Deletes in one ARX transaction: roll back or commit

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

using ArxSamples.MySQL;
using ArxSamples.MySQL.Operations.DeleteMultiple.AdvancedCases;

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

await new Advanced1_DeleteInAnArxTransaction().RunAsync(new SampleContext(connectionString));

The sample, as it is in the repository.

using ARX.SDK.MySQL.Services;
using ARX.SDK.Services;
using static ArxSamples.MySQL.SampleOutput;

namespace ArxSamples.MySQL.Operations.DeleteMultiple.AdvancedCases;

/// <summary>
/// Deletes inside an ARX transaction, in two scenarios: delete, check, roll back (nothing is lost); and delete
/// several tables' rows and commit them together.
/// </summary>
public sealed class Advanced1_DeleteInAnArxTransaction : ISample
{
    public string Name => "delete-multiple-advanced-1-delete-in-an-arx-transaction";

    public string Title => "Deletes in one ARX transaction: roll back or commit";

    public async Task RunAsync(SampleContext dbContext)
    {
        // Three accounts per scenario: ACC-D701..703 survive scenario 1's rollback; scenario 2 deletes two of ACC-D711..713.
        await Scenario1_DeleteCheckRollBackAsync(dbContext, await CreateAccountsAsync(dbContext, 70));

        await Scenario2_DeleteAndCommitAsync(dbContext, await CreateAccountsAsync(dbContext, 71));
    }

    private static async Task<IReadOnlyList<ArxRecordId>> CreateAccountsAsync(SampleContext dbContext, int series)
    {
        var accounts = Enumerable.Range(1, 3).Select(i =>
        {
            var account = new ArxEntity("account");
            account["name"] = $"Transaction delete {series}{i}";
            account["account_number"] = $"ACC-D{series}{i}";
            return account;
        }).ToList();

        return await dbContext.Service.CreateMultipleAsync(accounts);
    }

    /// <summary>1. Delete three accounts, then your check says it was the wrong list: roll back and they're all back.</summary>
    private static async Task Scenario1_DeleteCheckRollBackAsync(SampleContext dbContext, IReadOnlyList<ArxRecordId> ids)
    {
        Step("1. Delete, check, roll back");

        await using var connection = new ArxMySqlConnection(dbContext.ConnectionString);
        await using var transaction = await connection.BeginTransactionAsync();

        var deleted = await dbContext.Service.DeleteMultipleAsync("account", ids, transaction);

        if (deleted != 2)
        {
            await transaction.RollbackAsync();
            Show($"expected 2, deleted {deleted}: rolled back");
        }

        /* ===========================================================
         * [DIRECT QUERY CHECK]
         * -----------------------------------------------------------
         * SELECT count(*)
         * FROM account
         * WHERE account_number IN ('ACC-D701', 'ACC-D702', 'ACC-D703');
         * -- Expect: 3: all back.
         * ===========================================================
         */
    }

    /// <summary>2. The right list this time, and a log entry for it: committed together.</summary>
    private static async Task Scenario2_DeleteAndCommitAsync(SampleContext dbContext, IReadOnlyList<ArxRecordId> ids)
    {
        Step("2. Delete and log, then commit");

        await using var connection = new ArxMySqlConnection(dbContext.ConnectionString);
        await using var transaction = await connection.BeginTransactionAsync();

        var deleted = await dbContext.Service.DeleteMultipleAsync("account", new[] { ids[0], ids[1] }, transaction);

        var log = new ArxEntity("activity_log");
        log["action"] = $"deleted {deleted} test accounts";
        await dbContext.Service.CreateAsync(log, transaction);

        await transaction.CommitAsync();
        Show($"{deleted} deleted and logged");

        /* ===========================================================
         * [DIRECT QUERY CHECK]
         * -----------------------------------------------------------
         * SELECT (SELECT count(*) FROM account WHERE account_number IN ('ACC-D711', 'ACC-D712', 'ACC-D713')) AS accounts,
         *        (SELECT count(*) FROM activity_log WHERE action = 'deleted 2 test accounts') AS logged;
         * -- Expect: 1, 1.
         * ===========================================================
         */
    }
}

