simpledb.materialize
Class SortPlan

java.lang.Object
  simpledb.materialize.SortPlan

All Implemented Interfaces:

Plan

public class SortPlan
extends Object
implements Plan

The Plan class for the sort operator.

Author:

Edward Sciore

Constructor Summary

SortPlan(Plan p, List<String> sortfields, Transaction tx)
Creates a sort plan for the specified query.

Method Summary

int	blocksAccessed() Returns the number of blocks in the sorted table, which is the same as it would be in a materialized table.
int	distinctValues(String fldname) Returns the number of distinct field values in the sorted table, which is the same as in the underlying query.
Scan	open() This method is where most of the action is.
int	recordsOutput() Returns the number of records in the sorted table, which is the same as in the underlying query.
Schema	schema() Returns the schema of the sorted table, which is the same as in the underlying query.

Methods inherited from class java.lang.Object

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

Constructor Detail

SortPlan

public SortPlan(Plan p,
                List<String> sortfields,
                Transaction tx)

Creates a sort plan for the specified query.

Parameters:

p - the plan for the underlying query

sortfields - the fields to sort by

tx - the calling transaction

Method Detail

open

public Scan open()

This method is where most of the action is. Up to 2 sorted temporary tables are created, and are passed into SortScan for final merging.

Specified by:

open in interface Plan

Returns:

a scan

See Also:

Plan.open()

blocksAccessed

public int blocksAccessed()

Returns the number of blocks in the sorted table, which is the same as it would be in a materialized table. It does not include the one-time cost of materializing and sorting the records.

Specified by:

blocksAccessed in interface Plan

Returns:

the estimated number of block accesses

See Also:

Plan.blocksAccessed()

recordsOutput

public int recordsOutput()

Returns the number of records in the sorted table, which is the same as in the underlying query.

Specified by:

recordsOutput in interface Plan

Returns:

the estimated number of output records

See Also:

Plan.recordsOutput()

distinctValues

public int distinctValues(String fldname)

Returns the number of distinct field values in the sorted table, which is the same as in the underlying query.

Specified by:

distinctValues in interface Plan

Parameters:

fldname - the name of a field

Returns:

the estimated number of distinct field values in the output

See Also:

Plan.distinctValues(java.lang.String)

schema

public Schema schema()

Returns the schema of the sorted table, which is the same as in the underlying query.

Specified by:

schema in interface Plan

Returns:

the query's schema

See Also:

Plan.schema()