, overwrite=True
)

df_meta = empty_dataframe_from_schema(schema=dm.table_meta["table"])
df_meta.dtypes

ddf = read_dataset_as_ddf(dataset_uuid="dataset", store=store)
ddf._meta.dtypes

ddf.compute().dtypes

The dtype is incorrectly stored in the kartothek metadata:

In [12]: store().get(dataset/table/_common_metadata)
Out[12]: b'PAR1\x15\x04\x19|5\x00\x18\x06schema\x15\x0c\x00\x15\x00%\x02\x18\x01B\x00\x15\x04%\x02\x18\x01I\x00\x15\x00%\x02\x18\x01b\x00\x15\x04%\x02\x18\x01i\x00\x15\x0c%\x02\x18\x01o%\x00L\x1c\x00\x00\x00\x15\x0c%\x02\x18\x01s%\x00L\x1c\x00\x00\x00\x16\x00\x19\x0c\x19,\x18\x06pandas\x18\x99\x07{"column_indexes": [{"field_name": null, "metadata": {"encoding": "UTF-8"}, "name": null, "numpy_type": "object", "pandas_type": "unicode"}], "columns": [{"field_name": "B", "metadata": null, "name": "B", "numpy_type": "boolean", "pandas_type": "bool"}, {"field_name": "I", "metadata": null, "name": "I", "numpy_type": "int64", "pandas_type": "int64"}, {"field_name": "b", "metadata": null, "name": "b", "numpy_type": "bool", "pandas_type": "bool"}, {"field_name": "i", "metadata": null, "name": "i", "numpy_type": "int64", "pandas_type": "int64"}, {"field_name": "o", "metadata": null, "name": "o", "numpy_type": "object", "pandas_type": "unicode"}, {"field_name": "s", "metadata": null, "name": "s", "numpy_type": "string", "pandas_type": "unicode"}], "creator": {"library": "pyarrow", "version": "1.0.1"}, "index_columns": [{"kind": "range", "name": null, "start": 0, "step": 1, "stop": 2}], "pandas_version": "1.1.3"}\x00\x18\x0cARROW:schema\x18\xe0\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\x00\x18"parquet-cpp version 1.5.1-SNAPSHOT\x19l\x1c\x00\x00\x1c\x00\x00\x1c\x00\x00\x1c\x00\x00\x1c\x00\x00\x1c\x00\x00\x00#\x0b\x00\x00PAR1'

[fjetter]

IIUC, this affects only the schema but we're able to read the data properly?

[fjetter]

Looks like this is because arrow doesn't distinguish between the two and we're defining the _common_metadata purely via the arrow types

In [1]: import pyarrow as pa

In [2]: import pandas as pd

In [3]: df = pd.DataFrame({"Int": pd.Series([1, pd.NA], dtype="Int64")})

In [4]: schema = pa.Schema.from_pandas(df)

In [5]: schema
Out[5]:
Int: int64

I'd be curious if there are any practical implications for this discrepancy or if this is rather a 'formal' error

[mlondschien]

We use Kartothek datasets to cache computation results. For validation, we check if the Kartothek metadata matches the expected dtypes. We've not had any issues loading data with such columns yet. So this is mostly an inconvenience (or "formal" error).

[fjetter]

That's very interesting and I'm positively surprised that this works generally. afaik, we do not have any tests using the nullables types in kartothek, yet (but it's about time). If you want to contribute on that front, I suggest to start with adding some nullable ints/bools to

kartothek/kartothek/serialization/testing.py

Line 27 in 6514c1f

def get_dataframe_not_nested(n):

and see what breaks

If I understand this correctly, it also only affects integers, correct? bool(eans) are correctly reconstructed.

I assume this is connected to us stripping the metadata from the schema. I'm just wondering why it works for bools

kartothek/kartothek/core/common_metadata.py

Lines 612 to 614 in 6514c1f

	reference_to_compare = _strip_columns_from_schema(
	reference, null_columns
	).remove_metadata()

 dm.table_meta["table"].internal().empty_table().to_pandas().dtypes
Out[5]:
B    boolean
I      int64
b       bool
i      int64
o     object
s     string
dtype: object

[mlondschien]

We're not using these in production but have tests (that need skipping). Is there a specific reason you are not testing for categoricals?

[fjetter]

Is there a specific reason you are not testing for categoricals

We do have tests for categoricals but not systematically as part of the "all types dataframes"