fix(site-event-logging): resolve SiteEventLogging-006,009,011 — severity index, accurate XML doc, dead-placeholder removal

tests/ScadaLink.SiteEventLogging.Tests/SchemaIndexTests.cs

@@ -0,0 +1,68 @@
+using Microsoft.Data.Sqlite;
+using Microsoft.Extensions.Logging.Abstractions;
+using Microsoft.Extensions.Options;
+
+namespace ScadaLink.SiteEventLogging.Tests;
+
+/// <summary>
+/// Regression tests for SiteEventLogging-006: the schema must index the columns the
+/// query service filters on so common queries do not full-scan a 1 GB database.
+/// </summary>
+public class SchemaIndexTests : IDisposable
+{
+    private readonly SiteEventLogger _logger;
+    private readonly SqliteConnection _verifyConnection;
+    private readonly string _dbPath;
+
+    public SchemaIndexTests()
+    {
+        _dbPath = Path.Combine(Path.GetTempPath(), $"test_index_{Guid.NewGuid()}.db");
+        var options = Options.Create(new SiteEventLogOptions { DatabasePath = _dbPath });
+        _logger = new SiteEventLogger(options, NullLogger<SiteEventLogger>.Instance);
+
+        _verifyConnection = new SqliteConnection($"Data Source={_dbPath}");
+        _verifyConnection.Open();
+    }
+
+    public void Dispose()
+    {
+        _verifyConnection.Dispose();
+        _logger.Dispose();
+        if (File.Exists(_dbPath)) File.Delete(_dbPath);
+    }
+
+    [Fact]
+    public void Schema_HasIndexOnSeverity()
+    {
+        using var cmd = _verifyConnection.CreateCommand();
+        cmd.CommandText =
+            "SELECT name FROM sqlite_master WHERE type = 'index' AND tbl_name = 'site_events'";
+        var indexes = new List<string>();
+        using var reader = cmd.ExecuteReader();
+        while (reader.Read()) indexes.Add(reader.GetString(0));
+
+        Assert.Contains("idx_events_severity", indexes);
+    }
+
+    [Fact]
+    public async Task SeverityFilteredQuery_UsesIndex_NotFullScan()
+    {
+        await _logger.LogEventAsync("script", "Error", null, "S", "boom");
+        await _logger.LogEventAsync("script", "Info", null, "S", "ok");
+
+        using var cmd = _verifyConnection.CreateCommand();
+        cmd.CommandText =
+            "EXPLAIN QUERY PLAN SELECT id FROM site_events WHERE severity = 'Error'";
+        var plan = new System.Text.StringBuilder();
+        using var reader = cmd.ExecuteReader();
+        while (reader.Read())
+        {
+            // The detail column holds the human-readable plan step.
+            plan.Append(reader.GetString(reader.GetOrdinal("detail"))).Append('\n');
+        }
+
+        var planText = plan.ToString();
+        Assert.Contains("idx_events_severity", planText);
+        Assert.DoesNotContain("SCAN site_events", planText);
+    }
+}