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

namespace ArxSamples.MySQL;

/// <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 MySqlConnector 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.MySQL;

/// <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}");
}

The application's ARX service and its schema catalog, created once and shared by the samples.

using ARX.SDK.MySQL.Services;
using ARX.SDK.Services;

namespace ArxSamples.MySQL;

/// <summary>The application's ARX service and its schema catalog, shared by the real and advanced samples.</summary>
public sealed partial class SampleContext
{
    private ArxSchemaCatalog? _catalog;
    private ArxMySqlDbService? _service;

    /// <summary>The application's schema catalog: table ids, keys and selection sets (SampleCatalog.cs).</summary>
    public ArxSchemaCatalog Catalog => _catalog ??= SampleCatalog.Build();

    /// <summary>
    /// One service for the whole application. It holds no connection: every call opens one from the MySqlConnector pool and
    /// closes it, unless you pass your own connection or transaction.
    /// </summary>
    public ArxMySqlDbService Service => _service ??= new ArxMySqlDbService(ConnectionString, Catalog);
}

The application's schema catalog: every table's id column and keys, and its selection sets.

using ARX.SDK.Services;
using System.Text.Json;
using System.Text.Json.Serialization;

namespace ArxSamples.MySQL;

/// <summary>An account's industry. Stored in account.industry (SMALLINT) as the enum's number.</summary>
public enum Industry : short
{
    Retail = 1,
    Manufacturing = 2,
    Healthcare = 3,
    Finance = 4,
    Technology = 5
}

/// <summary>
/// The application's schema catalog: every table's id column and keys, and every picklist (selection set),
/// defined once.
/// </summary>
/// <remarks>
/// <para>
/// <b>Ids.</b> Every table the application writes is declared with its one id column: its name, its .NET type, and
/// whether the database generates it (<c>ArxIdColumn.Generated</c>: identity, sequence, default) or the caller supplies
/// it (<c>ArxIdColumn.Supplied</c>: a natural id, a client-generated Guid). A table with no id column, such as a log or a
/// table identified by several columns together, is declared <c>ArxIdColumn.NoIdColumn</c>. ARX never reads ids from
/// the database: the developer knows the schema, and an undeclared table is refused (ARX1016).
/// </para>
/// <para>
/// <b>Keys.</b> Optional business keys: one or more columns whose values identify a record, such as an account number,
/// or a region and a SKU together. Create doesn't use them (the database's unique constraints do the enforcing); Update
/// and Delete will be able to find rows by them. <c>ValidateSchemaAsync</c> checks ids and keys against the database
/// when you ask it to.
/// </para>
/// <para>
/// <b>Selection sets.</b> /// A selection set (picklist, option set) is a column that only accepts a fixed list of codes, each with a display
/// text: an account's status (ACTIVE, ON_HOLD, CLOSED), a contact's preferred channel (E, P, S). The catalog tells ARX,
/// for each set:
/// </para>
/// <list type="bullet">
/// <item><b>Name</b>: what an <see cref="ArxSelectionSetValue"/> refers to, for example <c>new ArxSelectionSetValue("AccountStatus", "ON_HOLD")</c>.</item>
/// <item><b>Kind</b>: what the codes are, matching the column: Integer, String, Character, Boolean, Decimal or Guid.
/// (A fixed list of text values is a String set, whether the column is an ENUM or a VARCHAR that a CHECK guards.)</item>
/// <item><b>Multiplicity</b>: Single (one code), or several codes stored as bit flags (Flags), a delimited string
/// (Delimited) or a JSON array (Json). MySQL has no array columns.</item>
/// <item><b>Options</b>: each code with its display text and order. A retired option (<c>IsActive: false</c>) stays
/// readable in old rows, but can't be written any more.</item>
/// </list>
/// <para>
/// Build the catalog once at startup and give it to the service: <c>new ArxMySqlDbService(connectionString, SampleCatalog.Build())</c>.
/// ARX checks every <see cref="ArxSelectionSetValue"/> against it in memory, before any SQL is sent, and stores the code
/// itself in the column: no lookup table, no extra query. A plain value (a string or number that isn't an
/// ArxSelectionSetValue) isn't checked.
/// </para>
/// <para>
/// The catalog is plain code, so the options can come from wherever you keep them: written out here, taken from a .NET
/// enum (<c>AddEnum</c>), loaded from JSON (<see cref="SetsJson"/> and <see cref="FromJson"/> below), or loaded at
/// startup from your own option table and passed to <c>new ArxSelectionSetDefinition(name, kind, options)</c>. ARX
/// never reads option tables or files itself.
/// </para>
/// </remarks>
public static class SampleCatalog
{
    /// <summary>
    /// Selection sets kept as JSON, as an application might keep them in a file, a settings store or a database column.
    /// Here the JSON is in the class itself; in an application, read it from wherever you keep it
    /// (<c>File.ReadAllText("selection-sets.json")</c>, configuration, an HTTP call) and pass it to <see cref="FromJson"/>.
    /// "multiplicity" and "active" are optional (Single and true).
    /// </summary>
    public const string SetsJson = """
        [
          {
            "name": "LeadSource",
            "kind": "String",
            "options": [
              { "value": "WEB",       "text": "Website",    "order": 0 },
              { "value": "REFERRAL",  "text": "Referral",   "order": 1 },
              { "value": "EVENT",     "text": "Trade show", "order": 2 },
              { "value": "COLD_CALL", "text": "Cold call",  "order": 3, "active": false }
            ]
          },
          {
            "name": "ContactRating",
            "kind": "Integer",
            "multiplicity": "Single",
            "options": [
              { "value": 1, "text": "Poor" },
              { "value": 2, "text": "Fair" },
              { "value": 3, "text": "Good" },
              { "value": 4, "text": "Very good" },
              { "value": 5, "text": "Excellent" }
            ]
          }
        ]
        """;

