/// <summary> /// Starts at the data page (loc) and follows the NextPage pointer chain till the end. /// </summary> internal IEnumerable <Row> ScanLinkedDataPages(PagePointer loc, Row schema, CompressionContext compression) { while (loc != PagePointer.Zero) { var recordParser = RecordEntityParser.CreateEntityParserForPage(loc, compression, Database); foreach (var dr in recordParser.GetEntities(schema)) { yield return(dr); } loc = recordParser.NextPage; } }
/// <summary> /// Starts at the data page (loc) and follows the NextPage pointer chain till the end. /// </summary> internal IEnumerable <Row> ScanLinkedDataPages(PagePointer loc, DataExtractorHelper schema, CompressionContext compression, bool isSysTable) { while (PagePointer.Zero != loc && loc != null && loc.PageID > 0) { var recordParser = RecordEntityParser.CreateEntityParserForPage(loc, compression, Database, isSysTable); foreach (var dr in recordParser.GetEntities(schema)) { yield return(dr); } loc = recordParser.NextPage; } }
/// <summary> /// Scans a heap beginning from the provided IAM page and onwards. /// </summary> private IEnumerable <Row> scanHeap(PagePointer loc, Row schema, CompressionContext compression) { // Traverse the linked list of IAM pages untill the tail pointer is zero while (loc != PagePointer.Zero) { // Before scanning, check that the IAM page itself is allocated var pfsPage = Database.GetPfsPage(PfsPage.GetPfsPointerForPage(loc)); // If IAM page isn't allocated, there's nothing to return if (!pfsPage.GetPageDescription(loc.PageID).IsAllocated) { yield break; } var iamPage = Database.GetIamPage(loc); // Create an array with all of the header slot pointers var iamPageSlots = new[] { iamPage.Slot0, iamPage.Slot1, iamPage.Slot2, iamPage.Slot3, iamPage.Slot4, iamPage.Slot5, iamPage.Slot6, iamPage.Slot7 }; // Loop each header slot and yield the results, provided the header slot is allocated foreach (var slot in iamPageSlots.Where(x => x != PagePointer.Zero)) { var recordParser = RecordEntityParser.CreateEntityParserForPage(slot, compression, Database); foreach (var dr in recordParser.GetEntities(schema)) { yield return(dr); } } // Then loop through allocated extents and yield results foreach (var extent in iamPage.GetAllocatedExtents()) { // Get PFS page that tracks this extent var pfs = Database.GetPfsPage(PfsPage.GetPfsPointerForPage(extent.StartPage)); foreach (var pageLoc in extent.GetPagePointers()) { // Check if page is allocated according to PFS page var pfsDescription = pfs.GetPageDescription(pageLoc.PageID); if (!pfsDescription.IsAllocated) { continue; } var recordParser = RecordEntityParser.CreateEntityParserForPage(pageLoc, compression, Database); foreach (var dr in recordParser.GetEntities(schema)) { yield return(dr); } } } // Update current IAM chain location to the tail pointer loc = iamPage.Header.NextPage; } }