simpledb.index.query
Class IndexSelectPlan

java.lang.Object
  simpledb.index.query.IndexSelectPlan

All Implemented Interfaces:

Plan

public class IndexSelectPlan
extends Object
implements Plan

The Plan class corresponding to the indexselect relational algebra operator.

Author:

Edward Sciore

Constructor Summary

IndexSelectPlan(Plan p, IndexInfo ii, Constant val, Transaction tx)
Creates a new indexselect node in the query tree for the specified index and selection constant.

Method Summary

int	blocksAccessed() Estimates the number of block accesses to compute the index selection, which is the same as the index traversal cost plus the number of matching data records.
int	distinctValues(String fldname) Returns the distinct values as defined by the index.
Scan	open() Creates a new indexselect scan for this query
int	recordsOutput() Estimates the number of output records in the index selection, which is the same as the number of search key values for the index.
Schema	schema() Returns the schema of the data table.

Methods inherited from class java.lang.Object

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

Constructor Detail

IndexSelectPlan

public IndexSelectPlan(Plan p,
                       IndexInfo ii,
                       Constant val,
                       Transaction tx)

Creates a new indexselect node in the query tree for the specified index and selection constant.

Parameters:

p - the input table

ii - information about the index

val - the selection constant

tx - the calling transaction

Method Detail

open

public Scan open()

Creates a new indexselect 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 index selection, which is the same as the index traversal cost plus the number of matching data records.

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 index selection, which is the same as the number of search key values for the index.

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 distinct values as defined by the index.

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 data table.

Specified by:

schema in interface Plan

Returns:

the query's schema

See Also:

Plan.schema()