    public static ArxSchemaCatalog Build()
    {
        var builder = ArxSchemaCatalog.Create()

            // ---------- tables: id column and keys ----------
            // Generated BIGINT ids (AUTO_INCREMENT): the database fills them in. The keys are the unique columns that also
            // identify a record.
            .Table("account", ArxIdColumn.Generated<long>("id")).Key("account", "account_number")
            .Table("contact", ArxIdColumn.Generated<long>("id")).Key("contact", "email")

            // Retrieve: a contact's account_id reads back as a reference to its account, named by the account's
            // name; a contact is named by its first and last names.
            .Lookup("contact", "account_id", "account")
            .DisplayName("account", "name")
            .DisplayName("contact", new[] { "first_name", "last_name" }, " ")

            .Table("product_category", ArxIdColumn.Generated<long>("id")).Key("product_category", "name")
            .Table("product", ArxIdColumn.Generated<long>("id")).Key("product", "sku")
            .Table("sales_order", ArxIdColumn.Generated<long>("id")).Key("sales_order", "order_number")
            .Table("order_line", ArxIdColumn.Generated<long>("id"))
            .Table("data_type_showcase", ArxIdColumn.Generated<long>("id"))

            // A natural id: the caller gives the ISO country code.
            .Table("country", ArxIdColumn.Supplied<string>("code"))

            // A Guid id the application gives (CHAR(36)): MySQL can only hand back generated integer ids.
            .Table("device", ArxIdColumn.Supplied<Guid>("id")).Key("device", "serial_number")

            // No id column: a price is identified by its region and SKU together, a compound key.
            .Table("price_list", ArxIdColumn.NoIdColumn).Key("price_list", "region", "sku")

            // No primary key at all: the same action can be logged twice.
            .Table("activity_log", ArxIdColumn.NoIdColumn)

            // A table without an id: a visit is a fact, never updated (Retrieve Advanced8).
            .Table("web_visit", ArxIdColumn.NoIdColumn)

            // ---------- selection sets ----------

            // From a .NET enum: the set is named after the enum ("Industry"), the codes are its numbers (Retail = 1, …),
            // the display texts are its member names. Column: account.industry SMALLINT.
            .AddEnum<Industry>()

