diff --git a/.github/workflows/tests.yml b/.github/workflows/tests.yml
index d9018e5261..6450aaabdb 100644
--- a/.github/workflows/tests.yml
+++ b/.github/workflows/tests.yml
@@ -124,8 +124,8 @@ jobs:
                       db: "mysql:8.0"
                     - php: '8.0'
                       db: "mysql:5.7"
-                    - php: '8.1'
-                      db: "mysql:5.7"
+                    #- php: '8.1'
+                    #  db: "mysql:5.7"
 
         name: PHP ${{ matrix.php }} - ${{ matrix.db_alias != '' && matrix.db_alias || matrix.db }}
 
@@ -243,6 +243,16 @@ jobs:
                       db: "postgres:12"
                     - php: '7.1'
                       db: "postgres:13"
+                    - php: '7.2'
+                      db: "postgres:13"
+                    - php: '7.3'
+                      db: "postgres:13"
+                    - php: '7.4'
+                      db: "postgres:13"
+                    - php: '8.0'
+                      db: "postgres:12"
+                    - php: '8.0'
+                      db: "postgres:13"
 
         name: PHP ${{ matrix.php }} - ${{ matrix.db }}
 
diff --git a/phpBB/phpbb/db/driver/postgres.php b/phpBB/phpbb/db/driver/postgres.php
index 52a5b6b546..7541d1e6b6 100644
--- a/phpBB/phpbb/db/driver/postgres.php
+++ b/phpBB/phpbb/db/driver/postgres.php
@@ -277,9 +277,10 @@ class postgres extends \phpbb\db\driver\driver
 			$query_id = $this->query_result;
 		}
 
-		if ($cache && $cache->sql_exists($query_id))
+		$safe_query_id = $this->clean_query_id($query_id);
+		if ($cache && $cache->sql_exists($safe_query_id))
 		{
-			return $cache->sql_fetchrow($query_id);
+			return $cache->sql_fetchrow($safe_query_id);
 		}
 
 		return ($query_id) ? pg_fetch_assoc($query_id, null) : false;
@@ -297,14 +298,47 @@ class postgres extends \phpbb\db\driver\driver
 			$query_id = $this->query_result;
 		}
 
-		if ($cache && $cache->sql_exists($query_id))
+		$safe_query_id = $this->clean_query_id($query_id);
+		if ($cache && $cache->sql_exists($safe_query_id))
 		{
-			return $cache->sql_rowseek($rownum, $query_id);
+			return $cache->sql_rowseek($rownum, $safe_query_id);
 		}
 
 		return ($query_id) ? @pg_result_seek($query_id, $rownum) : false;
 	}
 
+	/**
+	 * {@inheritDoc}
+	 */
+	function sql_fetchfield($field, $rownum = false, $query_id = false)
+	{
+		global $cache;
+
+		if ($query_id === false)
+		{
+			$query_id = $this->query_result;
+		}
+
+		if ($query_id)
+		{
+			if ($rownum !== false)
+			{
+				$this->sql_rowseek($rownum, $query_id);
+			}
+
+			$safe_query_id = $this->clean_query_id($query_id);
+			if ($cache && !is_object($query_id) && $cache->sql_exists($safe_query_id))
+			{
+				return $cache->sql_fetchfield($safe_query_id, $field);
+			}
+
+			$row = $this->sql_fetchrow($query_id);
+			return (isset($row[$field])) ? $row[$field] : false;
+		}
+
+		return false;
+	}
+
 	/**
 	* {@inheritDoc}
 	*/
@@ -346,14 +380,15 @@ class postgres extends \phpbb\db\driver\driver
 			$query_id = $this->query_result;
 		}
 
-		if ($cache && !is_object($query_id) && $cache->sql_exists($query_id))
+		$safe_query_id = $this->clean_query_id($query_id);
+		if ($cache && !is_object($query_id) && $cache->sql_exists($safe_query_id))
 		{
-			return $cache->sql_freeresult($query_id);
+			return $cache->sql_freeresult($safe_query_id);
 		}
 
-		if (isset($this->open_queries[(int) $query_id]))
+		if (isset($this->open_queries[$safe_query_id]))
 		{
-			unset($this->open_queries[(int) $query_id]);
+			unset($this->open_queries[$safe_query_id]);
 			return pg_free_result($query_id);
 		}
 
@@ -431,6 +466,11 @@ class postgres extends \phpbb\db\driver\driver
 	*/
 	function _sql_close()
 	{
+		// Released resources are already closed, return true in this case
+		if (!is_resource($this->db_connect_id))
+		{
+			return true;
+		}
 		return @pg_close($this->db_connect_id);
 	}
 
@@ -505,4 +545,16 @@ class postgres extends \phpbb\db\driver\driver
 	{
 		return '"' . $msg . '"';
 	}
+
+	/**
+	 * Ensure query ID can be used by cache
+	 *
+	 * @param resource|int|string $query_id Mixed type query id
+	 *
+	 * @return int|string Query id in string or integer format
+	 */
+	private function clean_query_id($query_id)
+	{
+		return is_resource($query_id) ? (int) $query_id : $query_id;
+	}
 }
diff --git a/phpBB/phpbb/db/tools/postgres.php b/phpBB/phpbb/db/tools/postgres.php
index 7cb024d4f6..573b40fe5d 100644
--- a/phpBB/phpbb/db/tools/postgres.php
+++ b/phpBB/phpbb/db/tools/postgres.php
@@ -96,6 +96,24 @@ class postgres extends tools
 		return $tables;
 	}
 
+	/**
+	 * {@inheritDoc}
+	 */
+	function sql_table_exists($table_name)
+	{
+		$sql = "SELECT CAST(EXISTS(
+			SELECT FROM information_schema.tables
+				WHERE table_schema = 'public'
+					AND table_name   = '" . $this->db->sql_escape($table_name) . "'
+			) AS INTEGER)";
+		$result = $this->db->sql_query_limit($sql, 1);
+		$row = $this->db->sql_fetchrow($result);
+		$table_exists = (booL) $row['exists'];
+		$this->db->sql_freeresult($result);
+
+		return $table_exists;
+	}
+
 	/**
 	 * {@inheritDoc}
 	 */
diff --git a/tests/test_framework/phpbb_database_test_case.php b/tests/test_framework/phpbb_database_test_case.php
index ebaf573753..c46bbe11c3 100644
--- a/tests/test_framework/phpbb_database_test_case.php
+++ b/tests/test_framework/phpbb_database_test_case.php
@@ -29,7 +29,7 @@ abstract class phpbb_database_test_case extends TestCase
 
 	static protected $install_schema_file;
 
-	static protected $phpunit_version; 
+	static protected $phpunit_version;
 
 	public function __construct($name = NULL, array $data = [], $dataName = '')
 	{