com.bigdata.bop.join

Interface HashJoinAnnotations

All Known Subinterfaces:

HashIndexOp.Annotations, HashIndexOpBase.Annotations, HashJoinOp.Annotations, HTreeHashJoinAnnotations, HTreeHashJoinOp.Annotations, HTreeMergeJoin.Annotations, HTreeNamedSubqueryOp.Annotations, JVMHashJoinAnnotations, JVMHashJoinOp.Annotations, JVMMergeJoin.Annotations, JVMNamedSubqueryOp.Annotations, PipelinedHashIndexAndSolutionSetJoinOp.Annotations

public interface HashJoinAnnotations

Annotations for hash joins.

Version:

$Id$

Author:

Bryan Thompson

Field Summary

Fields

Modifier and Type	Field and Description
static String	ASK_VAR When non-null, the IVariable which will be bound to true iff there is at least one solution for a JoinTypeEnum.Exists hash join.
static long	DEFAULT_NO_JOIN_VARS_LIMIT TODO Annotation and query hint for this.
static String	JOIN_VARS The IVariable[] specifying the join variables (required).
static String	OUTPUT_DISTINCT_JVs Boolean flag to be set when we do not want to return the variables defined by the {#JVMHashIndexOp.Annotations.SELECT} annotation, but instead calculate the DISTINCT projection over the join variables.

Field Detail

JOIN_VARS

static final String JOIN_VARS

The IVariable[] specifying the join variables (required). The order of the entries is used when forming the as-bound keys for the hash table. Duplicate elements and null elements are not permitted.

Note: The source solutions presented to a hash join MUST have bindings for the JOIN_VARS in order to join (source solutions can still be passed on as optionals, but they will not join unless the join variables are not bound).

Note: If no join variables are specified, then the join will consider the N x M cross product, filtering for solutions which join. This is very expensive when compared to a hash join. Whenever possible you should identify one or more variables which must be bound for the join and specify those as the join variables.

ASK_VAR

static final String ASK_VAR

When non-null, the IVariable which will be bound to true iff there is at least one solution for a JoinTypeEnum.Exists hash join.

Note: This supports the bridge between the evaluation of the (NOT) EXISTS graph pattern and the processing whether or not the "EXISTS" graph pattern was successful, which is encoded on the "ask variable."

DEFAULT_NO_JOIN_VARS_LIMIT

static final long DEFAULT_NO_JOIN_VARS_LIMIT

TODO Annotation and query hint for this.

See Also:

UnconstrainedJoinException, Constant Field Values

OUTPUT_DISTINCT_JVs

static final String OUTPUT_DISTINCT_JVs

Boolean flag to be set when we do not want to return the variables defined by the {#JVMHashIndexOp.Annotations.SELECT} annotation, but instead calculate the DISTINCT projection over the join variables. This is the approach that we use for many subgroups, where we project in the distinct variables (typically: exactly the join variables), execute the inner group, and finally rejoin with the whole set of variables in the end.