Delete

java.lang.Object
- simpledb.Operator
- - simpledb.Delete

All Implemented Interfaces:

java.io.Serializable, DbIterator
```
public class Delete
extends Operator
```
The delete operator. Delete reads tuples from its child operator and removes them from the table they belong to.

See Also:

Serialized Form

Field Summary

Fields
Modifier and Type Field and Description

private boolean calledOnce

private DbIterator iterator

private static long serialVersionUID

private TransactionId tid

Fields
Modifier and Type	Field and Description
`private boolean`	`calledOnce`
`private DbIterator`	`iterator`
`private static long`	`serialVersionUID`
`private TransactionId`	`tid`

Constructor Summary

Constructors
Constructor and Description
`Delete(TransactionId t, DbIterator child)` Constructor specifying the transaction that this delete belongs to as well as the child to read from.

Method Summary

All Methods Instance Methods Concrete Methods
Modifier and Type	Method and Description
`void`	`close()` Closes this iterator.
`protected Tuple`	`fetchNext()` Deletes tuples as they are read from the child operator.
`DbIterator[]`	`getChildren()`
`TupleDesc`	`getTupleDesc()` Returns the TupleDesc associated with this DbIterator.
`void`	`open()` Opens the iterator.
`void`	`rewind()` Resets the iterator to the start.
`void`	`setChildren(DbIterator[] children)` Set the children(child) of this operator.

Methods inherited from class simpledb.Operator
getEstimatedCardinality, hasNext, next, setEstimatedCardinality

Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

- Field Detail
  - serialVersionUID
```
private static final long serialVersionUID
```
    See Also:
    
    Constant Field Values
  - tid
```
private TransactionId tid
```
  - iterator
```
private DbIterator iterator
```
  - calledOnce
```
private boolean calledOnce
```
- Constructor Detail
  - Delete
```
public Delete(TransactionId t,
              DbIterator child)
```
    Constructor specifying the transaction that this delete belongs to as well as the child to read from.
    
    Parameters:
    
    t - The transaction this delete runs in
    
    child - The child operator from which to read tuples for deletion
- Method Detail
  - getTupleDesc
```
public TupleDesc getTupleDesc()
```
    Description copied from interface: DbIterator
    
    Returns the TupleDesc associated with this DbIterator.
    
    Specified by:
    
    getTupleDesc in interface DbIterator
    
    Specified by:
    
    getTupleDesc in class Operator
    
    Returns:
    
    return the TupleDesc of the output tuples of this operator
  - open
```
public void open()
          throws DbException,
                 TransactionAbortedException
```
    Description copied from interface: DbIterator
    
    Opens the iterator. This must be called before any of the other methods.
    
    Specified by:
    
    open in interface DbIterator
    
    Overrides:
    
    open in class Operator
    
    Throws:
    
    DbException - when there are problems opening/accessing the database.
    
    TransactionAbortedException
  - close
```
public void close()
```
    Description copied from class: Operator
    
    Closes this iterator. If overridden by a subclass, they should call super.close() in order for Operator's internal state to be consistent.
    
    Specified by:
    
    close in interface DbIterator
    
    Overrides:
    
    close in class Operator
  - rewind
```
public void rewind()
            throws DbException,
                   TransactionAbortedException
```
    Description copied from interface: DbIterator
    
    Resets the iterator to the start.
    
    Throws:
    
    DbException - when rewind is unsupported.
    
    TransactionAbortedException
  - fetchNext
```
protected Tuple fetchNext()
                   throws TransactionAbortedException,
                          DbException
```
    Deletes tuples as they are read from the child operator. Deletes are processed via the buffer pool (which can be accessed via the Database.getBufferPool() method.
    
    Specified by:
    
    fetchNext in class Operator
    
    Returns:
    
    A 1-field tuple containing the number of deleted records.
    
    Throws:
    
    TransactionAbortedException
    
    DbException
    
    See Also:
    
    Database.getBufferPool(), BufferPool.deleteTuple(simpledb.TransactionId, simpledb.Tuple)
  - getChildren
```
public DbIterator[] getChildren()
```
    Specified by:
    
    getChildren in class Operator
    
    Returns:
    
    return the children DbIterators of this operator. If there is only one child, return an array of only one element. For join operators, the order of the children is not important. But they should be consistent among multiple calls.
  - setChildren
```
public void setChildren(DbIterator[] children)
```
    Description copied from class: Operator
    
    Set the children(child) of this operator. If the operator has only one child, children[0] should be used. If the operator is a join, children[0] and children[1] should be used.
    
    Specified by:
    
    setChildren in class Operator
    
    Parameters:
    
    children - the DbIterators which are to be set as the children(child) of this operator

Class Delete

Field Summary

Constructor Summary

Method Summary

Methods inherited from class simpledb.Operator

Methods inherited from class java.lang.Object

Field Detail

serialVersionUID

tid

iterator

calledOnce

Constructor Detail

Delete

Method Detail

getTupleDesc

open

close

rewind

fetchNext

getChildren

setChildren