com.bigdata.bop.solutions

Interface IGroupByState

All Known Implementing Classes:

GroupByState

public interface IGroupByState

The state associated with a validated aggregation operator.

Version:

$Id$

Author:

Bryan Thompson

Method Summary

Methods

Modifier and Type	Method and Description
LinkedHashSet<IVariable<?>>	getColumnVars() Variables for which we will need column projections.
IValueExpression<?>[]	getGroupByClause() The ordered array of value expressions which define the basis for aggregating solutions into groups.
LinkedHashSet<IVariable<?>>	getGroupByVars() Top-level variables in the GROUP_BY clause in the order in which they were declared.
IConstraint[]	getHavingClause() Optional constraints applied to the aggregated solutions.
IValueExpression<?>[]	getSelectClause() The value expressions to be projected out of the SELECT clause.
LinkedHashSet<IVariable<?>>	getSelectVars() Top-level variables in the SELECT clause in the order in which they were declared.
boolean	isAnyDistinct() true iff any aggregate functions will be applied to the DISTINCT values arising from their inner value expression in either the SELECT or HAVING clause.
boolean	isNestedAggregates() true if any aggregate expression nests another aggregate expression.
boolean	isSelectDependency() true iff any aggregate expression uses a reference to another aggregate expression in the select clause.
boolean	isSimpleHaving() true if none of the value expressions in the optional HAVING clause use IAggregate functions.

Method Detail

getGroupByClause

IValueExpression<?>[] getGroupByClause()

The ordered array of value expressions which define the basis for aggregating solutions into groups.

getGroupByVars

LinkedHashSet<IVariable<?>> getGroupByVars()

Top-level variables in the GROUP_BY clause in the order in which they were declared. Computed value expressions which are not bound on a variable explicitly are NOT reported here.

getSelectClause

IValueExpression<?>[] getSelectClause()

The value expressions to be projected out of the SELECT clause.

getSelectVars

LinkedHashSet<IVariable<?>> getSelectVars()

Top-level variables in the SELECT clause in the order in which they were declared.

getHavingClause

IConstraint[] getHavingClause()

Optional constraints applied to the aggregated solutions.

getColumnVars

LinkedHashSet<IVariable<?>> getColumnVars()

Variables for which we will need column projections. For example, given SELECT SUM(DISTINCT ?x), SUM(?y), this would report {?x,?y}. The variables will be reported in the order they were encountered during a left-to-right scan of the SELECT expressions followed by a left-to-right scan of the HAVING constraints.

isAnyDistinct

boolean isAnyDistinct()

true iff any aggregate functions will be applied to the DISTINCT values arising from their inner value expression in either the SELECT or HAVING clause. When false certain optimizations are possible.

isSelectDependency

boolean isSelectDependency()

true iff any aggregate expression uses a reference to another aggregate expression in the select clause. When false certain optimizations are possible (parallel evaluation of the aggregates across the column projections).

isNestedAggregates

boolean isNestedAggregates()

true if any aggregate expression nests another aggregate expression. For example:

 SUM(?x+AVG(?x))
 

is a nested aggregation expression but:

 SUM(?x+1)
 

and

 1+SUM(?x)+AVG(?x)
 

are not nested aggregation expressions. When false certain optimizations may be possible.

isSimpleHaving

boolean isSimpleHaving()

true if none of the value expressions in the optional HAVING clause use IAggregate functions. When true certain optimizations are possible.

For example, the following query does not use an IAggregate function in the HAVING clause. Instead, it references an aggregate defined in the SELECT clause.

 SELECT SUM(?y) as ?x
 GROUP BY ?z
 HAVING ?x > 10
 

As a degenerate case, this is also true when there is no HAVING clause.