Package com.apple.foundationdb.record.query.plan.temp.view

Class ViewExpression

java.lang.Object

com.apple.foundationdb.record.query.plan.temp.view.ViewExpression

public class ViewExpression
extends Object

An abstraction that represents a stream of values that can be represented as tuple-encoding keys and binary values in FoundationDB.

Visually, a view expression is quite similar to a query in a declarative language like SQL. A view expression is composed of several clauses, including:

• A root Source, which defines the stream of values from which the expression's Elements are generated.
• A projection, which is a collection of Elements that generate values.
• A sort order, which is an ordered list of Elements that define the order of the stream. By definition, the sort order is the lexicographic order of the elements when packed together as tuple.
• A predicate, in the form of a QueryPredicate

Because view expressions are quite general but are closely tied to the semantics of the tuple layer, they are very useful for planning tasks such as incremental index selection. To see how an index is represented as a view expression, see fromIndexDefinition(String, Collection, KeyExpression).

Nested Class Summary

Nested Classes

Modifier and Type	Class	Description
static class	ViewExpression.Builder	A builder class for constructing an (immutable) view expression.

Constructor Summary

Constructors

Constructor	Description
ViewExpression(List<Element> select, QueryPredicate predicate, Source rootSource, List<Element> orderBy)

Method Summary

Modifier and Type	Method	Description
static ViewExpression.Builder	builder()
static ViewExpression	fromIndexDefinition(String indexType, Collection<String> recordTypes, KeyExpression rootExpression)	Generate a view expression that represents the structure of an index defined using a KeyExpression.
List<Element>	getOrderBy()

Methods inherited from class java.lang.Object

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

Constructor Detail

ViewExpression

public ViewExpression(@Nonnull
                      List<Element> select,
                      @Nullable
                      QueryPredicate predicate,
                      @Nonnull
                      Source rootSource,
                      @Nonnull
                      List<Element> orderBy)

Method Detail

getOrderBy

@Nonnull
public List<Element> getOrderBy()

fromIndexDefinition

public static ViewExpression fromIndexDefinition(@Nonnull
                                                 String indexType,
                                                 @Nonnull
                                                 Collection<String> recordTypes,
                                                 @Nonnull
                                                 KeyExpression rootExpression)

Generate a view expression that represents the structure of an index defined using a KeyExpression.

Parameters:

indexType - the type of the index as specified in the meta-data

recordTypes - the set of record types used to generate the index

rootExpression - the root key expression of the index as specified in the meta-data

Returns:

a view expression representing the given index structure

builder

public static ViewExpression.Builder builder()