ts_vector_update_trigger与postgresql / npgsql + EFCore中的JSONB列

Question

In EFCore + npgsql, using postgresql 10, I want to create a tsvector column to allow full text search of some fields in a model:

public class MyModel
{
  public string Title { get; set; }

  public string Description { get; set; }

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

I want the full text search to include values from the JSONB column, so as according to the npgsql docs I update my model like so:

public class MyModel
{
  public string Title { get; set; }

  public string Description { get; set; }

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

  public NpgsqlTsVector SearchVector { get; set; }
}

add the following index in OnModelCreating in my DB context:

  modelBuilder.Entity<MyModel>(m =>
  {
    // create some other indexes
    m.HasIndex(e => new { e.SearchVector }).ForNpgsqlHasMethod("GIN");
  });

Then create the migration and edit (in accordance with docs) to get the following methods:

protected override void Up(MigrationBuilder migrationBuilder)
{
  migrationBuilder.AddColumn<NpgsqlTsVector>(
    name: "SearchVector",
    table: "MyModels",
    nullable: true);

  migrationBuilder.CreateIndex(
    name: "IX_MyModels_SearchVector",
    table: "MyModels",
    column: "SearchVector")
    .Annotation("Npgsql:IndexMethod", "GIN");

  migrationBuilder.Sql(
    @"CREATE TRIGGER my_model_search_vector_update BEFORE INSERT OR UPDATE
    ON ""MyModels"" FOR EACH ROW EXECUTE PROCEDURE
    tsvector_update_trigger(""SearchVector"", 'pg_catalog.english', ""Title"", ""Description"", ""JSON"");");

  // I am updating an existing table, so:
  migrationBuilder.Sql("UPDATE \"MyModels\" SET \"Title\" = \"Title\";");
}

protected override void Down(MigrationBuilder migrationBuilder)
{
  migrationBuilder.DropIndex(
    name: "IX_MyModels_SearchVector",
    table: "MyModels");

  migrationBuilder.DropColumn(
    name: "SearchVector",
    table: "MyModels");

  migrationBuilder.Sql("DROP TRIGGER my_model_search_vector_update");
}

But after all this, when applying Update-Database, I see:

Failed executing DbCommand (50ms) [Parameters=[], CommandType='Text', CommandTimeout='30']
UPDATE "MyModels" SET "Title" = "Title";
Npgsql.PostgresException: column "JSON" is not of a character type

I assume this is because the JSONB column is binary data. Is it possible to achieve what I'm looking for? I'm relatively new to postgresql, npgsql and EFCore.

Answer 1

I'm pretty sure you can't do full-text search over PostgreSQL jsonb because, as you wrote, it's not a text type. There's a small change that using json would work - as that's textual storage - but that type is much closer to simple text and doesn't offer many of the advantages of binary jsonb .

However, depending on exactly what you want to do, jsonb has quite a lot of search functionality (with SQL/JSON JSONPATH also coming in PostgreSQL 12). This functionality isn't currently mapped in EF Core, but that shouldn't really stop you from using it via raw SQL.