org.cloudgraph.hbase.expr

Class PathPredicateBinaryExprTreeAssembler

java.lang.Object

org.plasma.query.visitor.DefaultQueryVisitor

org.cloudgraph.query.expr.ExpresionVisitorSupport

org.cloudgraph.query.expr.DefaultBinaryExprTreeAssembler

org.cloudgraph.hbase.expr.PathPredicateBinaryExprTreeAssembler

All Implemented Interfaces:

ExprAssembler, org.plasma.query.visitor.QueryVisitor

Direct Known Subclasses:

LocalEdgeRecognizerSyntaxTreeAssembler

public abstract class PathPredicateBinaryExprTreeAssembler
extends DefaultBinaryExprTreeAssembler

A binary expression tree assembler which constructs an operator precedence map, then visits (traverses) the given predicate expression syntax tree depth-first using an adapted shunting-yard algorithm and assembles a resulting binary tree structure. In typical usage scenarios, a single expression tree is assembled once, and then used to evaluate any number of graph edge or other results based on a given context.

The adapted shunting-yard algorithm in general uses a stack of operators and operands, and as new binary tree nodes are detected and created they are pushed onto the operand stack based on operator precedence. The resulting binary expression tree reflects the syntax of the underlying query expression including the precedence of its operators.

The use of binary expression tree evaluation for post processing of graph edge results is necessary in columnar data stores, as an entity with multiple properties is necessarily persisted across multiple columns. And while these data stores provide many useful column oriented filters, the capability to select an entity based on complex criteria which spans several columns is generally not supported, as such filters are column oriented. Yet even for simple queries (e.g. "where entity.c1 = 'foo' and entity.c2 = 'bar'") column c1 and its value exists in one cell and column c2 exists in another table cell. Since columnar data store filters cannot generally span columns, both cells must be returned and the results post processed within the context of the binary expression tree.

Subclasses may provide alternate implementations of ExprAssembler which create binary expression tree nodes with specific evaluation behavior.

Since:

0.5.3

Author:

Scott Cinnamond

See Also:

Expr, CompositeColumnKeyFactory

Field Summary

Fields

Modifier and Type	Field and Description
protected CompositeColumnKeyFactory	columnKeyFactory
protected org.plasma.sdo.PlasmaType	edgeType

Fields inherited from class org.cloudgraph.query.expr.DefaultBinaryExprTreeAssembler

contextExpression, contextProperty, contextQueryProperty, contextType, predicates, rootType

Constructor Summary

Constructors

Constructor and Description
PathPredicateBinaryExprTreeAssembler(org.plasma.query.model.Where predicate, org.plasma.sdo.PlasmaType edgeType, org.plasma.sdo.PlasmaType rootType, StoreMappingContext mappingContext) Constructs an assembler based on the given predicate and graph edge type.

Method Summary

Modifier and Type	Method and Description
void	end(org.plasma.query.model.Property property) Process the traversal end event for a query property within an expression setting up context information for the endpoint property and its type, as well as physical column qualifier name bytes which are set into the DefaultBinaryExprTreeAssembler.contextQueryProperty physical name bytes.

Methods inherited from class org.cloudgraph.query.expr.DefaultBinaryExprTreeAssembler

createLogicalBinaryExpr, createPredicateBinaryExpr, createRelationalBinaryExpr, end, getResult, log, serialize, traverse

Methods inherited from class org.cloudgraph.query.expr.ExpresionVisitorSupport

getChildExpressionCount, getChildExpressions, getLogicalOperatorCount, hasChildExpressions, hasWildcard

Methods inherited from class org.plasma.query.visitor.DefaultQueryVisitor

end, end, end, end, end, end, end, end, end, end, end, end, end, end, end, end, end, end, end, end, end, end, end, getContext, start, start, start, start, start, start, start, start, start, start, start, start, start, start, start, start, start, start, start, start, start, start, start, start, start

Methods inherited from class java.lang.Object

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

Field Detail

columnKeyFactory

protected CompositeColumnKeyFactory columnKeyFactory

edgeType

protected org.plasma.sdo.PlasmaType edgeType

Constructor Detail

PathPredicateBinaryExprTreeAssembler

public PathPredicateBinaryExprTreeAssembler(org.plasma.query.model.Where predicate,
                                            org.plasma.sdo.PlasmaType edgeType,
                                            org.plasma.sdo.PlasmaType rootType,
                                            StoreMappingContext mappingContext)

Constructs an assembler based on the given predicate and graph edge type.

Parameters:

predicate - the predicate

edgeType - the graph edge type which is the type for the reference property within the graph which represents an edge

rootType - the graph root type

Method Detail

end

public void end(org.plasma.query.model.Property property)

Process the traversal end event for a query property within an expression setting up context information for the endpoint property and its type, as well as physical column qualifier name bytes which are set into the DefaultBinaryExprTreeAssembler.contextQueryProperty physical name bytes. for the current expression.

Specified by:

end in interface org.plasma.query.visitor.QueryVisitor

Overrides:

end in class DefaultBinaryExprTreeAssembler

See Also:

DefaultQueryVisitor.end(org.plasma.query.model.Property)