org.apache.derby.iapi.store.access
Interface ScanInfo

All Known Implementing Classes:
BTreeScanInfo, HeapScanInfo, MergeScan, MergeScanRowSource, Scan, SortBufferRowSource, SortBufferScan, SortScan

public interface 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().

See Also:
GenericScanController.getScanInfo()

Method Summary
 java.util.Properties getAllScanInfo(java.util.Properties prop)
          Return all information gathered about the scan.
 

Method Detail

getAllScanInfo

java.util.Properties getAllScanInfo(java.util.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. These names have been internationalized, the names shown here are the old, non-internationalized names: scanType - type of the scan being performed: btree heap sort numPagesVisited - the number of pages visited during the scan. For btree scans this number only includes the leaf pages visited. numDeletedRowsVisited - the number of deleted rows visited during the scan. This number includes only those rows marked deleted. 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 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. columnsFetchedBitSet - The BitSet.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.

Parameters:
prop - Property list to fill in.
Throws:
StandardException - Standard exception policy.

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