simpledb.index.query
Class IndexJoinPlan

java.lang.Object
  simpledb.index.query.IndexJoinPlan

All Implemented Interfaces:

Plan

public class IndexJoinPlan
extends Object
implements Plan

The Plan class corresponding to the indexjoin relational algebra operator.

Author:

Edward Sciore

Constructor Summary

IndexJoinPlan(Plan p1, Plan p2, IndexInfo ii, String joinfield, Transaction tx)
Implements the join operator, using the specified LHS and RHS plans.

Method Summary

int	blocksAccessed() Estimates the number of block accesses to compute the join.
int	distinctValues(String fldname) Estimates the number of distinct values for the specified field.
Scan	open() Opens an indexjoin scan for this query
int	recordsOutput() Estimates the number of output records in the join.
Schema	schema() Returns the schema of the index join.

Methods inherited from class java.lang.Object

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

Constructor Detail

IndexJoinPlan

public IndexJoinPlan(Plan p1,
                     Plan p2,
                     IndexInfo ii,
                     String joinfield,
                     Transaction tx)

Implements the join operator, using the specified LHS and RHS plans.

Parameters:

p1 - the left-hand plan

p2 - the right-hand plan

ii - information about the right-hand index

joinfield - the left-hand field used for joining

tx - the calling transaction

Method Detail

open

public Scan open()

Opens an indexjoin scan for this query

Specified by:

open in interface Plan

Returns:

a scan

See Also:

Plan.open()

blocksAccessed

public int blocksAccessed()

Estimates the number of block accesses to compute the join. The formula is:

 B(indexjoin(p1,p2,idx)) = B(p1) + R(p1)*B(idx)
       + R(indexjoin(p1,p2,idx) 

Specified by:

blocksAccessed in interface Plan

Returns:

the estimated number of block accesses

See Also:

Plan.blocksAccessed()

recordsOutput

public int recordsOutput()

Estimates the number of output records in the join. The formula is:

 R(indexjoin(p1,p2,idx)) = R(p1)*R(idx) 

Specified by:

recordsOutput in interface Plan

Returns:

the estimated number of output records

See Also:

Plan.recordsOutput()

distinctValues

public int distinctValues(String fldname)

Estimates the number of distinct values for the specified field.

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 index join.

Specified by:

schema in interface Plan

Returns:

the query's schema

See Also:

Plan.schema()