Update StatsSampled/RowsSampled columns during maintenance

Author: sergiisyrovatchenko

Server/Query.cs

@@ -721,6 +721,55 @@ FROM sys.partitions WITH(NOLOCK)
      , RowsCount        = ISNULL(@RowsCount, 0)
      , IndexStats       = DATEADD(MINUTE, -DATEDIFF(MINUTE, GETUTCDATE(), GETDATE()), STATS_DATE({0}, {1}))
      , DataCompression  = @Compression
+     , StatsSampled     = NULL
+     , RowsSampled      = NULL
+FROM sys.dm_db_index_physical_stats(@DBID, {0}, {1}, {2}, '{3}')
+WHERE [index_level] = 0
+    AND [alloc_unit_type_desc] = 'IN_ROW_DATA'
+";
+
+    public const string AfterFixIndexWithStats = @"
+DECLARE @UnusedPagesCount  BIGINT
+      , @ReservedPageCount BIGINT
+      , @RowsCount         BIGINT
+      , @Compression       TINYINT
+      , @DBID              INT
+      , @DBNAME            SYSNAME
+      , @StatsSampled      FLOAT
+      , @RowsSampled       BIGINT
+
+SET @DBNAME = DB_NAME()
+SELECT @DBID = [database_id]
+FROM sys.databases WITH(NOLOCK)
+WHERE [name] = @DBNAME
+
+SELECT TOP(1) @UnusedPagesCount   = [used_page_count]
+            , @ReservedPageCount  = [reserved_page_count]
+            , @RowsCount          = [row_count]
+FROM sys.dm_db_partition_stats WITH(NOLOCK)
+WHERE [object_id] = {0}
+    AND [index_id] = {1}
+    AND [partition_number] = {2}
+
+SELECT @Compression = [data_compression]
+FROM sys.partitions WITH(NOLOCK)
+WHERE [object_id] = {0}
+    AND [index_id] = {1}
+    AND [partition_number] = {2}
+
+SELECT TOP(1) @StatsSampled = [rows_sampled] * 100. / NULLIF([rows], 0)
+            , @RowsSampled  = [rows_sampled]
+FROM sys.dm_db_stats_properties({0}, {1})
+
+SELECT Fragmentation    = [avg_fragmentation_in_percent]
+     , PageSpaceUsed    = [avg_page_space_used_in_percent]
+     , PagesCount       = ISNULL(@ReservedPageCount, 0)
+     , UnusedPagesCount = ISNULL(CASE WHEN ABS(@ReservedPageCount - @UnusedPagesCount) > 32 THEN @ReservedPageCount - @UnusedPagesCount END, 0)
+     , RowsCount        = ISNULL(@RowsCount, 0)
+     , IndexStats       = DATEADD(MINUTE, -DATEDIFF(MINUTE, GETUTCDATE(), GETDATE()), STATS_DATE({0}, {1}))
+     , DataCompression  = @Compression
+     , StatsSampled     = @StatsSampled
+     , RowsSampled      = @RowsSampled
 FROM sys.dm_db_index_physical_stats(@DBID, {0}, {1}, {2}, '{3}')
 WHERE [index_level] = 0
     AND [alloc_unit_type_desc] = 'IN_ROW_DATA'
@@ -746,6 +795,8 @@ FROM sys.fn_column_store_row_groups({0})
      , RowsCount        = ISNULL([rows], 0)
      , IndexStats       = NULL
      , DataCompression  = [data_compression]
+     , StatsSampled     = NULL
+     , RowsSampled      = NULL
 FROM sys.partitions WITH(NOLOCK)
 WHERE [object_id] = {0}
     AND [index_id] = {1}

Server/QueryEngine.cs

@@ -358,20 +358,23 @@ public static void GetColumnstoreFragmentation(SqlConnection connection, Index i
 
     public static string FixIndex(SqlConnection connection, Index ix) {
       int indexId = ix.FixType == IndexOp.CREATE_COLUMNSTORE_INDEX && ix.IndexType == IndexType.HEAP ? 1 : ix.IndexId;
-
-      string sqlInfo = string.Format(ix.IsColumnstore ? Query.AfterFixColumnstoreIndex : Query.AfterFixIndex,
-                                     ix.ObjectId, indexId, ix.PartitionNumber, Settings.Options.ScanMode);
-
+      string sql;
       string query = ix.GetQuery();
-      string sql = ix.FixType == IndexOp.DISABLE_INDEX
-                || ix.FixType == IndexOp.DROP_INDEX
-                || ix.FixType == IndexOp.DROP_TABLE
-                || ix.FixType == IndexOp.CREATE_INDEX
-                || ix.FixType == IndexOp.UPDATE_STATISTICS_FULL
-                || ix.FixType == IndexOp.UPDATE_STATISTICS_RESAMPLE
-                || ix.FixType == IndexOp.UPDATE_STATISTICS_SAMPLE
-                      ? query
-                      : $"{query} \n {sqlInfo}";
+
+      if (ix.FixType == IndexOp.DISABLE_INDEX || ix.FixType == IndexOp.DROP_INDEX || ix.FixType == IndexOp.DROP_TABLE || ix.FixType == IndexOp.CREATE_INDEX) {
+        sql = query;
+      }
+      else {
+        string sqlInfo;
+        if (ix.IsColumnstore)
+          sqlInfo = Query.AfterFixColumnstoreIndex;
+        else if (Settings.ServerInfo.IsFullStats && (ix.IndexType == IndexType.CLUSTERED || ix.IndexType == IndexType.NONCLUSTERED) && !ix.IsPartitioned)
+          sqlInfo = Query.AfterFixIndexWithStats;
+        else
+          sqlInfo = Query.AfterFixIndex;
+
+        sql = $"{query} \n {string.Format(sqlInfo, ix.ObjectId, indexId, ix.PartitionNumber, Settings.Options.ScanMode)}";
+      }
 
       SqlCommand cmd = new SqlCommand(sql, connection) { CommandTimeout = Settings.Options.CommandTimeout };
       SqlDataAdapter adapter = new SqlDataAdapter(cmd);
@@ -386,10 +389,7 @@ public static string FixIndex(SqlConnection connection, Index ix) {
 
       if (string.IsNullOrEmpty(ix.Error)) {
         try {
-          if (ix.FixType == IndexOp.UPDATE_STATISTICS_FULL || ix.FixType == IndexOp.UPDATE_STATISTICS_RESAMPLE || ix.FixType == IndexOp.UPDATE_STATISTICS_SAMPLE) {
-            ix.IndexStats = DateTime.UtcNow;
-          }
-          else if (ix.FixType == IndexOp.CREATE_INDEX) {
+          if (ix.FixType == IndexOp.CREATE_INDEX) {
             ix.IndexStats = DateTime.UtcNow;
             ix.Fragmentation = 0;
           }
@@ -411,6 +411,8 @@ public static string FixIndex(SqlConnection connection, Index ix) {
             ix.RowsCount = row.Field<long>(Resources.RowsCount);
             ix.DataCompression = ((DataCompression)row.Field<byte>(Resources.DataCompression));
             ix.IndexStats = row.Field<DateTime?>(Resources.IndexStats);
+            ix.StatsSampled = row.Field<double?>(Resources.StatsSampled) ?? ix.StatsSampled;
+            ix.RowsSampled = row.Field<long?>(Resources.RowsSampled) ?? ix.RowsSampled;
 
             if (ix.FixType == IndexOp.CREATE_COLUMNSTORE_INDEX) {
               ix.IndexName = "CCL";