BUG: Fix #57608: queries on categorical string columns in HDFStore.select() return unexpected results. #61225
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HDFStore.select() return unexpected results. In function __init__() of class Selection (pandas/core/io/pytables.py), the method self.terms.evaluate() was not returning the correct value for the where condition. The issue stemmed from the function convert_value() of class BinOp (pandas/core/computation/pytables.py), where the function searchedsorted() did not return the correct index when matching the where condition in the metadata (categories table). Replacing searchsorted() with np.where() resolves this issue.
mroeschke
reviewed
Apr 3, 2025
pandas/core/computation/pytables.py
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| @@ -239,7 +239,8 @@ def stringify(value): | |||
| if conv_val not in metadata: | |||
| result = -1 | |||
| else: | |||
| result = metadata.searchsorted(conv_val, side="left") | |||
| # Find the index of the first match of conv_val in metadata | |||
| result = np.where(metadata == conv_val)[0][0] | |||
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Suggested change
| result = np.where(metadata == conv_val)[0][0] | |
| result = np.flatnonzero(metadata == conv_val)[0] |
Also is it possible to know if metadata is sorted ahead of time so we can use searchsorted? it will be much faster in that case
mroeschke
reviewed
Apr 4, 2025
| @@ -239,7 +239,13 @@ def stringify(value): | |||
| if conv_val not in metadata: | |||
| result = -1 | |||
| else: | |||
| result = metadata.searchsorted(conv_val, side="left") | |||
| # Check if metadata is sorted | |||
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Well we probably won't want to do this check here because this also incurs some performance penalty. I was just staying if there's something in the preprocessing code above that already checked this for us.
If not, just using np.flatnonzero here directly is fine
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It doesn’t look like there’s a check to ensure the metadata is ordered — this part seems to work with just the array of the category values, so it may not be able to confirm whether it was ordered
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In function init() of class Selection (pandas/core/io/pytables.py), the method self.terms.evaluate() was not returning the correct value for the where condition. The issue stemmed from the function convert_value() of class BinOp (pandas/core/computation/pytables.py), where the function searchedsorted() did not return the correct index when matching the where condition in the metadata (categories table). Replacing searchsorted() with np.where() resolves this issue.
doc/source/whatsnew/vX.X.X.rstfile if fixing a bug or adding a new feature.