EF.Functions.Match translates to faulty sql

Steps to reproduce

Standard asp.net core mvc application.

Entity Class

public class DocumentFileEntity : BaseEntity
{
    ...
    public String? Text { get; set; }
    ...
}

The issue

Using the Function EF.Functions.Match in a Linq-Where Statement leads to non executable SQL.

The used Linq-Query is:

List<DocumentEntity> documentEntities = await this.dbContext.DocumentFiles
   .Where(documentFile => EF.Functions.Match("Text", searchTerm, MySqlMatchSearchMode.NaturalLanguage))
   .Select(documentFile => documentFile.Document)
   .ToListAsync();

Generated SQL and Exception

fail: Microsoft.EntityFrameworkCore.Database.Command[20102]
      Failed executing DbCommand (5ms) [Parameters=[@__searchTerm_1='?' (Size = 4000)], CommandType='Text', CommandTimeout='30']
      SELECT `d0`.`Id`, `d0`.`FolderId`, `d0`.`Name`, `d0`.`Type`
      FROM `DocumentFiles` AS `d`
      INNER JOIN `Documents` AS `d0` ON `d`.`DocumentId` = `d0`.`Id`
      WHERE MATCH ('Text') AGAINST (@__searchTerm_1)
fail: Microsoft.EntityFrameworkCore.Query[10100]
      An exception occurred while iterating over the results of a query for context type 'Flek.Data.ApplicationDbContext'.
      MySqlConnector.MySqlException (0x80004005): You have an error in your SQL syntax; check the manual that corresponds to your MariaDB server version for the right syntax to use near ''Text') AGAINST ('a')' at line 4

It looks to me like the single quotes around the column name ‘Text’ name are the problem. A related PR that i found is #1268.

Further technical details

Pomelo.EntityFrameworkCore.MySql version: 6.0.1 Microsoft.AspNetCore.App version: .NET 6

[federicofz85]

@lauxjpn Hi guys is there a way to match with 2 or more properties? I noticed that there’s a overload that asks for string[] properties but I can’t make it work. I already have the index but I’m getting System.InvalidOperationException: Expression ‘@__test_3’ in the SQL tree does not have a type mapping assigned.

Found it! new[] { x.Col1, x.Col2, x.Col3 } Thanks!

[lauxjpn]

I’ve never seen this notation before. I would have expected that when passing object.Property on a string parameter, the value of the property would be passed, and then that the string value of the property would have been used as column name.

@RSBlek No problem. Your EF Core LINQ queries are actually not C# code that is being executed. Instead, they are expression trees that describe the operations that you have typed.

If e.g. you have a documentFile.Size + 42 operation in your LINQ query (for whatever reason), then EF Core and Pomelo will receive an Expression object that has a Left property that is set to another expression representing your documentFile.Size property, a Right property that is set to another expression representing the constant value 42, and a NodeType property that is set to Add (which is the operation that should be applied to the two properties/operands).

So what EF Core and Pomelo do, is basically just to parse this expression tree and convert all the expressions to SQL in a way that makes sense.

See Expression Trees (C#) for more general information.