sqlinsight-pro/tests/SQLInsight.Rules.Tests/IndexRuleTests.cs

using SQLInsight.Core.Data;
using SQLInsight.Core.Findings;
using SQLInsight.Rules.Engine;
using SQLInsight.Rules.Indexes;
using static SQLInsight.Rules.Tests.TestInstances;

namespace SQLInsight.Rules.Tests;

public class IndexRuleTests
{
    private static RuleResult Run(IRule rule, RuleContext context) => Assert.Single(new RuleEngine([rule]).Evaluate(context));

    private static IndexInfo Index(int id, string? name, string type, string[] keys, string[]? include = null, bool unique = false, bool pk = false,
        long reads = 100, long updates = 100, long pages = 1000, long rows = 100_000, long forwarded = 0, string table = "Orders") => new()
    {
        Schema = "dbo", Table = table, IndexId = id, Name = name, Type = type, KeyColumns = keys, IncludedColumns = include ?? [],
        IsUnique = unique || pk, IsPrimaryKey = pk, UserSeeks = reads, UserUpdates = updates, UsedPages = pages, Rows = rows, ForwardedFetches = forwarded,
    };

    private static RuleContext Indexes(TimeSpan uptime, IndexDatabase db) => With(new IndexSnapshot
    {
        CapturedAt = Now,
        SqlServerStartTime = Now.UtcDateTime - uptime,
        Databases = [db],
    });

    private static readonly TimeSpan Month = TimeSpan.FromDays(30);

    [Fact]
    public void Missing_index_suggests_create_with_equality_columns_first()
    {
        var db = new IndexDatabase
        {
            Name = "Sales",
            Indexes = [Index(1, "PK_Orders", "CLUSTERED", ["Id"], pk: true)],
            MissingIndexes = [new MissingIndex { Table = "[Sales].[dbo].[Orders]", EqualityColumns = "[CustomerId]", InequalityColumns = "[OrderDate]", IncludedColumns = "[Total]", Seeks = 50_000, Scans = 0, AverageTotalUserCost = 12, AverageUserImpact = 95 }],
        };

        var finding = Assert.Single(Run(new MissingIndexRule(), Indexes(Month, db)).Findings);

        Assert.Equal(Severity.Low, finding.Severity);
        Assert.Contains("CREATE INDEX [IX_Orders_CustomerId_OrderDate] ON [dbo].[Orders] ([CustomerId], [OrderDate]) INCLUDE ([Total]);", finding.FixScript, StringComparison.Ordinal);
    }

    [Fact]
    public void Missing_index_extends_an_existing_index_with_the_same_keys()
    {
        var db = new IndexDatabase
        {
            Name = "Sales",
            Indexes = [Index(1, "PK_Orders", "CLUSTERED", ["Id"], pk: true), Index(2, "IX_Orders_CustomerId", "NONCLUSTERED", ["CustomerId"], ["Status"])],
            MissingIndexes = [new MissingIndex { Table = "[Sales].[dbo].[Orders]", EqualityColumns = "[CustomerId]", IncludedColumns = "[Total]", Seeks = 100_000, Scans = 0, AverageTotalUserCost = 20, AverageUserImpact = 90 }],
        };

        var finding = Assert.Single(Run(new MissingIndexRule(), Indexes(Month, db)).Findings);

        Assert.Contains("Udvid det eksisterende index IX_Orders_CustomerId", finding.Recommendation, StringComparison.Ordinal);
        Assert.Contains("INCLUDE ([Status], [Total]) WITH (DROP_EXISTING = ON)", finding.FixScript, StringComparison.Ordinal);
    }

    [Fact]
    public void Missing_index_warns_about_write_heavy_table()
    {
        var db = new IndexDatabase
        {
            Name = "Sales",
            Indexes = [Index(1, "PK_Orders", "CLUSTERED", ["Id"], pk: true, reads: 10, updates: 1_000_000)],
            MissingIndexes = [new MissingIndex { Table = "[Sales].[dbo].[Orders]", EqualityColumns = "[CustomerId]", Seeks = 50_000, Scans = 0, AverageTotalUserCost = 12, AverageUserImpact = 95 }],
        };

        var finding = Assert.Single(Run(new MissingIndexRule(), Indexes(Month, db)).Findings);

        Assert.Contains(finding.Evidence, e => e.Value.Contains("skrives langt oftere", StringComparison.Ordinal));
    }

    [Fact]
    public void Small_missing_index_suggestion_is_ignored()
    {
        var db = new IndexDatabase
        {
            Name = "Sales",
            MissingIndexes = [new MissingIndex { Table = "[Sales].[dbo].[Orders]", EqualityColumns = "[CustomerId]", Seeks = 50, Scans = 0, AverageTotalUserCost = 0.5, AverageUserImpact = 40 }],
        };

        Assert.Equal(RuleOutcome.Passed, Run(new MissingIndexRule(), Indexes(Month, db)).Outcome);
    }

    [Fact]
    public void Unused_index_needs_seven_days_of_uptime()
    {
        var db = new IndexDatabase { Name = "Sales", Indexes = [Index(2, "IX_Unused", "NONCLUSTERED", ["Status"], reads: 0, updates: 50_000)] };

