Delete on a preloaded schema: keys only, Strict

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

using ArxSamples.PostgreSql;
using ArxSamples.PostgreSql.Operations.Delete.AdvancedCases;

// 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 Advanced3_DynamicTableSchemaServiceSetup().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.AdvancedCases;

/// <summary>
/// Delete on a schema preloaded at service setup, in three scenarios: the convenient setup (keys only)
/// deleting by the key the preload found, with the table it added because it is referenced; Strict refusing a delete
/// matched by a column that wasn't preloaded; and the same delete on a service that isn't Strict.
/// </summary>
/// <remarks>
/// Under Strict, every column that finds the rows to delete must be preloaded, so an endpoint can only delete by the
/// columns you chose. Create Advanced6 shows the preload itself and its JSON.
/// </remarks>
public sealed class Advanced3_DynamicTableSchemaServiceSetup : ISample
{
    public string Name => "delete-advanced-3-dynamic-table-schema-service-setup";

    public string Title => "Delete on a preloaded schema: keys only, Strict";

    public async Task RunAsync(SampleContext dbContext)
    {
        foreach (var (first, email) in new[] { ("Dora", "dora.delete@example.com"), ("Dev", "dev.delete@example.com"), ("Dee", "dee.delete@example.com") })
        {
            var contact = new ArxEntity("contact");
            contact["first_name"] = first;
            contact["last_name"] = "Deleteme";
            contact["email"] = email;
            await dbContext.Service.CreateAsync(contact);
        }

        await Scenario1_DeleteByTheKeyThePreloadFoundAsync(dbContext);

        await Scenario2_StrictRefusesAColumnNotPreloadedAsync(dbContext);

        await Scenario3_NotStrictTheSameDeleteWorksAsync(dbContext);
    }

    /// <summary>1. Keys only: contact.email is unique, so it is a key; account comes too (contact.account_id references it).</summary>
    private static async Task Scenario1_DeleteByTheKeyThePreloadFoundAsync(SampleContext dbContext)
    {
        Step("1. KeysOnly: delete by the key the preload found");

        var tables = new ArxPreLoadTableRegister()
            .PreLoadTable("contact");

        var schema = await new ArxPreLoadTable(tables, ArxPreLoadMode.KeysOnly).LoadAsync(dbContext.ConnectionString);
        var service = new ArxPgDbService(dbContext.ConnectionString, schema);

        foreach (var table in schema.Tables)
        {
            Show($"{table.Name,-8} {table.Reason}; keys {string.Join(" ", table.Keys)}");
        }

        var dora = new ArxEntity("contact");
        dora["email"] = "dora.delete@example.com";
        Show($"deleted {await service.DeleteAsync(dora, new ArxDeleteOptions { Match = ArxMatch.Key("email") })} row");

        /* ===========================================================
         * [DIRECT QUERY CHECK]
         * -----------------------------------------------------------
         * SELECT count(*)
         * FROM contact
         * WHERE email = 'dora.delete@example.com';
         * -- Expect: 0.
         * ===========================================================
         */
    }

    /// <summary>2. Strict with only email preloaded: deleting every contact named "Deleteme" is refused before the database.</summary>
    private static async Task Scenario2_StrictRefusesAColumnNotPreloadedAsync(SampleContext dbContext)
    {
        Step("2. Strict: a delete matched by a column that wasn't preloaded");

        var tables = new ArxPreLoadTableRegister()
            .PreLoadTable("contact", ["email"]);

        var schema = await new ArxPreLoadTable(tables).LoadAsync(dbContext.ConnectionString);
        var strict = new ArxPgDbService(dbContext.ConnectionString, schema) { Strict = true };

        var byLastName = new ArxEntity("contact");
        byLastName["last_name"] = "Deleteme";

        try
        {
            await strict.DeleteAsync(byLastName, new ArxDeleteOptions { Match = ArxMatch.Columns("last_name") });
        }
        catch (ArxValidationException exception) when (exception.Code == ArxErrorCode.NotPreloaded)
        {
            ShowError(exception);
        }

        var byEmail = new ArxEntity("contact");
        byEmail["email"] = "dev.delete@example.com";
        Show($"by the preloaded email: deleted {await strict.DeleteAsync(byEmail, new ArxDeleteOptions { Match = ArxMatch.Key("email") })} row");

