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https://issues.apache.org/jira/browse/ARROW-16616?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17557141#comment-17557141
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Will Jones edited comment on ARROW-16616 at 6/21/22 9:56 PM:
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I'm a little cautious about the idea of {{Dataset.filter()}} returning a
{{Dataset}}, since it mixes up the purpose of {{Dataset}} and {{Scanner}}. If
it did, what would this return then?
{code:python}
ds.filter(ds.field("x") > 2).scan(filter=ds.field("y") < 3)
{code}
I think it might be better if {{Dataset.filter()}} returned a scanner with that
filter. And then {{Scanner}} could also have {{filter()}} and {{project()}}
methods to allow chaining. So you could do:
{code:python}
(
ds.filter(ds.field("x") > 2)
.filter(ds.field("y") < 4)
.project("x", "y", "z")
.to_table()
)
{code}
What do you think of that?
was (Author: willjones127):
I'm a little cautious about the idea of {{Dataset.filter()}} returning a
{{Dataset}}, since it mixes up the purpose of {{Dataset}} and {{Scanner}}. If
it did, what would this return then?
{code:python}
ds.filter(ds.field("x") > 2).scan(filter=ds.field("y") < 3)
{code}
I think it might be better if {{Dataset.filter()}} returned a scanner with that
filter. And then {{Scanner}} could also have {{filter()}} and {{project()}}
methods to allow chaining. What do you think of that?
> [Python] Allow lazy evaluation of filters in Dataset and add Datset.filter
> method
> ---------------------------------------------------------------------------------
>
> Key: ARROW-16616
> URL: https://issues.apache.org/jira/browse/ARROW-16616
> Project: Apache Arrow
> Issue Type: Sub-task
> Components: Python
> Reporter: Alessandro Molina
> Priority: Major
> Labels: pull-request-available
> Fix For: 9.0.0
>
> Time Spent: 0.5h
> Remaining Estimate: 0h
>
> To keep the {{Dataset}} api compatible with the {{Table}} one in terms of
> analytics capabilities, we should add a {{Dataset.filter}} method. The
> initial POC was based on {{_table_filter}} but that required materialising
> all the {{Dataset}} content after filtering as it returned an
> {{{}InMemoryDataset{}}}.
> Given that {{Scanner}} can filter a dataset without actually materialising
> the data until a final step happens, it would be good to have
> {{Dataset.filter}} return some form of lazy dataset when the filter is only
> stored aside and the Scanner is created when data is actually retrieved.
> PS: Also update {{test_dataset_filter}} test to use the {{Dataset.filter}}
> method
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