Implement countDocs from DocumentStore interface

src/PostgresDocumentStore.php

@@ -524,6 +524,29 @@ public function filterDocs(string $collectionName, Filter $filter, int $skip = n
         }
     }
 
+    /**
+     * @param string $collectionName
+     * @param Filter $filter
+     * @return int number of docs
+     */
+    public function countDocs(string $collectionName, Filter $filter): int
+    {
+        [$filterStr, $args] = $this->filterToWhereClause($filter);
+
+        $where = $filterStr? "WHERE $filterStr" : '';
+
+        $query = <<<EOT
+SELECT count(doc) 
+FROM {$this->schemaName($collectionName)}.{$this->tableName($collectionName)}
+$where;
+EOT;
+        $stmt = $this->connection->prepare($query);
+
+        $stmt->execute($args);
+
+        return (int) $stmt->fetchColumn(0);
+    }
+
     private function transactional(callable $callback)
     {
         if($this->manageTransactions) {

tests/PostgresDocumentStoreTest.php

@@ -434,6 +434,32 @@ public function it_handles_not_filter_nested_in_and_filter()
         $this->assertEquals([$thirdDocId], $refs);
     }
 
+    /**
+     * @test
+     */
+    public function it_counts_any_of_filter()
+    {
+        $collectionName = 'test_any_of_filter';
+        $this->documentStore->addCollection($collectionName);
+
+        $doc1 = ["foo" => "bar"];
+        $doc2 = ["foo" => "baz"];
+        $doc3 = ["foo" => "bat"];
+
+        $docs = [$doc1, $doc2, $doc3];
+
+        array_walk($docs, function (array $doc) use ($collectionName) {
+            $this->documentStore->addDoc($collectionName, Uuid::uuid4()->toString(), $doc);
+        });
+
+        $count = $this->documentStore->countDocs(
+            $collectionName,
+            new AnyOfFilter("foo", ["bar", "bat"])
+        );
+
+        $this->assertSame(2, $count);
+    }
+
     private function getIndexes(string $collectionName): array
     {
         return TestUtil::getIndexes($this->connection, self::TABLE_PREFIX.$collectionName);