Expose a catalog

Functions are callable, but a catalog lets the worker look like a database: users can query plain tables, inspect schemas and constraints, and use worker-defined views and macros.

CatalogExample.cs

using QueryFarm.Vgi.Catalog;
using QueryFarm.Vgi.Protocol;

namespace QueryFarm.Vgi.DocsExamples;

public static class CatalogExample
{
    public static void Register(Worker worker, NumbersFunction numbers)
    {
        worker.RegisterCatalogTable(new CatalogTable
        {
            Name = "first_five",
            SchemaName = "catalog",
            Comment = "The integers zero through four",
            ScanFunction = numbers,
            ScanArguments = [5L],
        });

        worker.RegisterView(new CatalogView
        {
            Name = "evens",
            SchemaName = "catalog",
            Definition = "SELECT * FROM first_five WHERE n % 2 = 0",
            Comment = "Even values from catalog.first_five",
        });

        worker.RegisterMacro(new CatalogMacro
        {
            Name = "triple",
            SchemaName = "catalog",
            MacroType = MacroType.Scalar,
            Definition = "value * 3",
            Parameters = ["value"],
            Comment = "Multiply a value by three",
        });
    }
}

CatalogTable.ScanFunction is the recommended table shape. Its output schema is reused as the table columns unless Columns is set explicitly, and ScanArguments / ScanNamedArguments bind fixed values for that table.

SELECT * FROM demo.catalog.first_five;
SELECT * FROM demo.catalog.evens;
SELECT demo.catalog.triple(7);

CatalogTable can additionally declare comments, tags, defaults, generated columns, primary and foreign keys, required filters, statistics, row IDs, writable handlers, time travel, or multi-branch scans. Keep declarations internally consistent: a constraint names the table’s published columns, and an advertised write operation needs the matching table-in/out function.

Registration also exposes the scan function

RegisterCatalogTable registers its ScanFunction as a callable table function. Do not separately register the same instance under the same schema and name, or DuckDB will see duplicate overloads.