Issue Details (XML | Word | Printable)

Key: DNET-876
Type: Bug Bug
Status: Closed Closed
Resolution: Won't Fix
Priority: Major Major
Assignee: Jiri Cincura
Reporter: Vladimir Karataev
Votes: 0
Watchers: 0

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.NET Data provider

Using wrong type for blob

Created: 11/Apr/19 12:03 PM   Updated: 15/Apr/19 06:22 AM
Component/s: ADO.NET Provider
Affects Version/s:
Fix Version/s: None

File Attachments: 1. File ConsoleApp1.7z (202 kB)

Environment: core, microsoft.entityframeworkCore 2.2.4
Firebird 2.5

 Description  « Hide
I am using next data model:

public class Test
public long Id {get; set; }

public byte[] raw_data {get; set; }

The column "raw_data" was descripted as: BLOB SUB_TYPE 1 SEGMENT SIZE 100 CHARACTER SET UTF8;

This is a BLOB.

I execute request of data from table through entity framework:

var data = db.Test.Find(id);

In window trace into visual studio i watch query:

SELECT "e"."ID", "e"."RAW_DATA" FROM "TABLE" AS "e" WHERE "e"."ID" = CAST(@__get_Item_0 AS BIGINT)

I have got exception in this place:

"Unable to cast object of type 'System.String' to type 'System.Byte[]'."

I suppose, provider should be using blob type for this column, but it using type of string for this column. May be it wrong behavior?

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Jiri Cincura added a comment - 11/Apr/19 12:20 PM
The table on latest providers gets this definition:
CREATE TABLE "table" (
    "raw_data" BLOB SUB_TYPE BINARY,

Which is correct.

Even the query is different:
      SELECT "e"."Id", "e"."raw_data"
      FROM "table" AS "e"
      WHERE "e"."Id" = CAST(@__get_Item_0 AS BIGINT)
      ROWS (1)

Can you provide reproducible test code?

Vladimir Karataev added a comment - 11/Apr/19 03:16 PM
Provider work fine with SUB_TYPE BINARY, and map on byte[] type in c# code.
Problem only with SUB_TYPE 1.

I found workaround: db.Test.FromSql("...cast(raw_Data as blob sub_type 0)...")

An sad moments in such case. Entity generate query like "select from select".

And interesting moment. On UPDATE query byte[] mapping on BLOB SUB_TYPE 1 perfect.

Only SELECT query make wrong mapping BLOB SUB_TYPE 1 to string, but not to byte[].

Jiri Cincura added a comment - 11/Apr/19 04:06 PM
SUB_TYPE 1 is text/string. Doesn't make sense with byte[].

The rest I don't understand. Unless I see some simple failing code, there's not much I can do.

Vladimir Karataev added a comment - 12/Apr/19 10:27 AM - edited
Why all operations with blob sub_type 1 as byte[] work fine, and only select is wrong? If SUB_TYPE 1 = text/string, than all operations should work with blob as string. An other hand, If SUB_TYPE 1 may be as byte[], than all oprations should work with blob as byte[]. Now I demonstrate mixed behavior with blob sub_type 1, when in some operations i can use byte[], and in select i can't use byte[].

Demo was be attached to ticket.

Jiri Cincura added a comment - 15/Apr/19 06:22 AM
Your mapping is wrong. You have the column as "BLOB SUB_TYPE 1", which is expected to be string. If you want to use "byte[]", use sub type 0.