jamesfredley commented on code in PR #16875:
URL: https://github.com/apache/grails-core/pull/16875#discussion_r4495290665
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grails-datastore-core/src/main/groovy/org/grails/datastore/mapping/query/Query.java:
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@@ -691,6 +691,122 @@ protected FetchType fetchStrategy(String property) {
return FetchType.LAZY;
}
+ /**
+ * Runs the subqueries inside the given criteria and returns a copy of the
criteria that holds their
+ * results, for datastores that cannot evaluate a subquery themselves
(MongoDB, Neo4j). The criteria
+ * passed in are never changed, so a query that is executed twice runs its
subqueries twice.
+ *
+ * <p>A comparison ({@code ==}, {@code !=}, {@code >}, {@code >=}, {@code
<}, {@code <=}) against a
+ * subquery, such as {@code age > avg(age)}, takes the one value the
subquery returns, and {@code in}
+ * and {@code notIn} take all of them. A comparison against a subquery
that returns no row matches no row,
+ * as in SQL, where the comparison is unknown. A subquery that returns
more than one row for a comparison is
+ * rejected. Subqueries inside an association block are resolved too.
{@code exists}, {@code notExists} and the {@code all} and {@code some} forms
are rejected
+ * with an {@link InvalidDataAccessResourceUsageException}, as they are
not supported.</p>
+ *
+ * @param criteria the criteria of this query
+ * @return the same instance when it holds no subquery, otherwise a copy
with the subqueries resolved
+ * @throws InvalidDataAccessResourceUsageException for a form that cannot
be resolved
+ * @since 8.0.1
+ */
+ protected Junction resolveSubqueries(Junction criteria) {
+ return (Junction) resolveSubqueries((Criterion) criteria);
+ }
+
+ private Criterion resolveSubqueries(Criterion criterion) {
+ if (criterion instanceof Junction junction) {
+ List<Criterion> resolved = new
ArrayList<>(junction.getCriteria().size());
+ boolean changed = false;
+ for (Criterion nested : junction.getCriteria()) {
+ Criterion replacement = resolveSubqueries(nested);
+ changed |= replacement != nested;
+ resolved.add(replacement);
+ }
+ if (!changed) {
+ return junction;
+ }
+ if (junction instanceof Disjunction) {
+ return new Disjunction(resolved);
+ }
+ if (junction instanceof Negation) {
+ Negation negation = new Negation();
+ resolved.forEach(negation::add);
+ return negation;
+ }
+ return new Conjunction(resolved);
+ }
+ if (criterion instanceof Exists || criterion instanceof NotExists) {
+ throw unsupportedSubquery(criterion.getClass().getSimpleName());
+ }
+ if (criterion instanceof In in && in.getSubquery() != null) {
+ return new In(in.getProperty(), subqueryValues(in.getSubquery()));
+ }
+ if (criterion instanceof NotIn notIn) {
+ Negation negation = new Negation();
+ negation.add(new In(notIn.getProperty(),
subqueryValues(notIn.getSubquery())));
+ return negation;
+ }
+ if (criterion instanceof SubqueryCriterion) {
+ throw unsupportedSubquery(criterion.getClass().getSimpleName());
+ }
+ if (criterion instanceof AssociationQuery associationQuery) {
+ Junction nested = associationQuery.getCriteria();
+ Junction resolved = (Junction) resolveSubqueries((Criterion)
nested);
+ if (resolved == nested) {
+ return criterion;
+ }
+ AssociationQuery copy = new
AssociationQuery(associationQuery.getSession(), associationQuery.getEntity(),
+ associationQuery.getAssociation());
+ copy.criteria = resolved;
+ return copy;
+ }
+ if (criterion instanceof PropertyCriterion property &&
property.getValue() instanceof QueryableCriteria subquery) {
+ if (!(criterion instanceof Equals || criterion instanceof
NotEquals || criterion instanceof GreaterThan ||
+ criterion instanceof GreaterThanEquals || criterion
instanceof LessThan ||
+ criterion instanceof LessThanEquals)) {
+ throw
unsupportedSubquery(criterion.getClass().getSimpleName());
+ }
+ List<?> rows = subquery.list();
+ if (rows == null || rows.isEmpty()) {
Review Comment:
not { gt('age', Person.where { firstName == 'Absent' }.property('age')) }
replaces the empty subquery with age IN []. The negation is true, so every
person is returned. An empty scalar comparison should match no rows, including
under not.
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