System.Data.SQLite
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Ticket UUID: 8f05349da78773f4dfc29ace794ad174b909917b
Title: Support for windowing functions in Sqlite EF6
Status: Open Type: Feature_Request
Severity: Important Priority: Medium
Subsystem: LINQ Resolution: Under_Review
Last Modified: 2019-04-03 08:59:16
Version Found In: Sqlite 3.25 and newer
User Comments:
anonymous added on 2019-04-02 11:52:03:

Sqlite 3.25 introduced windowing functions, however they are not usable via EF6 with Sqlite.

using EF6 with Sqlite you cannot use Skip() at all and cannot use GroupBy() in a way that would require windowing functions, as they result in a NotSupportedException.

For example,

Table.OrderBy(t => t.colname).Skip(50)
could be translated to
select *
from (select t.*,
             row_number() over (order by t.colname) as rownum
      from table t)
where rownum > 50


Complex groupings can be solved with window functions as well, for example
Table.GroupBy(t => t.col1).Select(g => g.OrderBy(t => t.col2).First())
can be translated to
select t.*
from table t
join ( select *,
              row_number() over (partition by col1 order by col2) rownum
       from table ) x on t.id = x.id
where x.rownum = 1


when using EF6 with sql server these types of linq funtions would produce queries that use windowing functions (mostly row_number). It would be great if Sqlite could do this too, at least for the row_number window. Perhaps you could model it off the sql server EF6 provider, if that is at all possible, since it seems to be able to handle extremely complex linq queries very well.


anonymous added on 2019-04-03 08:59:16:

on further thought, the second example would translate more like this if you were to use sql server EF6:

select [all columns except rownum]
from ( select *,
              row_number() over (partition by col1 order by col2) rownum
       from table ) x
where x.rownum = 1