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Known Python Issues

Unfortunately there are some issues that are either beyond our control or are very elusive / hard to track down. Below is a list of these issues that you might have to be aware of, depending on your workflow.

Numpy Import Multithreading

When making use of multi threading and fetching results either directly as Numpy arrays or indirectly through a Pandas DataFrame, it might be necessary to ensure that numpy.core.multiarray is imported. If this module has not been imported from the main thread, and a different thread during execution attempts to import it this causes either a deadlock or a crash.

To avoid this, it's recommended to import numpy.core.multiarray before starting up threads.

DESCRIBE and SUMMARIZE Return Empty Tables in Jupyter

The DESCRIBE and SUMMARIZE statements return an empty table:

%sql
CREATE OR REPLACE TABLE tbl AS (SELECT 42 AS x);
DESCRIBE tbl;

To work around this, wrap them into a subquery:

%sql
CREATE OR REPLACE TABLE tbl AS (SELECT 42 AS x);
FROM (DESCRIBE tbl);

Protobuf Error for JupySQL in IPython

Loading the JupySQL extension in IPython fails:

In [1]: %load_ext sql

ImportError: cannot import name 'builder' from 'google.protobuf.internal' (unknown location)

The solution is to fix the protobuf package. This may require uninstalling conflicting packages, e.g.:

%pip uninstall tensorflow
%pip install protobuf

Running EXPLAIN Renders Newlines

In Python, the output of the EXPLAIN statement contains hard line breaks (\n):

In [1]: import duckdb
   ...: duckdb.sql("EXPLAIN SELECT 42 AS x")

Out[1]:
┌───────────────┬───────────────────────────────────────────────────────────────────────────────────────────────────────────────────┐
│  explain_key  │                                                   explain_value                                                   │
│    varchar    │                                                      varchar                                                      │
├───────────────┼───────────────────────────────────────────────────────────────────────────────────────────────────────────────────┤
│ physical_plan │ ┌───────────────────────────┐\n│         PROJECTION        │\n│   ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─   │\n│             x   …  │
└───────────────┴───────────────────────────────────────────────────────────────────────────────────────────────────────────────────┘

To work around this, print the output of the explain() function:

In [2]: print(duckdb.sql("SELECT 42 AS x").explain())

Out[2]:
┌───────────────────────────┐
│         PROJECTION        │
│   ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─   │
│             x             │
└─────────────┬─────────────┘
┌─────────────┴─────────────┐
│         DUMMY_SCAN        │
└───────────────────────────┘

Please also check out the Jupyter guide for tips on using Jupyter with JupySQL.

Error When Importing the DuckDB Python Package on Windows

When importing DuckDB on Windows, the Python runtime may return the following error:

import duckdb

ImportError: DLL load failed while importing duckdb: The specified module could not be found.

The solution is to install the Microsoft Visual C++ Redistributable package.

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