diff --git a/src/PgSqlResultSet.php b/src/PgSqlResultSet.php
index 682f3c2..d2d1997 100644
--- a/src/PgSqlResultSet.php
+++ b/src/PgSqlResultSet.php
@@ -17,6 +17,9 @@ final class PgSqlResultSet implements Result
     /** @var int */
     private $position = 0;
 
+    /** @var int */
+    private $rowCount;
+
     /** @var int[] */
     private $fieldTypes = [];
 
@@ -36,6 +39,7 @@ final class PgSqlResultSet implements Result
     public function __construct($handle, Promise $nextResult)
     {
         $this->handle = $handle;
+        $this->rowCount = \pg_num_rows($this->handle);
         $this->nextResult = $nextResult;
 
         $numFields = \pg_num_fields($this->handle);
@@ -66,7 +70,7 @@ final class PgSqlResultSet implements Result
             return new Failure(new DisposedException);
         }
 
-        if (++$this->position > \pg_num_rows($this->handle)) {
+        if (++$this->position > $this->rowCount) {
             return new Success(null);
         }
 
@@ -74,21 +78,23 @@ final class PgSqlResultSet implements Result
 
         if ($result === false) {
             $message = \pg_result_error($this->handle);
-            \pg_free_result($this->handle);
             return new Failure(new FailureException($message));
         }
 
         try {
             return new Success($this->processRow($result));
         } catch (\Throwable $exception) {
-            \pg_free_result($this->handle);
-            $this->handle = null;
             return new Failure($exception);
         }
     }
 
     public function dispose(): void
     {
+        if ($this->handle === null) {
+            return;
+        }
+
+        \pg_free_result($this->handle);
         $this->handle = null;
     }
 
@@ -237,6 +243,6 @@ final class PgSqlResultSet implements Result
      */
     public function getRowCount(): int
     {
-        return \pg_num_rows($this->handle);
+        return $this->rowCount;
     }
 }
diff --git a/src/PqBufferedResultSet.php b/src/PqBufferedResultSet.php
index 0b377a9..ae1757e 100644
--- a/src/PqBufferedResultSet.php
+++ b/src/PqBufferedResultSet.php
@@ -17,16 +17,20 @@ final class PqBufferedResultSet implements Result
     /** @var int */
     private $position = 0;
 
-    /** @var Promise<ResultSet|null> */
+    /** @var int */
+    private $rowCount;
+
+    /** @var Promise<Result|null> */
     private $nextResult;
 
     /**
      * @param pq\Result $result PostgreSQL result object.
-     * @param Promise<ResultSet|null> $nextResult Promise for next result set.
+     * @param Promise<Result|null> $nextResult Promise for next result set.
      */
     public function __construct(pq\Result $result, Promise $nextResult)
     {
         $this->result = $result;
+        $this->rowCount = $result->numRows;
         $this->result->autoConvert = pq\Result::CONV_SCALAR | pq\Result::CONV_ARRAY;
         $this->nextResult = $nextResult;
     }
@@ -68,6 +72,6 @@ final class PqBufferedResultSet implements Result
      */
     public function getRowCount(): int
     {
-        return $this->result->numRows;
+        return $this->rowCount;
     }
 }
diff --git a/src/PqUnbufferedResultSet.php b/src/PqUnbufferedResultSet.php
index e94c8ca..ee5a4de 100644
--- a/src/PqUnbufferedResultSet.php
+++ b/src/PqUnbufferedResultSet.php
@@ -17,19 +17,19 @@ final class PqUnbufferedResultSet implements Result
     private $nextResult;
 
     /**
-     * @param callable():Promise<\pq\Result|Result|null> $fetch Function to fetch next result row.
-     * @param \pq\Result $result Initial PostgreSQL result object.
+     * @param callable():Promise<\pq\Result|null> $fetch Function to fetch next result row.
+     * @param \pq\Result $result Initial pq\Result result object.
      * @param Promise<Result|null> $nextResult
      */
     public function __construct(callable $fetch, pq\Result $result, Promise $nextResult)
     {
         $this->nextResult = $nextResult;
-        $this->generator = new AsyncGenerator(static function (callable $yield) use ($result, $fetch): \Generator {
+        $this->generator = new AsyncGenerator(static function (callable $emit) use ($result, $fetch): \Generator {
             try {
                 do {
                     $promise = $fetch();
                     $result->autoConvert = pq\Result::CONV_SCALAR | pq\Result::CONV_ARRAY;
-                    yield $yield($result->fetchRow(pq\Result::FETCH_ASSOC));
+                    yield $emit($result->fetchRow(pq\Result::FETCH_ASSOC));
                     $result = yield $promise;
                 } while ($result instanceof pq\Result);
             } catch (DisposedException $exception) {