IndexScan Class Reference

Performs condition-based scans over the entries of an index. More...

#include <IndexScan.h>

List of all members.

Public Member Functions
ReturnCode	openScan (IndexHandle *indexHandle, ComparisonOp compOp, const TypedValue *value)
	Opens an index scan.
ReturnCode	getNextEntry (RecordID *rid)
	Gets the next record matching the selection condition.
ReturnCode	closeScan ()
	Closes the index scan.

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Detailed Description

Performs condition-based scans over the entries of an index.

The IndexScan class is used to perform condition-based scans over the entries of a B+ tree index.

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Member Function Documentation

ReturnCode IndexScan::openScan	(	IndexHandle *	indexHandle,
		ComparisonOp	compOp,
		const TypedValue *	value
	)

Opens an index scan.

Parameters:

	indexHandle	The handle for the index to be scanned
	compOp	The comparison operator to be used for the scan
	value	The typed value to be compared against for the scan

Opens a condition-based scan over the entries in the open index referred to by parameter indexHandle. Once underway, the scan should produce the record ids of all records whose indexed attribute value compares in the specified way with the specified value. Parameters compOp and value are much as in RecordFileScan::openScan (including the possibility that compOp is ComparisonOp::NO_OP and value is a null pointer, indicating a complete scan). The only exception is that for B+ tree scans, you may choose to disallow comparison operator ComparisonOp::NE_OP (not equal). You will need to use the proper field of the value union type for the attribute, as in RecordFileScan. Also, as in IndexHandle::insertEntry, if the indexed attribute is a character string of length n, then you may assume that value is exactly n bytes long (and might not be null-terminated). Returns RC_OK on success, and non-zero RC codes on failure. An open scan should eventually be closed by the client by a call to IndexScan::closeScan.

ReturnCode IndexScan::getNextEntry

(

RecordID *

rid

)

Gets the next record matching the selection condition.

Parameters:

rid

Out parameter for the id of the next matching record

Gets the next record in the index matching the selection condition for the scan, returning its identifier in the rid out parameter. Returns RC_OK on success, RC_EOF if there are no more matching records, and other RC codes otherwise. You may assume that IndexManager clients will not close the corresponding open index while a scan is underway.

ReturnCode IndexScan::closeScan

(

)

Closes the index scan.

Terminates the index scan, freeing whatever resources are associated with the scan. Returns RC_OK on succcess, and other RC codes otherwise.

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The documentation for this class was generated from the following files:

• IndexScan.h
• IndexScan.cpp