Database Management Systems

by Raghu Ramakrishnan and Johannes Gehrke

Sample Iterator Trees

Tree A:

The call to get_next calls on the File Scan Iterator to retrieve tuples one at a time from the Heap File.

The details: The heap file is opened and a scan object is created. get_next is then called on the scan object.

FileScanIter::FileScanIter
- HeapFile::HeapFile
- HeapFile::openScan
FileScanIter::get_next
- Scan::get_next

Tree B:

The call to get_next calls on the Index Scan Iterator to retrieve tuples one at a time from the Heap File after the rid has been retrieved from the Access Method.

The details: The access method is opened and a scan object is created. get_next is then called on the scan object.

IndexScanIter::IndexScanIter
- BTreeFile::BTreeFile or LinearHashingFile::LinearHashingFile
- HeapFile::HeapFile
- BTreeFile::openScan or LinearHashingFile::openScan
IndexScanIter::get_next
- BTreeScan::get_next or LinearHashingScan::get_next
- HeapFile::getRecord

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