com.mapr.ojai.store.impl

Class EligibleIndex

java.lang.Object

com.mapr.ojai.store.impl.EligibleIndex

public class EligibleIndex
extends java.lang.Object

Describes an eligible index; such an index can be used for a query, subject to the properties set herein. Index eligibility does not include the cost of scanning; that must be determined based on the actual scan ranges for each execution of the query. Index eligibility does not change across executions of the same query.

Field Summary

Fields

Modifier and Type	Field and Description
boolean	canBeUsedForSort Indicates that the index can be used for a requested sort.
boolean	conditionCovered Indicates that original query condition is covered by this index; the prunedCondition is the same as the original query condition.
static java.util.Comparator<EligibleIndex>	COST_COMPARATOR Comparator that can be used to compare EligibleIndexes by cost.
double	cpuCost
com.mapr.db.index.IndexDesc	indexDesc The index descriptor for the index.
com.mapr.db.scan.ScanStats	indexStats The scan stats for this index for the prunedCondition.
double	ioCost
boolean	isCovering Whether or not the index is covering.
int	nIncludedFields
int	nIndexedFields
org.ojai.store.QueryCondition	prunedCondition The condition that results if all of the conditions on fields that are not present in the index are removed.
double	rowSelectivity Approximate selectivity.
int	scanFields The fields of the index that are to be scanned.
double	simpleCost We estimate a simple cost to using this index.
double	sortCpuCost
java.util.List<org.ojai.FieldPath>	sortLimitExtras Immutable list of fields that are required for a client-side sort that are not included in the projection.

Constructor Summary

Constructors

Constructor and Description
EligibleIndex(com.mapr.db.index.IndexDesc indexDesc, int scanFields, boolean isCovering, boolean needsSort, boolean canBeUsedForSort, java.util.List<org.ojai.FieldPath> sortLimitExtras, OjaiConnection ojaiConnection, OjaiQuery ojaiQuery, com.mapr.db.scan.ScanStats tableStats, SharedTable sharedPrimaryTable) Constructor.

Method Summary

Modifier and Type	Method and Description
java.lang.String	toString()

Methods inherited from class java.lang.Object

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

Field Detail

indexDesc

public final com.mapr.db.index.IndexDesc indexDesc

The index descriptor for the index.

scanFields

public final int scanFields

The fields of the index that are to be scanned. The count indicates how many leading fields are to be included in the scan.

isCovering

public final boolean isCovering

Whether or not the index is covering.

canBeUsedForSort

public final boolean canBeUsedForSort

Indicates that the index can be used for a requested sort.

sortLimitExtras

public final java.util.List<org.ojai.FieldPath> sortLimitExtras

Immutable list of fields that are required for a client-side sort that are not included in the projection. Used to augment the select list and to know what fields to remove after the client-side sort.

prunedCondition

public final org.ojai.store.QueryCondition prunedCondition

The condition that results if all of the conditions on fields that are not present in the index are removed. If this index is selected, this can be used to perform the index scan.

conditionCovered

public final boolean conditionCovered

Indicates that original query condition is covered by this index; the prunedCondition is the same as the original query condition.

indexStats

public final com.mapr.db.scan.ScanStats indexStats

The scan stats for this index for the prunedCondition.

rowSelectivity

public final double rowSelectivity

Approximate selectivity. This is computed by comparing the estimated number of rows in the table with the estimated number of rows in the scan ranges (via ScanStats) for the index.

ioCost

public final double ioCost

cpuCost

public final double cpuCost

sortCpuCost

public final double sortCpuCost

simpleCost

public final double simpleCost

We estimate a simple cost to using this index. This is used to determine which index is best to use.

nIndexedFields

public final int nIndexedFields

nIncludedFields

public final int nIncludedFields

COST_COMPARATOR

public static final java.util.Comparator<EligibleIndex> COST_COMPARATOR

Comparator that can be used to compare EligibleIndexes by cost.

Constructor Detail

EligibleIndex

public EligibleIndex(com.mapr.db.index.IndexDesc indexDesc,
                     int scanFields,
                     boolean isCovering,
                     boolean needsSort,
                     boolean canBeUsedForSort,
                     java.util.List<org.ojai.FieldPath> sortLimitExtras,
                     OjaiConnection ojaiConnection,
                     OjaiQuery ojaiQuery,
                     com.mapr.db.scan.ScanStats tableStats,
                     SharedTable sharedPrimaryTable)
              throws java.io.IOException

Constructor.

Parameters:

indexDesc - the index descriptor

scanFields - how many of the index fields are used for the condition and/or sort

isCovering - the index covers the query

needsSort - the query requires a sort

canBeUsedForSort - this index can be used for the sort

sortLimitExtras - the list of additional fields a sort-limit needs for a client-side sort

ojaiConnection - the ojai connection

ojaiQuery - the query

tableStats - the table stats for the primary table

sharedPrimaryTable - the shared reference to the index this is for

Throws:

java.io.IOException

Method Detail

toString

public java.lang.String toString()

Overrides:

toString in class java.lang.Object