org.vanilladb.core.query.algebra

Interface Scan

All Superinterfaces:

Record

All Known Subinterfaces:

UpdateScan

All Known Implementing Classes:

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

public interface Scan
extends Record

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

The beforeFirst() method must be called before next().

Method Summary

Modifier and Type	Method and Description
void	beforeFirst() Positions the scan before its first record.
void	close() Closes the scan and its subscans, if any.
boolean	hasField(String fldName) Returns true if the scan has the specified field.
boolean	next() Moves the scan to the next record.

Methods inherited from interface org.vanilladb.core.sql.Record

getVal

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.

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