simpledb.query
Class TableScan

java.lang.Object
  simpledb.query.TableScan

All Implemented Interfaces:

Scan, UpdateScan

public class TableScan
extends Object
implements UpdateScan

The Scan class corresponding to a table. A table scan is just a wrapper for a RecordFile object; most methods just delegate to the corresponding RecordFile methods.

Author:

Edward Sciore

Constructor Summary

TableScan(TableInfo ti, Transaction tx)
Creates a new table scan, and opens its corresponding record file.

Method Summary

void	beforeFirst() Positions the scan before its first record.
void	close() Closes the scan and its subscans, if any.
void	delete() Deletes the current record from the scan.
int	getInt(String fldname) Returns the value of the specified integer field in the current record.
RID	getRid() Returns the RID of 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, as a Constant.
boolean	hasField(String fldname) Returns true if the scan has the specified field.
void	insert() Inserts a new record somewhere in the scan.
void	moveToRid(RID rid) Positions the scan so that the current record has the specified RID.
boolean	next() Moves the scan to the next record.
void	setInt(String fldname, int val) Modifies the field value of the current record.
void	setString(String fldname, String val) Modifies the field value of the current record.
void	setVal(String fldname, Constant val) Sets the value of the specified field, as a Constant.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

TableScan

public TableScan(TableInfo ti,
                 Transaction tx)

Creates a new table scan, and opens its corresponding record file.

Parameters:

ti - the table's metadata

tx - the calling transaction

Method Detail

beforeFirst

public void beforeFirst()

Description copied from interface: Scan

Positions the scan before its first record.

Specified by:

beforeFirst in interface Scan

next

public boolean next()

Description copied from interface: Scan

Moves the scan to the next record.

Specified by:

next in interface Scan

Returns:

false if there is no next record

close

public void close()

Description copied from interface: Scan

Closes the scan and its subscans, if any.

Specified by:

close in interface Scan

getVal

public Constant getVal(String fldname)

Returns the value of the specified field, as a Constant. The schema is examined to determine the field's type. If INTEGER, then the record file's getInt method is called; otherwise, the getString method is called.

Specified by:

getVal in interface Scan

Parameters:

fldname - the name of the field

Returns:

the value of that field, expressed as a Constant.

See Also:

Scan.getVal(java.lang.String)

getInt

public int getInt(String fldname)

Description copied from interface: Scan

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

Specified by:

getInt in interface Scan

Parameters:

fldname - the name of the field

Returns:

the field's integer value in the current record

getString

public String getString(String fldname)

Description copied from interface: Scan

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

Specified by:

getString in interface Scan

Parameters:

fldname - the name of the field

Returns:

the field's string value in the current record

hasField

public boolean hasField(String fldname)

Description copied from interface: Scan

Returns true if the scan has the specified field.

Specified by:

hasField in interface Scan

Parameters:

fldname - the name of the field

Returns:

true if the scan has that field

setVal

public void setVal(String fldname,
                   Constant val)

Sets the value of the specified field, as a Constant. The schema is examined to determine the field's type. If INTEGER, then the record file's setInt method is called; otherwise, the setString method is called.

Specified by:

setVal in interface UpdateScan

Parameters:

fldname - the name of the field

val - the new value, expressed as a Constant

See Also:

UpdateScan.setVal(java.lang.String, simpledb.query.Constant)

setInt

public void setInt(String fldname,
                   int val)

Description copied from interface: UpdateScan

Modifies the field value of the current record.

Specified by:

setInt in interface UpdateScan

Parameters:

fldname - the name of the field

val - the new integer value

setString

public void setString(String fldname,
                      String val)

Description copied from interface: UpdateScan

Modifies the field value of the current record.

Specified by:

setString in interface UpdateScan

Parameters:

fldname - the name of the field

val - the new string value

delete

public void delete()

Description copied from interface: UpdateScan

Deletes the current record from the scan.

Specified by:

delete in interface UpdateScan

insert

public void insert()

Description copied from interface: UpdateScan

Inserts a new record somewhere in the scan.

Specified by:

insert in interface UpdateScan

getRid

public RID getRid()

Description copied from interface: UpdateScan

Returns the RID of the current record.

Specified by:

getRid in interface UpdateScan

Returns:

the RID of the current record

moveToRid

public void moveToRid(RID rid)

Description copied from interface: UpdateScan

Positions the scan so that the current record has the specified RID.

Specified by:

moveToRid in interface UpdateScan

Parameters:

rid - the RID of the desired record