Discussion about replacing CTE with other query using linq2db

This it not really an issue, it’s a continuation of a discussion here

Steps to reproduce

Here is the goal of the query I’m trying to generate and why I was initially using CTE.

When test results are updated for a given equipment, I need to reprocess them with previous results on the same equipment to compute rates of changes between results (also need to check if there are more recent results for the same equipment as their respective rates of change will also be affected by changing the “current” results).

Here is the query I’m using (put in context with the table below)

var queryResult = await _dbContext.TestResults.FromSqlRaw($@"
    WITH equipmentResults AS
    (
        SELECT ROW_NUMBER() OVER (Order BY EquipmentId, TestDate) AS rn
        , *
        FROM dbo.TestResults
        WHERE EquipmentId IN (1,2)                            
    ),
    relatedRowNumbers AS 
    (
        SELECT
        rn AS currentResultRN,
        rn+1 AS nextResultRN
        from equipmentResults
        WHERE Id IN (4,10)
    )
    SELECT * from equipmentResults
    WHERE rn IN (select currentResultRN from relatedRowNumbers) OR rn IN (select nextResultRN from relatedRowNumbers)")
.ToListAsync();

To accomplish this I do the following:

First create a list of all the equipment for which results have been updated since last rate compute task has run. This list is used as a parameter to the 1st CTE, which returns me a list containing all the test results of all the specified equipment (in the example equipment with id 1 and 2).

Once I have this list, I then need to find the specific rows for which results have been updated, and then go on to find their adjacent rows (results are also sorted by date in 1st CTE). This is what the 2nd CTE is used for (attributing row numbers (here the window function could be beneficial I guess)

Here is an example result table after running 1st CTE, in which I identified the rows that I need to retrieve in the final result (and for which I used the 2nd CTE and final SELECT clause). So at the end, EF would need to return rows with rn in (3,4,5,9,10,11) or ResultsRowId in (3,4,5,54,108,109) if not using second CTE

Rn	EquipmentId	ResultsRowId	Date Updated	Note
1	1	1	2020-06-05
2	1	2	2020-06-06
3	1	3	2020-06-07	Previous relative to 1st
4	1	4	2020-06-08	1st results row updated
5	1	5	2020-06-09	Next (relative to 1st)
6	2	28	2020-06-10
7	2	29	2020-06-11
8	2	31	2020-06-12
9	2	54	2020-06-13	Previous
10	2	108	2020-06-14	2nd results row updated
11	2	109	2020-06-15	Next
12	2	111	2020-06-16
13	2	112	2020-06-17

Environment details

linq2db version: None yet 😃 Database Server: SQL Server Database Provider: MS SQL Server Operating system: Windows 10 .NET Framework: .net core 3.1

[sdanyliv]

Yes, good place. I’ll find time to support properties convertors, but it is not simple task.

[sdanyliv]

Oh, yes, we have limitations. Currently we do not support entity property value conversion. But it’s easy to solve. ONCE per application.

MappingSchema.Default.SetConverter<string, SingleTestResultsTemplate>(str => 
   // do Newtonsoft deserialization here
)