com.apple.foundationdb.record.query.plan

Class TextScan

java.lang.Object

com.apple.foundationdb.record.query.plan.TextScan

All Implemented Interfaces:

PlanHashable

@API(value=INTERNAL)
public class TextScan
extends Object
implements PlanHashable

Encapsulate the information necessary to scan a text-based index. In particular, this includes the work to translate the comparison type into the proper ranges of the index to scan and then combine.

NOTE: This API is still a work in progress and might change in a future without notice. This class should not be used outside of the Record Layer project.

Constructor Summary

Constructors

Constructor and Description
TextScan(Index index, ScanComparisons groupingComparisons, Comparisons.TextComparison textComparison, ScanComparisons suffixComparisons)

Method Summary

Modifier and Type	Method and Description
boolean	createsDuplicates() Determines whether this scan might return duplicate results for the same record.
boolean	equals(Object o)
ScanComparisons	getGroupingComparisons() Get any grouping comparisons necessary to scan only within one grouping key.
Index	getIndex() Get the index being scanned.
ScanComparisons	getSuffixComparisons() Get any comparisons performed on fields of the index following the text field.
Comparisons.TextComparison	getTextComparison() Get the comparison performed on the text field.
int	hashCode()
int	planHash() Return a hash similar to hashCode, but with the additional guarantee that is is stable across JVMs.
<M extends Message> RecordCursor<IndexEntry>	scan(FDBRecordStoreBase<M> store, EvaluationContext context, byte[] continuation, ScanProperties scanProperties) Scan the store to produce a cursor of index entries that all satisfy the comparison.
String	toString()

Methods inherited from class java.lang.Object

clone, finalize, getClass, notify, notifyAll, wait, wait, wait

Methods inherited from interface com.apple.foundationdb.record.PlanHashable

combineHashes, iterablePlanHash, objectPlanHash, objectsPlanHash, planHash, planHash, planHashUnordered, stringHashUnordered

Constructor Detail

TextScan

public TextScan(@Nonnull
                Index index,
                @Nullable
                ScanComparisons groupingComparisons,
                @Nonnull
                Comparisons.TextComparison textComparison,
                @Nullable
                ScanComparisons suffixComparisons)

Method Detail

scan

@Nonnull
public <M extends Message> RecordCursor<IndexEntry> scan(@Nonnull
                                                                  FDBRecordStoreBase<M> store,
                                                                  @Nonnull
                                                                  EvaluationContext context,
                                                                  @Nullable
                                                                  byte[] continuation,
                                                                  @Nonnull
                                                                  ScanProperties scanProperties)

Scan the store to produce a cursor of index entries that all satisfy the comparison.

Type Parameters:

M - message type associated with the store and evaluation context

Parameters:

store - the record store for the query

context - the query evaluation context

continuation - a continuation from a previous scan to resume query execution

scanProperties - execution properties of this scan

Returns:

a cursor of index entries from the given scan

createsDuplicates

public boolean createsDuplicates()

Determines whether this scan might return duplicate results for the same record. This can happen if this is a prefix scan (as the same prefix might correspond to multiple tokens in the same document) or if the index expression itself creates duplicates.

Returns:

true if this scan might return multiple entries for the same record

getIndex

@Nonnull
public Index getIndex()

Get the index being scanned.

Returns:

the index being scanned

getGroupingComparisons

@Nullable
public ScanComparisons getGroupingComparisons()

Get any grouping comparisons necessary to scan only within one grouping key. These comparisons should evaluate to "all of" a given tuple range. If the index does not have any grouping keys, this might return null or an empty ScanComparisons object.

Returns:

the scan comparisons necessary to scan over the value of one grouping key

getTextComparison

@Nonnull
public Comparisons.TextComparison getTextComparison()

Get the comparison performed on the text field. This will be some operation like checking the field for the presence of one or more tokens. This might end up producing multiple scans when run that are executed in parallel and combined.

Returns:

the comparison performed on the index's text field

getSuffixComparisons

@Nullable
public ScanComparisons getSuffixComparisons()

Get any comparisons performed on fields of the index following the text field. This could be done to satisfy additional predicates on those fields after the text predicate itself is satisfied. If there are no such comparisons, then this might return null or an empty ScanComparisons object.

Returns:

any scan comparisons performed after the text predicate is satisfied

toString

@Nonnull
public String toString()

Overrides:

toString in class Object

equals

public boolean equals(Object o)

Overrides:

equals in class Object

hashCode

public int hashCode()

Overrides:

hashCode in class Object

planHash

public int planHash()

Description copied from interface: PlanHashable

Return a hash similar to hashCode, but with the additional guarantee that is is stable across JVMs.

Specified by:

planHash in interface PlanHashable

Returns:

a stable hash code