Class BTreeScanInfo

java.lang.Object
org.apache.derby.impl.store.access.btree.BTreeScanInfo
All Implemented Interfaces:
ScanInfo

class BTreeScanInfo extends Object implements ScanInfo
This object provides performance information related to an open scan. The information is accumulated during operations on a ScanController() and then copied into this object and returned by a call to ScanController.getStatistic().
  • Field Details

    • stat_numpages_visited

      private int stat_numpages_visited
      Performance counters ...
    • stat_numrows_visited

      private int stat_numrows_visited
    • stat_numrows_qualified

      private int stat_numrows_qualified
    • stat_numdeleted_rows_visited

      private int stat_numdeleted_rows_visited
    • stat_numColumnsFetched

      private int stat_numColumnsFetched
    • stat_treeHeight

      private int stat_treeHeight
    • stat_validColumns

      private FormatableBitSet stat_validColumns
  • Constructor Details

    • BTreeScanInfo

      BTreeScanInfo(BTreeScan scan)
  • Method Details

    • getAllScanInfo

      public Properties getAllScanInfo(Properties prop) throws StandardException
      Return all information gathered about the scan.

      This routine returns a list of properties which contains all information gathered about the scan. If a Property is passed in, then that property list is appeneded to, otherwise a new property object is created and returned.

      Not all scans may support all properties, if the property is not supported then it will not be returned. The following is a list of properties that may be returned: numPagesVisited - the number of pages visited during the scan. For btree scans this number only includes the leaf pages visited. numRowsVisited - the number of rows visited during the scan. This number includes all rows, including: those marked deleted, those that don't meet qualification, ... numRowsQualified - the number of undeleted rows, which met the qualification. treeHeight (btree's only) - for btree's the height of the tree. A tree with one page has a height of 1. Total number of pages visited in a btree scan is (treeHeight - 1 + numPagesVisited). numColumnsFetched - the number of columns Fetched - partial scans will result in fetching less columns than the total number in the scan. columnsFetched - The FormatableBitSet.toString() method called on the validColumns arg. to the scan, unless validColumns was set to null, and in that case we will return "all". NOTE - this list will be expanded as more information about the scan is gathered and returned.

      Specified by:
      getAllScanInfo in interface ScanInfo
      Parameters:
      prop - Property list to fill in.
      Throws:
      StandardException - Standard exception policy.