Examples with ExpressionScopingVisitor com.yahoo.elide.core.filter.expression.ExpressionScopingVisitor used on opensource projects

Example 1 with ExpressionScopingVisitor

use of com.yahoo.elide.core.filter.expression.ExpressionScopingVisitor in project elide by yahoo.

the class SubCollectionPageTotalsQueryBuilder method build.

/**
 * Constructs a query that returns the count of the members of a relationship.
 *
 * For a relationship like author#3.books, constructs a query like:
 *
 * SELECT COUNT(DISTINCT Author_books)
 * FROM Author AS Author JOIN Author.books AS Author_books
 * WHERE Author.id = :author_books_id;
 *
 * Rather than query relationship directly (FROM Book), this query starts at the relationship
 * owner to support scenarios where there is no inverse relationship from the relationship back to
 * the owner.
 *
 * @return the constructed query
 */
@Override
public Query build() {
    Type<?> parentType = dictionary.lookupEntityClass(relationship.getParentType());
    Type<?> idType = dictionary.getIdType(parentType);
    Object idVal = CoerceUtil.coerce(dictionary.getId(relationship.getParent()), idType);
    String idField = dictionary.getIdFieldName(parentType);
    // Construct a predicate that selects an individual element of the relationship's parent (Author.id = 3).
    FilterPredicate idExpression = new InPredicate(new PathElement(parentType, idType, idField), idVal);
    Collection<FilterPredicate> predicates = new ArrayList<>();
    String joinClause = "";
    String filterClause = "";
    String relationshipName = relationship.getRelationshipName();
    // Relationship alias is Author_books
    String parentAlias = getTypeAlias(parentType);
    String relationshipAlias = appendAlias(parentAlias, relationshipName);
    FilterExpression filterExpression = entityProjection.getFilterExpression();
    if (filterExpression != null) {
        // Copy and scope the filter expression for the join clause
        ExpressionScopingVisitor visitor = new ExpressionScopingVisitor(new PathElement(parentType, relationship.getChildType(), relationship.getRelationshipName()));
        FilterExpression scoped = filterExpression.accept(visitor);
        // For each filter predicate, prepend the predicate with the parent:
        // books.title = 'Foobar' becomes author.books.title = 'Foobar'
        PredicateExtractionVisitor extractor = new PredicateExtractionVisitor(new ArrayList<>());
        predicates = scoped.accept(extractor);
        predicates.add(idExpression);
        // Join together the provided filter expression with the expression which selects the collection owner.
        FilterExpression joinedExpression = new AndFilterExpression(scoped, idExpression);
        // Build the JOIN clause from the filter predicate
        joinClause = getJoinClauseFromFilters(joinedExpression, true);
        // Build the WHERE clause
        filterClause = new FilterTranslator(dictionary).apply(joinedExpression, USE_ALIAS);
    } else {
        // If there is no filter, we still need to explicitly JOIN book and authors.
        joinClause = JOIN + parentAlias + PERIOD + relationshipName + SPACE + relationshipAlias + SPACE;
        filterClause = new FilterTranslator(dictionary).apply(idExpression, USE_ALIAS);
        predicates.add(idExpression);
    }
    Query query = session.createQuery("SELECT COUNT(DISTINCT " + relationshipAlias + ") " + FROM + parentType.getCanonicalName() + AS + parentAlias + SPACE + joinClause + WHERE + filterClause);
    // Fill in the query parameters
    supplyFilterQueryParameters(query, predicates);
    return query;
}