Fix FinOps CPU right-sizing for Azure SQL Database (#735)

Lite.Tests/DismissedArchiveSidecarTests.cs

@@ -269,14 +269,14 @@ SELECT 1 FROM dismissed_archive_alerts d
     }
 
     [Fact]
-    public async Task SchemaVersion_IsUpdatedTo23()
+    public async Task SchemaVersion_IsUpdatedTo24()
     {
         using var connection = await InitializeDatabaseAsync();
 
         using var cmd = connection.CreateCommand();
         cmd.CommandText = "SELECT MAX(version) FROM schema_version";
         var version = Convert.ToInt32(await cmd.ExecuteScalarAsync(TestContext.Current.CancellationToken));
 
-        Assert.Equal(23, version);
+        Assert.Equal(DuckDbInitializer.CurrentSchemaVersion, version);
     }
 }

Lite/Analysis/DuckDbFactCollector.cs

@@ -1363,8 +1363,8 @@ private async Task CollectServerPropertiesFactsAsync(AnalysisContext context, Li
 
             using var cmd = connection.CreateCommand();
             cmd.CommandText = @"
-SELECT cpu_count, hyperthread_ratio, physical_memory_mb, socket_count, cores_per_socket,
-       is_hadr_enabled, edition, product_version
+SELECT COALESCE(vcore_count, cpu_count) AS cpu_count, hyperthread_ratio, physical_memory_mb,
+       socket_count, cores_per_socket, is_hadr_enabled, edition, product_version
 FROM server_properties
 WHERE server_id = $1
 ORDER BY collection_time DESC

Lite/Analysis/TestDataSeeder.cs

@@ -1525,7 +1525,8 @@ INSERT INTO trace_flags
     /// </summary>
     internal async Task SeedServerPropertiesAsync(int cpuCount, int htRatio,
         long physicalMemMb, int socketCount = 2, int coresPerSocket = 0,
-        bool hadrEnabled = false, string edition = "Standard Edition")
+        bool hadrEnabled = false, string edition = "Standard Edition",
+        int engineEdition = 2, string? serviceObjective = null, int? vcoreCount = null)
     {
         if (coresPerSocket == 0) coresPerSocket = cpuCount / (socketCount * 2); // assume HT
 
@@ -1539,9 +1540,10 @@ INSERT INTO server_properties
     (collection_id, collection_time, server_id, server_name,
      edition, product_version, product_level, engine_edition,
      cpu_count, hyperthread_ratio, physical_memory_mb,
-     socket_count, cores_per_socket, is_hadr_enabled)
-VALUES ($1, $2, $3, $4, $5, '16.0.4150.1', 'RTM', 2,
-        $6, $7, $8, $9, $10, $11)";
+     socket_count, cores_per_socket, is_hadr_enabled,
+     service_objective, vcore_count)
+VALUES ($1, $2, $3, $4, $5, '16.0.4150.1', 'RTM', $12,
+        $6, $7, $8, $9, $10, $11, $13, $14)";
 
         cmd.Parameters.Add(new DuckDBParameter { Value = _nextId-- });
         cmd.Parameters.Add(new DuckDBParameter { Value = TestPeriodEnd });
@@ -1554,6 +1556,9 @@ INSERT INTO server_properties
         cmd.Parameters.Add(new DuckDBParameter { Value = socketCount });
         cmd.Parameters.Add(new DuckDBParameter { Value = coresPerSocket });
         cmd.Parameters.Add(new DuckDBParameter { Value = hadrEnabled });
+        cmd.Parameters.Add(new DuckDBParameter { Value = engineEdition });
+        cmd.Parameters.Add(new DuckDBParameter { Value = (object?)serviceObjective ?? DBNull.Value });
+        cmd.Parameters.Add(new DuckDBParameter { Value = (object?)vcoreCount ?? DBNull.Value });
 
         await cmd.ExecuteNonQueryAsync();
     }
@@ -2034,6 +2039,28 @@ public async Task SeedBurstyCpuAsync()
         await SeedCpuUtilizationAlternatingAsync(low: 5, high: 85);
     }
 
+    /// <summary>
+    /// Scenario 11: Azure SQL DB vCore tier.
+    /// sys.dm_os_sys_info reports 20 cores (compute node total), but the database
+    /// is provisioned as HS_Gen5_14 (14 vCores). FinOps should use 14, not 20.
+    ///
+    /// Expected: CPU right-sizing uses vcore_count (14) instead of cpu_count (20).
+    /// </summary>
+    public async Task SeedAzureSqlDbVcoreAsync()
+    {
+        await ClearTestDataAsync();
+        await SeedTestServerAsync();
+
+        // Azure SQL DB: node has 20 cores, but this DB has HS_Gen5_14 (14 vCores)
+        // CPU at 8% avg — overprovisioned relative to 14 vCores
+        await SeedCpuUtilizationAsync(8, 2);
+        await SeedMemoryStatsAsync(totalPhysicalMb: 65_536, bufferPoolMb: 40_960, targetMb: 57_344);
+        await SeedServerPropertiesAsync(cpuCount: 20, htRatio: 1, physicalMemMb: 65_536,
+            edition: "SQL Azure", engineEdition: 5,
+            serviceObjective: "HS_Gen5_14", vcoreCount: 14);
+        await SeedFileSizeAsync(totalDataSizeMb: 51_200);
+    }
+
     // ============================================
     // Phase 3 Seed Helpers
     // ============================================

