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Posted to github@arrow.apache.org by GitBox <gi...@apache.org> on 2021/08/18 13:52:40 UTC
[GitHub] [arrow-rs] alamb opened a new issue #696: Add documentation examples for `regexp_match` kernels
alamb opened a new issue #696:
URL: https://github.com/apache/arrow-rs/issues/696
**Is your feature request related to a problem or challenge? Please describe what you are trying to do.**
The current documentation for the `regexp_match` kernel is quite sparse:
https://docs.rs/arrow/5.2.0/arrow/compute/kernels/regexp/fn.regexp_match.html
Also, since this function returns `ArrayRef` (aka untyped generic Array), I was personally a bit confused that `regexp_match` actually returns a `ListArray` with the matches. Having this documented would help a lot.
**Describe the solution you'd like**
1. A description of the type of the array that is returned
2. A doc example (can probably adapt a test in the code) that shows how to invoke `regexp_match` and use the returned `ListArray`
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[GitHub] [arrow-rs] matthewmturner commented on issue #696: Add documentation examples for `regexp_match` kernels
Posted by GitBox <gi...@apache.org>.
matthewmturner commented on issue #696:
URL: https://github.com/apache/arrow-rs/issues/696#issuecomment-912904126
I can give this a shot
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[GitHub] [arrow-rs] matthewmturner commented on issue #696: Add documentation examples for `regexp_match` kernels
Posted by GitBox <gi...@apache.org>.
matthewmturner commented on issue #696:
URL: https://github.com/apache/arrow-rs/issues/696#issuecomment-916964428
@alamb unfortunately not, same result.
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[GitHub] [arrow-rs] seddonm1 commented on issue #696: Add documentation examples for `regexp_match` kernels
Posted by GitBox <gi...@apache.org>.
seddonm1 commented on issue #696:
URL: https://github.com/apache/arrow-rs/issues/696#issuecomment-917497090
Thanks @matthewmturner i will have a look
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[GitHub] [arrow-rs] matthewmturner edited a comment on issue #696: Add documentation examples for `regexp_match` kernels
Posted by GitBox <gi...@apache.org>.
matthewmturner edited a comment on issue #696:
URL: https://github.com/apache/arrow-rs/issues/696#issuecomment-913013809
@alamb im playing around with the `regexp_match` function and struggling to produce the expected results. I tried to do something similar to the test `match_single_group`.
I have the following:
```
let array = StringArray::from(vec![Some("Animal"), None, Some("House")]);
let pat = StringArray::from(vec![r"^[A]"; 3]);
let m = regexp_match(&array, &pat, None).unwrap();
let result = m.as_any().downcast_ref::<ListArray>().unwrap();
let elem_builder: GenericStringBuilder<i32> = GenericStringBuilder::new(0);
let mut expected_builder = ListBuilder::new(elem_builder);
expected_builder.values().append_value("A").unwrap();
expected_builder.append(true).unwrap();
expected_builder.append(false).unwrap();
expected_builder.append(false).unwrap();
let expected = expected_builder.finish();
assert_eq!(&expected, result);
```
But get the following:
```
thread 'main' panicked at 'assertion failed: `(left == right)`
left: `ListArray
[
StringArray
[
"A",
],
null,
null,
]`,
right: `ListArray
[
StringArray
[
],
null,
null,
]`', src/main.rs:54:5
```
It's not clear to me why the result StringArray at the first index of the ListArray doesnt have "A" - its just an empty StringArray.
Any thoughts?
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[GitHub] [arrow-rs] alamb commented on issue #696: Add documentation examples for `regexp_match` kernels
Posted by GitBox <gi...@apache.org>.
alamb commented on issue #696:
URL: https://github.com/apache/arrow-rs/issues/696#issuecomment-916991654
🤔 I don't have a good answer then. It would require some more debugging
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[GitHub] [arrow-rs] alamb commented on issue #696: Add documentation examples for `regexp_match` kernels
Posted by GitBox <gi...@apache.org>.
alamb commented on issue #696:
URL: https://github.com/apache/arrow-rs/issues/696#issuecomment-916953170
@matthewmturner I also don't understand that -- if you remove the caret and use `[A]` as the regex does it do the right thing? Perhaps @seddonm1 has some hints as well
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[GitHub] [arrow-rs] matthewmturner commented on issue #696: Add documentation examples for `regexp_match` kernels
Posted by GitBox <gi...@apache.org>.
matthewmturner commented on issue #696:
URL: https://github.com/apache/arrow-rs/issues/696#issuecomment-917427288
@seddonm1 i believe postgres works as expected. i did the below.
```
postgres=# WITH vals(a) AS (VALUES ('Animal'), (null), ('House'))
SELECT a, regexp_matches(a, '^[A]') m from vals;
```
Resulting in
```
a | m
--------+-----
Animal | {A}
(1 row)
```
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[GitHub] [arrow-rs] matthewmturner commented on issue #696: Add documentation examples for `regexp_match` kernels
Posted by GitBox <gi...@apache.org>.
matthewmturner commented on issue #696:
URL: https://github.com/apache/arrow-rs/issues/696#issuecomment-913013809
@alamb im playing around with the regexp_match function and struggling to produce the expected results. I tried to do something similar to the test `match_single_group`.
I have the following:
```
let array = StringArray::from(vec![Some("Animal"), None, Some("House")]);
let pat = StringArray::from(vec![r"^[A]"; 3]);
let m = regexp_match(&array, &pat, None).unwrap();
let result = m.as_any().downcast_ref::<ListArray>().unwrap();
let elem_builder: GenericStringBuilder<i32> = GenericStringBuilder::new(0);
let mut expected_builder = ListBuilder::new(elem_builder);
expected_builder.values().append_value("A").unwrap();
expected_builder.append(true).unwrap();
expected_builder.append(false).unwrap();
expected_builder.append(false).unwrap();
let expected = expected_builder.finish();
assert_eq!(&expected, result);
```
But get the following:
```
thread 'main' panicked at 'assertion failed: `(left == right)`
left: `ListArray
[
StringArray
[
"A",
],
null,
null,
]`,
right: `ListArray
[
StringArray
[
],
null,
null,
]`', src/main.rs:54:5
```
It's not clear to me why the result StringArray at the first index of the ListArray doesnt have "A" - its just an empty StringArray.
Any thoughts?
--
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[GitHub] [arrow-rs] seddonm1 commented on issue #696: Add documentation examples for `regexp_match` kernels
Posted by GitBox <gi...@apache.org>.
seddonm1 commented on issue #696:
URL: https://github.com/apache/arrow-rs/issues/696#issuecomment-917309048
@alamb Sorry I didn't do this one. It does appear there may be a defect.
@matthewmturner are you able to reproduce the behaviour to verify that it behaves differently to Postgres? (https://www.postgresql.org/docs/current/functions-matching.html)
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[GitHub] [arrow-rs] matthewmturner commented on issue #696: Add documentation examples for `regexp_match` kernels
Posted by GitBox <gi...@apache.org>.
matthewmturner commented on issue #696:
URL: https://github.com/apache/arrow-rs/issues/696#issuecomment-917324963
@seddonm1 sure, will give it a shot.
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