        /* ===========================================================
         * [DIRECT QUERY CHECK]
         * -----------------------------------------------------------
         * SELECT email
         * FROM contact
         * WHERE last_name = 'Deleteme';
         * -- Expect: 1 row, dee.delete@example.com: the delete by last_name was refused, dev's by email ran.
         * ===========================================================
         */
    }

    /// <summary>3. The same schema, not Strict: last_name isn't preloaded, and the delete by it still works.</summary>
    private static async Task Scenario3_NotStrictTheSameDeleteWorksAsync(SampleContext dbContext)
    {
        Step("3. Not Strict: the same delete works");

        var tables = new ArxPreLoadTableRegister()
            .PreLoadTable("contact", ["email"]);

        var schema = await new ArxPreLoadTable(tables).LoadAsync(dbContext.ConnectionString);
        var service = new ArxPgDbService(dbContext.ConnectionString, schema);

        var byLastName = new ArxEntity("contact");
        byLastName["last_name"] = "Deleteme";
        Show($"deleted {await service.DeleteAsync(byLastName, new ArxDeleteOptions { Match = ArxMatch.Columns("last_name") })} row");

        /* ===========================================================
         * [DIRECT QUERY CHECK]
         * -----------------------------------------------------------
         * SELECT count(*)
         * FROM contact
         * WHERE last_name = 'Deleteme';
         * -- Expect: 0.
         * ===========================================================
         */
    }
}

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}");
}

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

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

namespace ArxSamples.PostgreSql;

/// <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 ArxPgDbService? _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 Npgsql pool and
    /// closes it, unless you pass your own connection or transaction.
    /// </summary>
    public ArxPgDbService Service => _service ??= new ArxPgDbService(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.PostgreSql;

/// <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, Guid, or a
/// PostgreSQL enum type (DatabaseEnum).</item>
/// <item><b>Multiplicity</b>: Single (one code), or several codes stored as an array (Array), bit flags (Flags), a
/// delimited string (Delimited) or a JSON array (Json).</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 ArxPgDbService(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 (bigserial): 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 generated uuid id (DEFAULT gen_random_uuid()).
            .Table("device", ArxIdColumn.Generated<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 partitioned 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 text.
            .Add("AccountStatus", ArxSelectionSetKind.String, ("ACTIVE", "Active"), ("ON_HOLD", "On hold"), ("CLOSED", "Closed"))

            // Multiple choice, stored as an array of codes. RESELLER is retired: rows that have it still read back,
            // but new writes can't use it. Column: account.segments text[].
            .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.Array))

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

            // The labels of a PostgreSQL enum type: the value is written with a cast to that type.
            // Column: data_type_showcase.mood showcase_mood.
            .Add(new ArxSelectionSetDefinition("Mood", ArxSelectionSetKind.DatabaseEnum, new[]
            {
                new ArxSelectionSetOption("happy", "Happy", 0),
                new ArxSelectionSetOption("neutral", "Neutral", 1),
                new ArxSelectionSetOption("sad", "Sad", 2)
            }, databaseTypeName: "showcase_mood"));

        // Loaded from JSON: LeadSource (contact.lead_source text) 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. KeysOnly: delete by the key the preload found
      contact  requested; keys (email)
      account  added: referenced by contact.account_id; keys (account_number)
      deleted 1 row
  > 2. Strict: a delete matched by a column that wasn't preloaded
      caught ArxValidationException: ARX1018 NotPreloaded: Column 'last_name' of 'contact' wasn't preloaded, and the service is Strict. Preloaded: id, email. Add it to the ArxPreLoadTable, or turn Strict off.
      by the preloaded email: deleted 1 row
  > 3. Not Strict: the same delete works
      deleted 1 row