在 Entity Framework Core 中为 PostgreSQL 表的计算列设置公式

Question

I have a simple model with Id and a json property and a computed column which is value of 'tile' key in the json column

public class Book 
{
    public int Id { get; set; }

    [Column(TypeName="jsonb")]
    public string JsonInfo { get; set; }

    [DatabaseGenerated(DatabaseGeneratedOption.Computed)]
    public string Title { get; set; }
}

in the configuration I set the way which the value of Title is caculated:

    builder.Property(t => t.Title).HasComputedColumnSql("(\"JsonInfo\"->>''title'')", stored:true).HasColumnType("varchar(150)");

the migration is build without problem, but unfortunately the database update ends with an error:

42601: syntax error at or near "title"

The problem is within the "(\\"JsonInfo\\"->>''title'')" that how the title is escaped. How can i fix it?

Just to mention, i use latest version of PostgreSQL

Answer 1

You shouldn't be escaping the title with twice single-quotes; the SQL you give to HasComputedColumnSql isn't a text literal, it's actual SQL. So the following should work:

.HasComputedColumnSql("\"JsonInfo\"->>'title'", stored: true)