simpledb.query
Interface Scan

All Known Subinterfaces:

UpdateScan

All Known Implementing Classes:

ChunkScan, GroupByScan, IndexJoinScan, IndexSelectScan, MergeJoinScan, MultiBufferProductScan, ProductScan, ProjectScan, SelectScan, SortScan, TableScan

public interface Scan

The interface will be implemented by each query scan. There is a Scan class for each relational algebra operator.

Author:

Edward Sciore

Method Summary

void	beforeFirst() Positions the scan before its first record.
void	close() Closes the scan and its subscans, if any.
int	getInt(String fldname) Returns the value of the specified integer field in the current record.
String	getString(String fldname) Returns the value of the specified string field in the current record.
Constant	getVal(String fldname) Returns the value of the specified field in the current record.
boolean	hasField(String fldname) Returns true if the scan has the specified field.
boolean	next() Moves the scan to the next record.

Method Detail

beforeFirst

void beforeFirst()

Positions the scan before its first record.

next

boolean next()

Moves the scan to the next record.

Returns:

false if there is no next record

close

void close()

Closes the scan and its subscans, if any.

getVal

Constant getVal(String fldname)

Returns the value of the specified field in the current record. The value is expressed as a Constant.

Parameters:

fldname - the name of the field

Returns:

the value of that field, expressed as a Constant.

getInt

int getInt(String fldname)

Returns the value of the specified integer field in the current record.

Parameters:

fldname - the name of the field

Returns:

the field's integer value in the current record

getString

String getString(String fldname)

Returns the value of the specified string field in the current record.

Parameters:

fldname - the name of the field

Returns:

the field's string value in the current record

hasField

boolean hasField(String fldname)

Returns true if the scan has the specified field.

Parameters:

fldname - the name of the field

Returns:

true if the scan has that field