        Assert.Equal(RuleOutcome.NotMeasurable, Run(new UnusedIndexRule(), Indexes(TimeSpan.FromDays(2), db)).Outcome);
        var finding = Assert.Single(Run(new UnusedIndexRule(), Indexes(Month, db)).Findings);
        Assert.Contains("DISABLE", finding.FixScript, StringComparison.Ordinal);
    }

    [Fact]
    public void Unique_and_primary_key_indexes_are_never_unused_candidates()
    {
        var db = new IndexDatabase
        {
            Name = "Sales",
            Indexes = [Index(2, "UX_Code", "NONCLUSTERED", ["Code"], unique: true, reads: 0, updates: 50_000), Index(1, "PK", "CLUSTERED", ["Id"], pk: true, reads: 0, updates: 50_000)],
        };

        Assert.Equal(RuleOutcome.Passed, Run(new UnusedIndexRule(), Indexes(Month, db)).Outcome);
    }

    [Theory]
    [InlineData(new[] { "A" }, new string[0], new[] { "A" }, new string[0], true)]           // exact duplicate
    [InlineData(new[] { "A", "B" }, new string[0], new[] { "A" }, new string[0], true)]      // left prefix
    [InlineData(new[] { "A", "B" }, new[] { "C" }, new[] { "A" }, new[] { "C" }, true)]       // include covered by include
    [InlineData(new[] { "A", "B" }, new string[0], new[] { "A" }, new[] { "B" }, true)]       // include covered by key
    [InlineData(new[] { "A", "B" }, new string[0], new[] { "A" }, new[] { "C" }, false)]      // include not covered
    [InlineData(new[] { "B", "A" }, new string[0], new[] { "A" }, new string[0], false)]      // not a leading prefix
    public void Covers(string[] coverKeys, string[] coverInclude, string[] candidateKeys, string[] candidateInclude, bool expected)
    {
        var cover = Index(2, "IX_Cover", "NONCLUSTERED", coverKeys, coverInclude);
        var candidate = Index(3, "IX_Candidate", "NONCLUSTERED", candidateKeys, candidateInclude);

        Assert.Equal(expected, DuplicateIndexRule.Covers(cover, candidate));
    }

    [Fact]
    public void Unique_index_is_not_covered_by_a_wider_index()
    {
        Assert.False(DuplicateIndexRule.Covers(Index(2, "IX_Wide", "NONCLUSTERED", ["A", "B"]), Index(3, "UX_A", "NONCLUSTERED", ["A"], unique: true)));
    }

    [Fact]
    public void Filtered_indexes_only_cover_the_same_filter()
    {
        var filtered = Index(2, "IX_Active", "NONCLUSTERED", ["A"]) with { Filter = "([Active]=(1))" };

        Assert.False(DuplicateIndexRule.Covers(filtered, Index(3, "IX_A", "NONCLUSTERED", ["A"])));
    }

    [Fact]
    public void Duplicate_rule_reports_each_pair_once()
    {
        var db = new IndexDatabase
        {
            Name = "Sales",
            Indexes =
            [
                Index(1, "PK_Orders", "CLUSTERED", ["Id"], pk: true),
                Index(2, "IX_A", "NONCLUSTERED", ["CustomerId"]),
                Index(3, "IX_B", "NONCLUSTERED", ["CustomerId"]),
            ],
        };

        var finding = Assert.Single(Run(new DuplicateIndexRule(), Indexes(Month, db)).Findings);

        Assert.Equal(Severity.Medium, finding.Severity);
    }

    [Fact]
    public void Heap_with_many_forwarded_fetches()
    {
        var db = new IndexDatabase { Name = "Sales", Indexes = [Index(0, null, "HEAP", [], forwarded: 250_000)] };

        var finding = Assert.Single(Run(new ForwardedRecordsRule(), Indexes(Month, db)).Findings);

        Assert.Contains("ALTER TABLE [dbo].[Orders] REBUILD;", finding.FixScript, StringComparison.Ordinal);
    }

    [Fact]
    public void Stale_statistics_on_large_tables_only()
    {
        var db = new IndexDatabase
        {
            Name = "Sales",
            Statistics =
            [
                new StatisticInfo { Schema = "dbo", Table = "Orders", Name = "IX_Orders_Date", Rows = 1_000_000, Modifications = 400_000 },
                new StatisticInfo { Schema = "dbo", Table = "Small", Name = "PK_Small", Rows = 500, Modifications = 500 },
                new StatisticInfo { Schema = "dbo", Table = "Stable", Name = "PK_Stable", Rows = 1_000_000, Modifications = 1_000 },
            ],
        };

        var finding = Assert.Single(Run(new StaleStatisticsRule(), Indexes(Month, db)).Findings);

        Assert.Equal("statistic: Sales.dbo.Orders.IX_Orders_Date", finding.Subject);
    }

    [Fact]
    public void Auto_statistics_off()
    {
        var off = Database(change: d => d with { IsAutoUpdateStatistics = false });

        var finding = Assert.Single(Run(new AutoStatisticsRule(), With(DatabaseList(off))).Findings);

        Assert.Equal("ALTER DATABASE [Sales] SET AUTO_UPDATE_STATISTICS ON;", finding.FixScript);
    }
}