internal CompressedRecordPage GetCompressedRecordPage(PagePointer loc, CompressionContext compression)
{
if (compression.CompressionLevel == CompressionLevel.None)
{
throw new ArgumentException("Can't load compressed page with a compression level of none.");
}
Debug.WriteLine("Loading compressed record page " + loc);
return(new CompressedRecordPage(GetPageBytes(loc), compression, this));
}
/// <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;
}
}
internal PrimaryRecordPage GetPrimaryRecordPage(PagePointer loc, CompressionContext compression, bool isSysTable = true)
{
Debug.WriteLine("Loading Primary Record Page " + loc);
return(new PrimaryRecordPage(GetPageBytes(loc, isSysTable), compression, this));
}
private IEnumerable <Row> ScanPartition(long partitionID, int partitionNumber, Row schema, bool isSysTable = true)
{
// Lookup partition
var partition = Database.Dmvs.Partitions
.SingleOrDefault(p => p.PartitionID == partitionID && p.PartitionNumber == partitionNumber);
if (partition == null)
{
throw new ArgumentException("Partition (" + partitionID + "." + partitionNumber + " does not exist.");
}
// Get allocation unit for in-row data
var au = Database.Dmvs.SystemInternalsAllocationUnits
.SingleOrDefault(x => x.ContainerID == partition.PartitionID && x.Type == 1);
if (au == null)
{
throw new ArgumentException("Partition (" + partition.PartitionID + "." + partition.PartitionNumber + " has no HOBT allocation unit.");
}
// Before we can scan either heaps or indices, we need to know the compression level as that's set at the partition level, and not at the record/page level.
// We also need to know whether the partition is using vardecimals.
var compression = new CompressionContext((CompressionLevel)partition.DataCompression, MetaData.PartitionHasVardecimalColumns(partition.PartitionID));
var clusteredIndex = isSysTable ? null : Database.Dmvs.Indexes.SingleOrDefault(x => x.ObjectID == partition.ObjectID && x.Type == 1);
var useClusteredIndex = isSysTable || clusteredIndex != null;
var partitionColumns = isSysTable ? null : Database.Dmvs.SystemInternalsPartitionColumns.Where(x => x.PartitionID == partition.PartitionID).ToArray();
var defaultConstraints = isSysTable ? null : Database.Dmvs.SysDefaultConstraints.Where(x => x.ParentObjectId == partition.ObjectID).ToArray();
var schemaWrapper = new DataExtractorHelper(schema, Database.Dmvs, null, partitionColumns, defaultConstraints);
// Heap tables won't have root pages, thus we can check whether a root page is defined for the HOBT allocation unit
if (au.RootPagePointer != PagePointer.Zero && useClusteredIndex)
{
var currentPage = isSysTable ? au.FirstPagePointer : au.RootPagePointer;
if (currentPage != au.FirstPagePointer)
{
while (true)
{
var ciPage = Database.GetClusteredIndexPage(currentPage, isSysTable);
currentPage = ciPage.Records.Select(x => x.PageId).FirstOrDefault();
if (ciPage.Header.Level <= 1)
{
break;
}
}
}
// Index
foreach (var row in ScanLinkedDataPages(currentPage, schemaWrapper, compression, isSysTable))
{
yield return(row);
}
}
else
{
// Heap
foreach (var row in ScanHeap(au.FirstIamPagePointer, schemaWrapper, compression, isSysTable))
{
yield return(row);
}
}
}
/// <summary>
/// Scans a linked list of pages returning an IEnumerable of typed rows with data & schema
/// </summary>
internal IEnumerable <TDataRow> ScanLinkedDataPages <TDataRow>(PagePointer loc, CompressionContext compression) where TDataRow : Row, new()
{
return(ScanLinkedDataPages(loc, new DataExtractorHelper(new TDataRow()), compression, true).Cast <TDataRow>());
}
/// <summary>
/// Scans a heap beginning from the provided IAM page and onwards.
/// </summary>
private IEnumerable <Row> ScanHeap(PagePointer loc, DataExtractorHelper schema, CompressionContext compression,
bool isSysTable)
{
// Traverse the linked list of IAM pages until 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, isSysTable);
// 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, isSysTable);
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, isSysTable);
foreach (var dr in recordParser.GetEntities(schema))
{
yield return(dr);
}
}
}
// Update current IAM chain location to the tail pointer
loc = iamPage.Header.NextPage;
}
}
/// <summary>
/// Starts at the data page (loc) and follows the NextPage pointer chain till the end.
/// </summary>
internal IEnumerable <Row> ScanLinkedNonclusteredIndexPages(PagePointer loc, Row schema, CompressionContext compression)
{
while (loc != PagePointer.Zero)
{
var page = Database.GetNonclusteredIndexPage(loc);
foreach (var dr in page.GetEntities(schema, compression))
{
yield return(dr);
}
loc = page.Header.NextPage;
}
}
