This class represents the specifications for the joining operation in search.
Joins are only possible for matching on the qualified id of an outer document and a property value within a subquery document. In the subquery documents, these values may be referred to with a property path such as "email.recipient.id" or "entityId" or a property expression. One such property expression is "this.qualifiedId()", which refers to the document's combined package, database, namespace, and id.
Note that in order for perform the join, the property referred to by
getChildPropertyExpression()
has to be a property with
AppSearchSchema.StringPropertyConfig.getJoinableValueType()
set to
AppSearchSchema.StringPropertyConfig.JOINABLE_VALUE_TYPE_QUALIFIED_ID
. Otherwise
no documents will be joined to any SearchResult
.
Take these outer query and subquery results for example:
Outer result {
id: id1
score: 5
}
Subquery result 1 {
id: id2
score: 2
entityId: pkg$db/ns#id1
notes: This is some doc
}
Subquery result 2 {
id: id3
score: 3
entityId: pkg$db/ns#id2
notes: This is another doc
}
In this example, subquery result 1 contains a property "entityId" whose value is
"pkg$db/ns#id1", referring to the outer result. If you call JoinSpec.Builder
with "entityId", we will retrieve the value of the property "entityId" from the child
document, which is "pkg$db#ns/id1". Let's say the qualified id of the outer result is
"pkg$db#ns/id1". This would mean the subquery result 1 document will be matched to that
parent document. This is done by adding a SearchResult
containing the child document to the top-level parent SearchResult.getJoinedResults()
.
If
getChildPropertyExpression()
is "notes", we will check the values of the notes
property in the subquery results. In subquery result 1, this values is "This is some doc",
which does not equal the qualified id of the outer query result. As such, subquery result 1
will not be joined to the outer query result.
It's possible to define an advanced ranking strategy in the nested SearchSpec
and also use
SearchSpec.RANKING_STRATEGY_JOIN_AGGREGATE_SCORE
in the outer SearchSpec
.
In this case, the parents will be ranked based on an aggregation, such as the sum, of the
signals calculated by scoring the joined documents with the advanced ranking strategy.
In terms of scoring, if
SearchSpec.RANKING_STRATEGY_JOIN_AGGREGATE_SCORE
is set in SearchSpec.getRankingStrategy()
,
the scores of the outer SearchResults can be influenced by the ranking signals of the
subquery results. For example, if the
getAggregationScoringStrategy()
is set to:
AGGREGATION_SCORING_MIN_RANKING_SIGNAL
, the ranking signal of the outerSearchResult
will be set to the minimum of the ranking signals of the subquery results. In this case, it will be the minimum of 2 and 3, which is 2.AGGREGATION_SCORING_MAX_RANKING_SIGNAL
, the ranking signal of the outerSearchResult
will be 3.AGGREGATION_SCORING_AVG_RANKING_SIGNAL
, the ranking signal of the outerSearchResult
will be 2.5.AGGREGATION_SCORING_RESULT_COUNT
, the ranking signal of the outerSearchResult
will be 2 as there are two joined results.AGGREGATION_SCORING_SUM_RANKING_SIGNAL
, the ranking signal of the outerSearchResult
will be 5, the sum of 2 and 3.AGGREGATION_SCORING_OUTER_RESULT_RANKING_SIGNAL
, the ranking signal of the outerSearchResult
will stay as it is.
Referring to "this.childrenRankingSignals()" in the ranking signal of the outer query will
return the signals calculated by scoring the joined documents using the scoring strategy in
the nested SearchSpec
,
as in SearchResult.getRankingSignal()
.
Nested Class Summary
class | JoinSpec.Builder | Builder for objects . |
Constant Summary
int | AGGREGATION_SCORING_AVG_RANKING_SIGNAL | Score the aggregation of joined documents using the average ranking signal. |
int | AGGREGATION_SCORING_MAX_RANKING_SIGNAL | Score the aggregation of joined documents using the largest ranking signal. |
int | AGGREGATION_SCORING_MIN_RANKING_SIGNAL | Score the aggregation of joined documents using the smallest ranking signal. |
int | AGGREGATION_SCORING_OUTER_RESULT_RANKING_SIGNAL | Do not score the aggregation of joined documents. |
int | AGGREGATION_SCORING_RESULT_COUNT | Score the aggregation of joined documents by counting the number of results. |
int | AGGREGATION_SCORING_SUM_RANKING_SIGNAL | Score the aggregation of joined documents using the sum of ranking signal. |
Inherited Constant Summary
Field Summary
public static final Creator<JoinSpec> | CREATOR | Creator class for JoinSpec . |
Public Method Summary
int |
getAggregationScoringStrategy()
Gets the joined document list scoring strategy.
|
String |
getChildPropertyExpression()
The property expression that is used to get values from child documents,
returned from the nested search.
|
int |
getMaxJoinedResultCount()
Returns the max amount of
SearchResult
objects to return with the parent document, with a default of 10 SearchResults.
|
String |
getNestedQuery()
Returns the query to run on the joined documents.
|
SearchSpec |
getNestedSearchSpec()
Returns the search spec used to retrieve the joined documents.
|
void |
writeToParcel(Parcel dest, int
flags)
|
Inherited Method Summary
Constants
public static final int AGGREGATION_SCORING_AVG_RANKING_SIGNAL
Score the aggregation of joined documents using the average ranking signal.
public static final int AGGREGATION_SCORING_MAX_RANKING_SIGNAL
Score the aggregation of joined documents using the largest ranking signal.
public static final int AGGREGATION_SCORING_MIN_RANKING_SIGNAL
Score the aggregation of joined documents using the smallest ranking signal.
public static final int AGGREGATION_SCORING_OUTER_RESULT_RANKING_SIGNAL
Do not score the aggregation of joined documents. This is for the case where we want to perform a join, but keep the parent ranking signal.
public static final int AGGREGATION_SCORING_RESULT_COUNT
Score the aggregation of joined documents by counting the number of results.
public static final int AGGREGATION_SCORING_SUM_RANKING_SIGNAL
Score the aggregation of joined documents using the sum of ranking signal.
Fields
Public Methods
public int getAggregationScoringStrategy ()
Gets the joined document list scoring strategy.
The default scoring strategy is
AGGREGATION_SCORING_OUTER_RESULT_RANKING_SIGNAL
, which specifies that the
score of the outer parent document will be used.
public String getChildPropertyExpression ()
The property expression that is used to get values from child documents, returned from the nested search. These values are then used to match them to parent documents. These are analogous to foreign keys.
Returns
- the property expression to match in the child documents.
See Also
public int getMaxJoinedResultCount ()
Returns the max amount of SearchResult
objects to return with the parent document, with a default of 10 SearchResults.
public String getNestedQuery ()
Returns the query to run on the joined documents.
public SearchSpec getNestedSearchSpec ()
Returns the search spec used to retrieve the joined documents.
If
JoinSpec.Builder.setNestedSearch(String, SearchSpec)
is never called, this
will return a SearchSpec
with all default values. This will match every document, as the nested search query
will be "" and no schema will be filtered out.