com.apple.foundationdb.record.query.plan

Class PlanOrderingKey

java.lang.Object

com.apple.foundationdb.record.query.plan.PlanOrderingKey

@API(value=INTERNAL)
public class PlanOrderingKey
extends Object

The keys that order the results from a plan. Given a record type with primary key k1, k2 and an index on k1, v1, v2, the index entries are k1, v1, v2, k2. Given a scan on this index for k1 = ? AND v1 = ?, the results are dictionary ordered by v2, k2. Up to prefixSize, 2 in this case, the ordering is trivial: all records have the same value. primaryKeyStart is the earlier position for part of the primary key; in this case, 0. primaryKeyTail is the position after which only primary key fields appear; in this case, 3.

Constructor Summary

Constructors

Constructor and Description
PlanOrderingKey(List<KeyExpression> keys, int prefixSize, int primaryKeyStart, int primaryKeyTail)

Method Summary

Modifier and Type	Method and Description
static PlanOrderingKey	forPlan(RecordMetaData metaData, RecordQueryPlan queryPlan, KeyExpression primaryKey)
List<KeyExpression>	getKeys()
int	getPrefixSize()
int	getPrimaryKeyStart()
int	getPrimaryKeyTail()
boolean	isPrimaryKeyOrdered() Return true if only primary key fields follow the prefix.
static KeyExpression	mergedComparisonKey(List<RecordQueryPlanner.ScoredPlan> plans, KeyExpression candidateKey, boolean candidateOnly) Get a key to be evaluated on record results to drive a merge.

Methods inherited from class java.lang.Object

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

Constructor Detail

PlanOrderingKey

public PlanOrderingKey(@Nonnull
                       List<KeyExpression> keys,
                       int prefixSize,
                       int primaryKeyStart,
                       int primaryKeyTail)

Method Detail

getKeys

@Nonnull
public List<KeyExpression> getKeys()

getPrefixSize

public int getPrefixSize()

getPrimaryKeyStart

public int getPrimaryKeyStart()

getPrimaryKeyTail

public int getPrimaryKeyTail()

isPrimaryKeyOrdered

public boolean isPrimaryKeyOrdered()

Return true if only primary key fields follow the prefix. If so, all the (non-trivial) ordering of results is by primary key.

Returns:

true if this ordering key is ordered by primary key

forPlan

@Nullable
public static PlanOrderingKey forPlan(@Nonnull
                                                RecordMetaData metaData,
                                                @Nonnull
                                                RecordQueryPlan queryPlan,
                                                @Nullable
                                                KeyExpression primaryKey)

mergedComparisonKey

@Nullable
public static KeyExpression mergedComparisonKey(@Nonnull
                                                          List<RecordQueryPlanner.ScoredPlan> plans,
                                                          @Nullable
                                                          KeyExpression candidateKey,
                                                          boolean candidateOnly)

Get a key to be evaluated on record results to drive a merge. This key must respect the underlying ordering so that only a single record needs to be buffered from each cursor. And it must uniquely identify duplicates by including the primary key.

Parameters:

plans - the plans for which to find a compatible ordering

candidateKey - a suggested key to use

candidateOnly - only accept the given candidate

Returns:

a comparison key compatible with all the plans