Pagination over large tables slow

There is a significant performance drop in Oracle’s adapter for EF Core compared to EF6 when selecting from a table with 2 million rows. EF6 is using a different approach for computing the row number required for paging.

EF6

SELECT * 
FROM ( 
SELECT 
"Extent1"."Id" AS "Id"
FROM ( SELECT "Extent1"."Id" AS "Id", row_number() OVER (ORDER BY "Extent1"."Id" DESC) AS "row_number"
	FROM "Table" "Extent1"
)  "Extent1"
WHERE ("Extent1"."row_number" > :p__linq__0)
ORDER BY "Extent1"."ID" DESC
)
WHERE (ROWNUM <= (:p__linq__1))

EF Core

Select
 K0 "Id"
 from (
  select 
    "m2".*, 
    rownum r2 
  from
    (
    SELECT "t"."Id" K0
    FROM "Table" "t"

    ORDER BY "t"."Id" DESC
    ) "m2"
) "m1"
where r2 > :p_0
and r2 <= (:p_0 + :p_1)

I am using Oracle 11g (11.2.0.3.0) and have set compatibility level to 11 when configuring the DbContext.

[alexkeh]

Got the repro. We’ll take a look.

[alexkeh]

@iulianb I just toggled the bug status to be viewable to customers. Within 24 hours, you should be able to view the bug from MOS. I don’t know why Oracle Support couldn’t find it. They should be able to view internal bugs.