Lite/Database/DuckDbInitializer.cs

@@ -86,7 +86,7 @@ public void Dispose()
     /// <summary>
     /// Current schema version. Increment this when schema changes require table rebuilds.
     /// </summary>
-    internal const int CurrentSchemaVersion = 23;
+    internal const int CurrentSchemaVersion = 24;
 
     private readonly string _archivePath;
 
@@ -614,6 +614,20 @@ New tables only — no existing table changes needed. Tables created by
                 throw;
             }
         }
+
+        if (fromVersion < 24)
+        {
+            _logger?.LogInformation("Running migration to v24: adding vcore_count column to server_properties for Azure SQL DB vCore tracking");
+            try
+            {
+                await ExecuteNonQueryAsync(connection, "ALTER TABLE server_properties ADD COLUMN IF NOT EXISTS vcore_count INTEGER");
+            }
+            catch (Exception ex)
+            {
+                _logger?.LogError(ex, "Migration to v24 failed");
+                throw;
+            }
+        }
     }
 
     /// <summary>

Lite/Database/Schema.cs

@@ -642,7 +642,8 @@ CREATE TABLE IF NOT EXISTS server_properties (
     is_hadr_enabled BOOLEAN,
     is_clustered BOOLEAN,
     enterprise_features VARCHAR,
-    service_objective VARCHAR
+    service_objective VARCHAR,
+    vcore_count INTEGER
 )";
 
     public const string CreateServerPropertiesIndex = @"

Lite/Services/LocalDataService.FinOps.cs

@@ -345,7 +345,7 @@ GROUP BY server_id
     sp.product_level,
     sp.product_update_level,
     sp.engine_edition,
-    sp.cpu_count,
+    COALESCE(sp.vcore_count, sp.cpu_count) AS cpu_count,
     sp.physical_memory_mb,
     sp.socket_count,
     sp.cores_per_socket,
@@ -476,7 +476,7 @@ ORDER BY collection_time DESC
     LIMIT 1
 ),
 server_info AS (
-    SELECT cpu_count
+    SELECT COALESCE(vcore_count, cpu_count) AS cpu_count
     FROM v_server_properties
     WHERE server_id = $1
     ORDER BY collection_time DESC

Lite/Services/RemoteCollectorService.ServerProperties.cs

@@ -96,6 +96,15 @@ FROM sys.dm_os_sys_info AS osi
             bool? isClustered = reader.IsDBNull(12) ? null : reader.GetBoolean(12);
             var serviceObjective = reader.IsDBNull(13) ? null : reader.GetString(13);
 
+            /* For Azure SQL DB, sys.dm_os_sys_info.cpu_count returns the compute node's
+               total cores, not the per-database vCore allocation. Parse the actual vCore
+               count from the service_objective string (e.g. "HS_Gen5_14" → 14). */
+            int? vcoreCount = null;
+            if (isAzureSqlDb && !string.IsNullOrEmpty(serviceObjective))
+            {
+                vcoreCount = ParseVcoreFromServiceObjective(serviceObjective);
+            }
+
             sqlSw.Stop();
 
             var duckSw = Stopwatch.StartNew();
@@ -125,6 +134,7 @@ FROM sys.dm_os_sys_info AS osi
                        .AppendValue(isClustered)
                        .AppendValue((string?)null) // enterprise_features — not collected in Lite (requires cross-database cursor)
                        .AppendValue(serviceObjective)
+                       .AppendValue(vcoreCount)
                        .EndRow();
                     rowsCollected++;
                 }
@@ -143,4 +153,21 @@ FROM sys.dm_os_sys_info AS osi
         _logger?.LogDebug("Collected {RowCount} server properties row(s) for server '{Server}'", rowsCollected, server.DisplayName);
         return rowsCollected;
     }
+
+    /// <summary>
+    /// Parses the vCore count from an Azure SQL DB service objective string.
+    /// vCore tiers follow the pattern {Tier}_{Gen}_{VcoreCount}
+    /// (e.g. "HS_Gen5_14", "GP_Gen5_6", "BC_Gen5_8", "GP_S_Gen5_2").
+    /// DTU tiers (e.g. "P1", "S0") and elastic pools return null.
+    /// </summary>
+    internal static int? ParseVcoreFromServiceObjective(string serviceObjective)
+    {
+        var parts = serviceObjective.Split('_');
+        if (parts.Length >= 3 && int.TryParse(parts[^1], out var vcores) && vcores > 0)
+        {
+            return vcores;
+        }
+
+        return null;
+    }
 }