Update postgresql lib (#546)

Signed-off-by: Marcelo Henrique Neppel <[email protected]>

lib/charms/postgresql_k8s/v0/postgresql.py

@@ -36,7 +36,7 @@
 
 # Increment this PATCH version before using `charmcraft publish-lib` or reset
 # to 0 if you are raising the major API version
-LIBPATCH = 29
+LIBPATCH = 30
 
 INVALID_EXTRA_USER_ROLE_BLOCKING_MESSAGE = "invalid role(s) for extra user roles"
 
@@ -79,6 +79,10 @@ class PostgreSQLEnableDisableExtensionError(Exception):
     """Exception raised when enabling/disabling an extension fails."""
 
 
+class PostgreSQLGetLastArchivedWALError(Exception):
+    """Exception raised when retrieving last archived WAL fails."""
+
+
 class PostgreSQLGetPostgreSQLVersionError(Exception):
     """Exception raised when retrieving PostgreSQL version fails."""
 
@@ -383,6 +387,16 @@ def _generate_database_privileges_statements(
                 )
         return statements
 
+    def get_last_archived_wal(self) -> str:
+        """Get the name of the last archived wal for the current PostgreSQL cluster."""
+        try:
+            with self._connect_to_database() as connection, connection.cursor() as cursor:
+                cursor.execute("SELECT last_archived_wal FROM pg_stat_archiver;")
+                return cursor.fetchone()[0]
+        except psycopg2.Error as e:
+            logger.error(f"Failed to get PostgreSQL last archived WAL: {e}")
+            raise PostgreSQLGetLastArchivedWALError()
+
     def get_postgresql_text_search_configs(self) -> Set[str]:
         """Returns the PostgreSQL available text search configs.
 

tests/unit/test_postgresql.py

@@ -4,7 +4,10 @@
 
 import psycopg2
 import pytest
-from charms.postgresql_k8s.v0.postgresql import PostgreSQLCreateDatabaseError
+from charms.postgresql_k8s.v0.postgresql import (
+    PostgreSQLCreateDatabaseError,
+    PostgreSQLGetLastArchivedWALError,
+)
 from ops.testing import Harness
 from psycopg2.sql import SQL, Composed, Identifier
 
@@ -232,6 +235,29 @@ def test_generate_database_privileges_statements(harness):
     ]
 
 
+def test_get_last_archived_wal(harness):
+    with patch(
+        "charms.postgresql_k8s.v0.postgresql.PostgreSQL._connect_to_database"
+    ) as _connect_to_database:
+        # Test a successful call.
+        execute = _connect_to_database.return_value.__enter__.return_value.cursor.return_value.__enter__.return_value.execute
+        _connect_to_database.return_value.__enter__.return_value.cursor.return_value.__enter__.return_value.fetchone.return_value = (
+            "000000010000000100000001",
+        )
+        assert harness.charm.postgresql.get_last_archived_wal() == "000000010000000100000001"
+        execute.assert_called_once_with("SELECT last_archived_wal FROM pg_stat_archiver;")
+
+        # Test a failed call.
+        execute.reset_mock()
+        execute.side_effect = psycopg2.Error
+        try:
+            harness.charm.postgresql.get_last_archived_wal()
+            assert False
+        except PostgreSQLGetLastArchivedWALError:
+            pass
+        execute.assert_called_once_with("SELECT last_archived_wal FROM pg_stat_archiver;")
+
+
 def test_build_postgresql_parameters(harness):
     # Test when not limit is imposed to the available memory.
     config_options = {