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From Wenchen Fan <cloud0...@gmail.com>
Subject Re: Spark Data Frame. PreSorded partitions
Date Mon, 04 Dec 2017 14:43:20 GMT
Data Source V2 is still under development. Ordering reporting is one of the
planned features, but it's not done yet, we are still thinking about what
the API should be, e.g. we need to include sort order, null first/last and
other sorting related properties.

On Mon, Dec 4, 2017 at 10:12 PM, Николай Ижиков <nizhikov.dev@gmail.com>
wrote:

> Hello, guys.
>
> Thank you for answers!
>
> > I think pushing down a sort .... could make a big difference.
> > You can however proposes to the data source api 2 to be included.
>
> Jörn, are you talking about this jira issue? -
> https://issues.apache.org/jira/browse/SPARK-15689
> Is there any additional documentation I has to learn before making any
> proposition?
>
>
>
> 04.12.2017 14:05, Holden Karau пишет:
>
>> I think pushing down a sort (or really more in the case where the data is
>> already naturally returned in sorted order on some column) could make a big
>> difference. Probably the simplest argument for a lot of time being spent
>> sorting (in some use cases) is the fact it's still one of the standard
>> benchmarks.
>>
>> On Mon, Dec 4, 2017 at 1:55 AM, Jörn Franke <jornfranke@gmail.com
>> <mailto:jornfranke@gmail.com>> wrote:
>>
>>     I do not think that the data source api exposes such a thing. You can
>> however proposes to the data source api 2 to be included.
>>
>>     However there are some caveats , because sorted can mean two
>> different things (weak vs strict order).
>>
>>     Then, is really a lot of time lost because of sorting? The best thing
>> is to not read data that is not needed at all (see min/max indexes in
>> orc/parquet or bloom filters in Orc). What is not read
>>     does not need to be sorted. See also predicate pushdown.
>>
>>      > On 4. Dec 2017, at 07:50, Николай Ижиков <nizhikov.dev@gmail.com
>> <mailto:nizhikov.dev@gmail.com>> wrote:
>>      >
>>      > Cross-posting from @user.
>>      >
>>      > Hello, guys!
>>      >
>>      > I work on implementation of custom DataSource for Spark Data Frame
>> API and have a question:
>>      >
>>      > If I have a `SELECT * FROM table1 ORDER BY some_column` query I
>> can sort data inside a partition in my data source.
>>      >
>>      > Do I have a built-in option to tell spark that data from each
>> partition already sorted?
>>      >
>>      > It seems that Spark can benefit from usage of already sorted
>> partitions.
>>      > By using of distributed merge sort algorithm, for example.
>>      >
>>      > Does it make sense for you?
>>      >
>>      >
>>      > 28.11.2017 18:42, Michael Artz пишет:
>>      >> I'm not sure other than retrieving from a hive table that is
>> already sorted.  This sounds cool though, would be interested to know this
>> as well
>>      >> On Nov 28, 2017 10:40 AM, "Николай Ижиков" <
>> nizhikov.dev@gmail.com <mailto:nizhikov.dev@gmail.com> <mailto:
>> nizhikov.dev@gmail.com <mailto:nizhikov.dev@gmail.com>>> wrote:
>>      >>    Hello, guys!
>>      >>    I work on implementation of custom DataSource for Spark Data
>> Frame API and have a question:
>>      >>    If I have a `SELECT * FROM table1 ORDER BY some_column` query
>> I can sort data inside a partition in my data source.
>>      >>    Do I have a built-in option to tell spark that data from each
>> partition already sorted?
>>      >>    It seems that Spark can benefit from usage of already sorted
>> partitions.
>>      >>    By using of distributed merge sort algorithm, for example.
>>      >>    Does it make sense for you?
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>>
>>
>> --
>> Twitter: https://twitter.com/holdenkarau
>>
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