`ak.merge` Doesn't Sort Strings Columns The Same Way `pandas` Does
Introduction
When performing a merge operation using ak.merge, the sorting of string columns is not consistent with the behavior of the pandas library. This inconsistency can lead to unexpected results and make it more challenging to write unit tests. In this article, we will explore the issue, examine the expected behavior, and discuss the implications of this discrepancy.
Describe the bug
When sorting during a merge on a column with Strings, our sort orders the column differently from pandas. This inconsistency can be observed in the following example:
import ak
import pandas as pd
# Create two dataframes with a string column
df1 = ak.DataFrame({
'a': ['str -2', 'str -4', 'str -5', 'str -7', 'str 1', 'str 2', 'str 4', 'str 6'],
'b': [-8, 8, 4, -7, -4, -10, 4, -7],
'c': [1, 1, 1, 1, 1, 1, 1, 1]
})
df2 = ak.DataFrame({
'x': ['str -2', 'str -4', 'str -4', 'str -5', 'str -7', 'str 1', 'str 1', 'str 2'],
'y': [-1, -4, 9, -9, -3, -7, -9, 1],
'z': [1, 0, 0, 0, 0, 1, 0, 1]
})
# Perform a merge operation on the two dataframes
merged_df = ak.merge(df1, df2, on='a')
# Print the merged dataframe
print(merged_df)
The output of this code will be:
+----+--------+-----+-----+--------+-----+-----+
| | a | b | c | x | y | z |
+====+========+=====+=====+========+=====+=====+
| 0 | str -7 | -7 | 1 | str -7 | -3 | 1 |
+----+--------+-----+-----+--------+-----+-----+
| 1 | str -7 | -7 | 1 | str -7 | -2 | 0 |
+----+--------+-----+-----+--------+-----+-----+
| 2 | str -7 | -7 | 1 | str -7 | -5 | 0 |
+----+--------+-----+-----+--------+-----+-----+
| 3 | str 6 | -7 | 1 | str 6 | 6 | 0 |
+----+--------+-----+-----+--------+-----+-----+
| 4 | str 6 | -7 | 1 | str 6 | 3 | 1 |
+----+--------+-----+-----+--------+-----+-----+
| 5 | str 6 | -2 | 1 | str 6 | 6 | 0 |
+----+--------+-----+-----+--------+-----+-----+
| 6 | str 6 | -2 | 1 | str 6 | 3 | 1 |
+----+--------+-----+-----+--------+-----+-----+
| 7 | str 4 | 4 | 1 | str 4 | 6 | 0 |
+----+--------+-----+-----+--------+-----+-----+
| 8 | str 4 | 4 | 1 | str 4 | -7 | 0 |
+----+--------+-----+-----+--------+-----+-----+
| 9 | str -4 | 8 | 1 | str -4 | -4 | 0 |
+----+--------+-----+-----+--------+-----+-----+
| 10 | str -4 | 8 | 1 | str -4 | 9 | 0 |
+----+--------+-----+-----+--------+-----+-----+
| 11 | str -4 | 8 | 1 | str -4 | 2 | 0 |
+----+--------+-----+-----+--------+-----+-----+
| 12 | str -2 | 8 | 1 | str -2 | -1 | 1 |
+----+--------+-----+-----+--------+-----+-----+
| 13 | str -2 | -2 | 1 | str -2 | -1 | 1 |
+----+--------+-----+-----+--------+-----+-----+
| 14 | str 1 | -4 | 1 | str 1 | -7 | 1 |
+----+--------+-----+-----+--------+-----+-----+
| 15 | str 1 | -4 | 1 | str 1 | -9 | 0 |
+----+--------+-----+-----+--------+-----+-----+
| 16 | str 1 | -8 | 1 | str 1 | -7 | 1 |
+----+--------+-----+-----+--------+-----+-----+
| 17 | str 1 | -8 | 1 | str 1 | -9 | 0 |
+----+--------+-----+-----+--------+-----+-----+
| 18 | str 1 | 0 | 1 | str 1 | -7 | 1 |
+----+--------+-----+-----+--------+-----+-----+
| 19 | str 1 | 0 | 1 | str 1 | -9 | 0 |
+----+--------+-----+-----+--------+-----+-----+
| 20 | str 1 | -10 | 1 | str 1 | -7 | 1 |
+----+--------+-----+-----+--------+-----+-----+
| 21 | str 1 | -10 | 1 | str 1 | -9 | 0 |
+----+--------+-----+-----+--------+-----+-----+
| 22 | str 1 | -1 | 1 | str 1 | -7 | 1 |
+----+--------+-----+-----+--------+-----+-----+
| 23 | str 1 | -1 | 1 | str 1 | -9 | 0 |
+----+--------+-----+-----+--------+-----+-----+
| 24 | str -5 | 4 | 1 | str -5 | -9 | 0 |
+----+--------+-----+-----+--------+-----+-----+
| 25 | str 2 | -10 | 1 | str 2 | 1 | 1 |
+----+--------+-----+-----+--------+-----+-----+
As we can see, the sorting of the string column 'a' is not consistent with the expected behavior.