            // Written out: String codes with display texts, single choice. Column: account.status VARCHAR(10).
            .Add("AccountStatus", ArxSelectionSetKind.String, ("ACTIVE", "Active"), ("ON_HOLD", "On hold"), ("CLOSED", "Closed"))

            // Multiple choice, stored as delimited text ("ENTERPRISE,PUBLIC"). RESELLER is retired: rows that have it still
            // read back, but new writes can't use it. Column: account.segments VARCHAR(200).
            .Add(new ArxSelectionSetDefinition("CustomerSegment", ArxSelectionSetKind.String, new[]
            {
                new ArxSelectionSetOption("SMB", "Small business", 0),
                new ArxSelectionSetOption("ENTERPRISE", "Enterprise", 1),
                new ArxSelectionSetOption("PUBLIC", "Public sector", 2),
                new ArxSelectionSetOption("RESELLER", "Reseller", 3, IsActive: false)
            }, ArxSelectionSetMultiplicity.Delimited))

            // Single-character codes. Column: contact.preferred_channel CHAR(1).
            .Add("ContactChannel", ArxSelectionSetKind.Character, ('E', "Email"), ('P', "Phone"), ('S', "Text message"))

            // A fixed list of text values, in a MySQL ENUM column, which allows only its labels.
            // Column: data_type_showcase.mood ENUM('happy', 'neutral', 'sad').
            .Add(new ArxSelectionSetDefinition("Mood", ArxSelectionSetKind.String, new[]
            {
                new ArxSelectionSetOption("happy", "Happy", 0),
                new ArxSelectionSetOption("neutral", "Neutral", 1),
                new ArxSelectionSetOption("sad", "Sad", 2)
            }));

        // Loaded from JSON: LeadSource (contact.lead_source VARCHAR(50)) and ContactRating (contact.rating SMALLINT).
        foreach (var set in FromJson(SetsJson))
        {
            builder.Add(set);
        }

        return builder.Build();
    }

    /// <summary>Reads selection set definitions from JSON (the shape of <see cref="SetsJson"/>).</summary>
    public static IEnumerable<ArxSelectionSetDefinition> FromJson(string json)
    {
        var options = new JsonSerializerOptions
        {
            PropertyNameCaseInsensitive = true,
            Converters = { new JsonStringEnumConverter() }   // "String", "Integer", "Array", … as names
        };

        var sets = JsonSerializer.Deserialize<List<JsonSet>>(json, options)
            ?? throw new InvalidOperationException("The selection set JSON is empty.");

        foreach (var set in sets)
        {
            yield return new ArxSelectionSetDefinition(
                set.Name,
                set.Kind,
                set.Options.Select(x => new ArxSelectionSetOption(Code(x.Value, set.Kind), x.Text, x.Order, x.Active)),
                set.Multiplicity,
                set.DatabaseTypeName);
        }
    }

    /// <summary>A JSON value as a code of the set's kind: JSON has no char, Guid or 64-bit integer of its own.</summary>
    private static object Code(JsonElement value, ArxSelectionSetKind kind) => kind switch
    {
        ArxSelectionSetKind.Integer => value.GetInt64(),
        ArxSelectionSetKind.Decimal => value.GetDecimal(),
        ArxSelectionSetKind.Boolean => value.GetBoolean(),
        ArxSelectionSetKind.Guid => value.GetGuid(),
        ArxSelectionSetKind.Character => value.GetString()![0],
        _ => value.GetString()!   // String and DatabaseEnum
    };

    private sealed record JsonSet(
        string Name,
        ArxSelectionSetKind Kind,
        List<JsonOption> Options,
        ArxSelectionSetMultiplicity Multiplicity = ArxSelectionSetMultiplicity.Single,
        string? DatabaseTypeName = null);

    private sealed record JsonOption(JsonElement Value, string Text, int Order = 0, bool Active = true);
}

  > 1. Delete, check, roll back
      expected 2, deleted 3: rolled back
  > 2. Delete and log, then commit
      2 deleted and logged