select exists for repositories trait

Author: pfilsx

README.md

@@ -18,6 +18,7 @@ Features
 * Fix creating [default schema in down migrations for pgsql](https://github.com/doctrine/dbal/issues/1110)
 * [JSON(B) functions](https://www.postgresql.org/docs/current/functions-json.html) (in progress)
 * JSON(B) types based on object models (in progress, requires symfony/serializer)
+* [Trait](src/ORM/Trait/ExistsMethodRepositoryTrait.php) for easy use of [SELECT EXISTS(...)](https://www.postgresql.org/docs/current/functions-subquery.html#FUNCTIONS-SUBQUERY-EXISTS) in your entity repositories
 
 Requirement
 -----------

src/ORM/Trait/ExistsMethodRepositoryTrait.php

@@ -0,0 +1,58 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Pfilsx\PostgreSQLDoctrine\ORM\Trait;
+
+use Doctrine\DBAL\Exception;
+
+trait ExistsMethodRepositoryTrait
+{
+    /**
+     * @param array<string, mixed> $predicates
+     *
+     * @throws Exception
+     *
+     * @return bool
+     */
+    public function exists(array $predicates): bool
+    {
+        $subQb = $this->createQueryBuilder('_sub')->select('1');
+
+        $parameters = [];
+        $idx = 1;
+        foreach ($predicates as $field => $value) {
+            if (\is_array($value)) {
+                $subQb->andWhere($subQb->expr()->in("_sub.$field", $value));
+
+                continue;
+            }
+
+            if (\is_null($value)) {
+                $subQb->andWhere($subQb->expr()->isNull("_sub.$field"));
+
+                continue;
+            }
+
+            if (\is_object($value)) {
+                if (!\method_exists($value, 'getId')) {
+                    throw new \RuntimeException("Unable to cast object predicate value to scalar for key: $field");
+                }
+
+                $value = $value->getId();
+            }
+
+            $subQb->andWhere("_sub.$field = ?$idx");
+            $parameters[$idx] = $value;
+            ++$idx;
+        }
+
+        return (bool) $this->_em
+            ->getConnection()
+            ->createQueryBuilder()
+            ->select("EXISTS({$subQb->getQuery()->getSQL()})")
+            ->setParameters($parameters)
+            ->fetchOne()
+        ;
+    }
+}