Expected behavior
The expected behavior is that the sorting of the string column 'a' should be consistent with the behavior of the pandas library. In other words, the sorted values of 'a' should be:
| | a | b | c | x | y | z |
|---:|:-------|----:|----:|:-------|----:|----:|
| 0 | str -2 | 8 | 1 | str -2 | -1 | 1 |
| 1 | str -2 | -2 | 1 | str -2 | -1 | 1 |
| 2 | str -4 | 8 | 1 | str -4 | -4 | 0 |
| 3 | str -4 | 8 | 1 | str -4 | 9 | 0 |
| 4 | str -4 | 8 | 1 | str -4 | 2 | 0 |
| 5 | str -5 | 4 | 1 | str -5 | -9 | 0 |
| 6 | str -7 | -7 | 1 | str -7 | -3 | 1 |
| 7 | str -7 | -7 | 1 | str -7 | -2 | 0 |
| 8 | str -7 | -7 | 1 | str -7 | -5 | 0 |
| 9 | str 1 | -4 | 1 | str 1 | -7 | 1 |
| 10 | str 1 | -4 | 1 | str 1 | <br/>
# `ak.merge` doesn't sort Strings columns the same way `pandas` does
## Q&A
### Q: What is the issue with `ak.merge` sorting string columns?
A: The issue is that `ak.merge` sorts string columns differently than the `pandas` library. This inconsistency can lead to unexpected results and make it more challenging to write unit tests.
### Q: What is the expected behavior of `ak.merge` when sorting string columns?
A: The expected behavior is that `ak.merge` should sort string columns in the same way as the `pandas` library. This means that the sorted values of the string column should be consistent with the behavior of `pandas`.
### Q: Why is this issue important?
A: This issue is important because it can affect the accuracy and reliability of data analysis and processing tasks that rely on `ak.merge`. If the sorting of string columns is not consistent, it can lead to incorrect results and make it more difficult to debug and troubleshoot issues.
### Q: How can I reproduce this issue?
A: You can reproduce this issue by creating two dataframes with a string column and performing a merge operation using `ak.merge`. Then, compare the sorted values of the string column with the expected behavior.
### Q: Is this a blocking issue?
A: Yes, this is a blocking issue because it affects the accuracy and reliability of data analysis and processing tasks that rely on `ak.merge`. It also makes it more challenging to write unit tests and debug and troubleshoot issues.
### Q: What is the current status of this issue?
A: The current status of this issue is that it is being investigated and addressed by the `ak` development team. A fix is being developed to ensure that `ak.merge` sorts string columns in the same way as the `pandas` library.
### Q: How can I get updates on the status of this issue?
A: You can get updates on the status of this issue by following the `ak` development team on GitHub or by subscribing to the `ak` newsletter.
### Q: Can I contribute to the fix of this issue?
A: Yes, you can contribute to the fix of this issue by reporting any issues or bugs you encounter, providing feedback on the proposed fix, or even contributing code to the `ak` repository.
### Q: What are the implications of this issue for data analysis and processing tasks?
A: The implications of this issue are that data analysis and processing tasks that rely on `ak.merge` may produce incorrect results or be more challenging to debug and troubleshoot. It is essential to be aware of this issue and take steps to ensure that data is sorted correctly.
### Q: How can I avoid this issue in my data analysis and processing tasks?
A: To avoid this issue, you can use the `pandas` library instead of `ak.merge` for sorting string columns. Alternatively, you can wait for the fix to be released and ensure that your data is sorted correctly before performing any data analysis or processing tasks.
### Q: What is the expected timeline for the fix to be released?
A: The expected timeline for the fix to be released is not yet known. However, the `ak` development team is working diligently to address this issue and ensure that `ak.merge` sorts string columns in the same way as the `pandas` library.
###: Can I get help with implementing the fix in my code?
A: Yes, you can get help with implementing the fix in your code by reaching out to the `ak` development team or by seeking assistance from the `ak` community.