bkmgit commented on a change in pull request #11882:
URL: https://github.com/apache/arrow/pull/11882#discussion_r786216564
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File path: cpp/src/arrow/compute/kernels/scalar_compare.cc
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@@ -156,39 +212,52 @@ struct Maximum {
}
};
+// Check if timestamp timezones are comparable (either all are empty or none
is).
+Status CheckCompareTimestamps(const ExecBatch& batch) {
+ if (batch.num_values() > 0) {
+ for (int i = 0; i < batch.num_values() - 1; ++i) {
+ const auto& tsi = checked_cast<const TimestampType&>(*batch[i].type());
+ for (int j = i + 1; j < batch.num_values(); ++j) {
Review comment:
The comparison is done using [Boolean
algebra](https://en.wikipedia.org/wiki/Boolean_algebra#Basic_operations) which
has the truth table:
| x | y | x^y |
|--- |--- |--- |
| 1 | 1 | 1 |
| 1 | 0 | 0 |
| 0 | 1 | 0 |
| 0 | 0 | 1 |
Thus ( 1^1) ^ 1 = 0, ( 1 ^ 0 ) ^ 1 = 0 and ( 1 ^ 1 ) ^ 0 = 1 which are not
the result we want. To keep the code general and extensible, a double loop
that allows for pairwise comparisons will give the correct results.
Another option could be to cast to integers, sum the results and check if
the sum is either 0 or batch.numvalues()
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