Package com.apple.foundationdb.record.query.plan.planning

Class BooleanNormalizer

java.lang.Object

com.apple.foundationdb.record.query.plan.planning.BooleanNormalizer

@API(INTERNAL)
public class BooleanNormalizer
extends Object

A normalizer of a tree of QueryComponent predicates into disjunctive normal form.

The full normal form has a single Or at the root, all of whose children are And, none of whose children have other Boolean operators. This is abbreviated to exclude parent Boolean nodes with only one child. The intermediate form for the normalizer is a list of lists.

The size of a Boolean expression in disjunctive normal form (DNF) is the number of terms in the outermost Or [O'Donnell 2014]. The BooleanNormalizer will not normalize a QueryComponent if the normalized form would have a size that exceeds the size limit. This limit is useful to avoid wastefully normalizing expressions with a very large DNF. In some cases, such as a large expression in conjunctive normal form (CNF), attempting to normalize such an expression will cause out-of-memory errors.

Field Summary

Fields

Modifier and Type	Field	Description
static int	DEFAULT_SIZE_LIMIT	The default limit on the size of the DNF that will be produced by the normalizer.

Method Summary

Modifier and Type	Method	Description
static BooleanNormalizer	getDefaultInstance()	Obtain a normalizer with the default size limit DEFAULT_SIZE_LIMIT.
QueryComponent	normalize(QueryComponent predicate)	Convert the given predicate to disjunctive normal form, if necessary.
QueryComponent	normalizeIfPossible(QueryComponent predicate)	Convert the given predicate to disjunctive normal form, if necessary.
static BooleanNormalizer	withLimit(int sizeLimit)	Obtain a normalizer with the given size limit.

Methods inherited from class java.lang.Object

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

Field Detail

DEFAULT_SIZE_LIMIT

public static final int DEFAULT_SIZE_LIMIT

The default limit on the size of the DNF that will be produced by the normalizer.

See Also:

Constant Field Values

Method Detail

getDefaultInstance

@Nonnull
public static BooleanNormalizer getDefaultInstance()

Obtain a normalizer with the default size limit DEFAULT_SIZE_LIMIT.

Returns:

a normalizer with the default size limit

withLimit

@Nonnull
public static BooleanNormalizer withLimit(int sizeLimit)

Obtain a normalizer with the given size limit.

Parameters:

sizeLimit - a limit on the size of DNF that this normalizer will produce

Returns:

a normalizer with the given size limit

normalizeIfPossible

@Nullable
public QueryComponent normalizeIfPossible(@Nullable
                                          QueryComponent predicate)

Convert the given predicate to disjunctive normal form, if necessary. If the size of the DNF would exceed the size limit, return the un-normalized predicate.

Parameters:

predicate - the query predicate to be normalized

Returns:

the predicate in disjunctive normal form if it does not exceed the size limit or the predicate otherwise

normalize

@Nullable
public QueryComponent normalize(@Nullable
                                QueryComponent predicate)

Convert the given predicate to disjunctive normal form, if necessary. If the size of the DNF would exceed the size limit, throw a BooleanNormalizer.DNFTooLargeException.

Parameters:

predicate - the query predicate to be normalized

Returns:

the predicate in disjunctive normal form

Throws:

com.apple.foundationdb.record.query.plan.planning.BooleanNormalizer.DNFTooLargeException - if the DNF would exceed the size limit