Delete without a catalog

Runs the sample. Generated for this page; it reads the connection string from the environment.

using ArxSamples.PostgreSql;
using ArxSamples.PostgreSql.Operations.Delete.Basics;

// The connection string comes from the environment, never from the code (see "Configure the connection").
var connectionString = Environment.GetEnvironmentVariable("ARX_SAMPLES_POSTGRESQL")
    ?? throw new InvalidOperationException("Set the ARX_SAMPLES_POSTGRESQL environment variable to your PostgreSQL connection string.");

await new Basic4_WithoutACatalog().RunAsync(new SampleContext(connectionString));

The sample, as it is in the repository.

using ARX.SDK;
using ARX.SDK.PostgreSql.Services;
using ARX.SDK.Services;

using static ArxSamples.PostgreSql.SampleOutput;

namespace ArxSamples.PostgreSql.Operations.Delete.Basics;

/// <summary>
/// Deletes on a service created with only a connection string, in three scenarios: by the id, read from the table's
/// primary key; a table with no primary key, by columns; and the same table by an id, refused with ARX1019 before
/// anything is deleted.
/// </summary>
/// <remarks>
/// <para>Every call reads its table from the database first, which makes it much slower than a service with a catalog
/// (Create Basic6 says when that is fine).</para>
/// </remarks>
public sealed class Basic4_WithoutACatalog : ISample
{
    public string Name => "delete-basics-4-without-a-catalog";

    public string Title => "Delete without a catalog";

    public async Task RunAsync(SampleContext dbContext)
    {
        var service = new ArxPgDbService(dbContext.ConnectionString);

        await Scenario1_ByTheIdAsync(service);

        await Scenario2_ATableWithNoPrimaryKey_ByColumnsAsync(service);

        await Scenario3_ATableWithNoPrimaryKey_ByAnIdAsync(service);
    }

    /// <summary>1. The usual way: the table and the id Create returned.</summary>
    private static async Task Scenario1_ByTheIdAsync(ArxPgDbService service)
    {
        Step("1. By the id");

        var account = new ArxEntity("account");
        account["name"] = "Woodgrove Bank";
        account["account_number"] = "ACC-N041";
        ArxRecordId id = await service.CreateAsync(account);

        bool deleted = await service.DeleteAsync("account", id);

        Show($"account {id.AsInt64()} deleted: {deleted}");

        /* ===========================================================
         * [DIRECT QUERY CHECK]
         * -----------------------------------------------------------
         * SELECT count(*)
         * FROM account
         * WHERE account_number = 'ACC-N041';
         * -- Expect: 0.
         * ===========================================================
         */
    }

    /// <summary>2. activity_log has no primary key: find the rows by a column, and every matching row goes.</summary>
    private static async Task Scenario2_ATableWithNoPrimaryKey_ByColumnsAsync(ArxPgDbService service)
    {
        Step("2. A table with no primary key, by columns");

        for (var i = 0; i < 2; i++)
        {
            var entry = new ArxEntity("activity_log") { IdColumn = ArxIdColumn.NoIdColumn };
            entry["action"] = "opened the trial";
            await service.CreateAsync(entry);
        }

        var match = new ArxEntity("activity_log");
        match["action"] = "opened the trial";

        int deleted = await service.DeleteAsync(match, new ArxDeleteOptions { Match = ArxMatch.Columns("action") });

        Show($"{deleted} log entries deleted");

        /* ===========================================================
         * [DIRECT QUERY CHECK]
         * -----------------------------------------------------------
         * SELECT count(*)
         * FROM activity_log
         * WHERE action = 'opened the trial';
         * -- Expect: 0.
         * ===========================================================
         */
    }

    /// <summary>3. By an id on that table: there is no id column to find it by, so ARX1019, and nothing is deleted.</summary>
    private static async Task Scenario3_ATableWithNoPrimaryKey_ByAnIdAsync(ArxPgDbService service)
    {
        Step("3. A table with no primary key, by an id");

        try
        {
            await service.DeleteAsync("activity_log", 1L);
        }
        catch (ArxValidationException error) when (error.Code == ArxErrorCode.TableNotResolvable)
        {
            Show($"refused: {error.Message}");
        }

        /* ===========================================================
         * [DIRECT QUERY CHECK]
         * -----------------------------------------------------------
         * SELECT count(*)
         * FROM activity_log;
         * -- Expect: the same count as before the call.
         * ===========================================================
         */
    }
}

What every sample is given: the connection string (and the ISample interface the samples implement).

namespace ArxSamples.PostgreSql;

/// <summary>One documentation sample: a scenario a real application has, shown end to end.</summary>
public interface ISample
{
    /// <summary>The name to run it alone: <c>dotnet run -- &lt;name&gt;</c>.</summary>
    string Name { get; }

    /// <summary>One line on what it shows.</summary>
    string Title { get; }

    Task RunAsync(SampleContext dbContext);
}

/// <summary>
/// What a sample is given. Every sample gets the connection string; the application's service and catalog
/// (SampleContext.Application.cs) and the plain Npgsql read-back helper (SampleContext.Direct.cs) live in their own
/// files, so a sample needs only the files it uses.
/// </summary>
public sealed partial class SampleContext
{
    public SampleContext(string connectionString)
    {
        ConnectionString = connectionString;
    }

    public string ConnectionString { get; }
}

How the samples print: Step for each scenario, Show for what it did, ShowError for an error caught on purpose.

using ARX.SDK;

namespace ArxSamples.PostgreSql;

/// <summary>How the samples print: a numbered step for each scenario, then what it did.</summary>
public static class SampleOutput
{
    /// <summary>The start of a scenario: <c>Step("1. By the id Create returned")</c>.</summary>
    public static void Step(string text) => Console.WriteLine($"  > {text}");

    /// <summary>What the scenario did.</summary>
    public static void Show(string text) => Console.WriteLine($"      {text}");

    /// <summary>An ARX error the scenario caught on purpose.</summary>
    public static void ShowError(ArxException exception)
        => Console.WriteLine($"      caught {exception.GetType().Name}: {exception.Message}");
}

  > 1. By the id
      account 1 deleted: True
  > 2. A table with no primary key, by columns
      2 log entries deleted
  > 3. A table with no primary key, by an id
      refused: ARX1019 TableNotResolvable: Can't resolve table 'activity_log': it has no primary key, so there is no id for this call to use. Declare it in a schema catalog with .Table("activity_log", ArxIdColumn.NoIdColumn) (Create then returns ArxRecordId.None), find its rows by a key or columns (ArxMatch.Key, ArxMatch.Columns), or give it a primary key.