org.vanilladb.core.query.algebra

Class AbstractJoinPlan

java.lang.Object

org.vanilladb.core.query.algebra.ReduceRecordsPlan

org.vanilladb.core.query.algebra.AbstractJoinPlan

All Implemented Interfaces:

Plan

Direct Known Subclasses:

HashJoinPlan, IndexJoinPlan, MergeJoinPlan

public abstract class AbstractJoinPlan
extends ReduceRecordsPlan

An abstract Plan class corresponding to the join relational algebra operator.

Constructor Summary

Constructors

Constructor and Description
AbstractJoinPlan()

Method Summary

Modifier and Type	Method and Description
static Histogram	joinHistogram(Histogram hist1, Histogram hist2, String fldName1, String fldName2) Returns a histogram that, for each field, approximates the value distribution of the join of the specified histograms.

Methods inherited from class org.vanilladb.core.query.algebra.ReduceRecordsPlan

syncHistogram

Methods inherited from class java.lang.Object

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

Methods inherited from interface org.vanilladb.core.query.algebra.Plan

blocksAccessed, histogram, open, recordsOutput, schema

Constructor Detail

AbstractJoinPlan

public AbstractJoinPlan()

Method Detail

joinHistogram

public static Histogram joinHistogram(Histogram hist1,
                                      Histogram hist2,
                                      String fldName1,
                                      String fldName2)

Returns a histogram that, for each field, approximates the value distribution of the join of the specified histograms.

Assumes that:

• Values in a bucket have the same frequency (uniform frequency)
• Given values within two equal ranges (of two joinable fields), all values in the range having smaller number of values appear in the range having larger number of values
• Distributions of values in different fields are independent with each other

Parameters:

hist1 - the left-hand histogram

hist2 - the right-hand histogram

fldName1 - the left-hand join field

fldName2 - the right-hand join field

Returns:

a histogram that, for each field, approximates the value distribution of the join