PostgreSQL Integration improvments

.flake8

@@ -160,6 +160,5 @@ exclude =
   mindsdb/integrations/handlers/aurora_handler/*
   mindsdb/integrations/handlers/surrealdb_handler/*
   mindsdb/integrations/handlers/neuralforecast_handler/*
-  mindsdb/integrations/handlers/postgres_handler/*
   mindsdb/integrations/handlers/rag_handler/*
 max-complexity = 18

.github/workflows/mindsdb.yml

@@ -130,3 +130,6 @@ jobs:
         CHECK_FOR_UPDATES: False
         OPENAI_API_KEY: ${{secrets.OPENAI_API_KEY}}
         ANYSCALE_ENDPOINTS_API_KEY: ${{secrets.ANYSCALE_ENDPOINTS_API_KEY}}
+    - name: Run Integrations unittest
+      run: |
+        python -m unittest discover -s tests/unit/handlers 

mindsdb/integrations/handlers/postgres_handler/README.md

@@ -0,0 +1,63 @@
+# PostgreSQL Integration
+
+This documentation describes the integration of MindsDB with PostgreSQL, a powerful, open-source, object-relational database system. The integration allows for advanced SQL functionalities, extending PostgreSQL's capabilities with MindsDB's features.
+
+## Getting Started
+
+### Prerequisites
+
+   1. Ensure that MindsDB and PostgreSQL are installed on your system or you have access to cloud options.
+   2. If running locally install the dependencies as `pip install mindsdb[postgres]`.
+
+
+### Connection
+
+Use the following syntax to create a connection to the PostgreSQL database in MindsDB:
+
+```sql
+    CREATE DATABASE psql_datasource 
+    WITH ENGINE = 'postgres', 
+    PARAMETERS = {
+        "host": "127.0.0.1",
+        "port": 5432,
+        "database": "postgres",
+        "user": "postgres",
+        "schema": "data",
+        "password": "password"
+    };
+```
+
+Required Parameters:
+
+* `user`: The username for the PostgreSQL database.
+* `password`: The password for the PostgreSQL database.
+* `host`: The hostname, IP address, or URL of the PostgreSQL server.
+* `port`: The port number for connecting to the PostgreSQL server.
+* `database`: The name of the PostgreSQL database to connect to.
+
+Optional Parameters:
+
+* `schema`: The database schema to use. Default is `public`.
+* `sslmode`: The SSL mode for the connection.
+
+### Example Usage
+
+Querying a Table:
+
+ ```sql
+    SELECT * FROM psql_datasource.demo_data.used_car_price LIMIT 10;
+```
+
+Running native queries by wrapping them inside the postgresql integration SELECT:
+
+```sql
+SELECT * FROM psql_datasource (
+    --Native Query Goes Here
+     SELECT 
+        model, 
+        COUNT(*) OVER (PARTITION BY model, year) AS units_to_sell, 
+        ROUND((CAST(tax AS decimal) / price), 3) AS tax_div_price
+    FROM demo_data.used_car_price
+);
+```
+> Note: In the above examples we are using `psql_datasource` name, which was created with CREATE DATABASE query.

mindsdb/integrations/handlers/postgres_handler/postgres_handler.py

@@ -21,6 +21,7 @@
 
 logger = log.getLogger(__name__)
 
+
 class PostgresHandler(DatabaseHandler):
     """
     This handler handles connection and execution of the PostgreSQL statements.
@@ -40,15 +41,21 @@ def __init__(self, name=None, **kwargs):
         self.is_connected = False
 
     def __del__(self):
-        if self.is_connected is True:
+        if self.is_connected:
             self.disconnect()
 
     @profiler.profile()
     def connect(self):
         """
-        Handles the connection to a PostgreSQL database instance.
+        Establishes a connection to a PostgreSQL database.
+
+        Raises:
+            psycopg.Error: If an error occurs while connecting to the PostgreSQL database.
+
+        Returns:
+            psycopg.Connection: A connection object to the PostgreSQL database.
         """
-        if self.is_connected is True:
+        if self.is_connected:
             return self.connection
 
         config = {
@@ -62,48 +69,58 @@ def connect(self):
         if self.connection_args.get('sslmode'):
             config['sslmode'] = self.connection_args.get('sslmode')
 
+        # If schema is not provided set public as default one
         if self.connection_args.get('schema'):
             config['options'] = f'-c search_path={self.connection_args.get("schema")},public'
 
-        connection = psycopg.connect(**config, connect_timeout=10)
-
-        self.is_connected = True
-        self.connection = connection
-        return self.connection
+        try:
+            self.connection = psycopg.connect(**config, connect_timeout=10)
+            self.is_connected = True
+            return self.connection
+        except psycopg.Error as e:
+            logger.error(f'Error connecting to PostgreSQL {self.database}, {e}!')
+            self.is_connected = False
+            raise
 
     def disconnect(self):
-        if self.is_connected is False:
+        """
+        Closes the connection to the PostgreSQL database if it's currently open.
+        """
+        if not self.is_connected:
             return
         self.connection.close()
         self.is_connected = False
 
     def check_connection(self) -> StatusResponse:
         """
-        Check the connection of the PostgreSQL database
-        :return: success status and error message if error occurs
+        Checks the status of the connection to the PostgreSQL database.
+
+        Returns:
+            StatusResponse: An object containing the success status and an error message if an error occurs.
         """
         response = StatusResponse(False)
-        need_to_close = self.is_connected is False
+        need_to_close = not self.is_connected
 
         try:
             connection = self.connect()
             with connection.cursor() as cur:
+                # Execute a simple query to test the connection
                 cur.execute('select 1;')
             response.success = True
         except psycopg.Error as e:
             logger.error(f'Error connecting to PostgreSQL {self.database}, {e}!')
-            response.error_message = e
+            response.error_message = str(e)
 
-        if response.success is True and need_to_close:
+        if response.success and need_to_close:
             self.disconnect()
-        if response.success is False and self.is_connected is True:
+        elif not response.success and self.is_connected:
             self.is_connected = False
 
         return response
 
     def _cast_dtypes(self, df: DataFrame, description: list) -> None:
-        """ Cast df dtypes basing on postgres types
-
+        """
+        Cast df dtypes basing on postgres types
             Note:
                 Date types casting is not provided because of there is no issues (so far).
                 By default pandas will cast postgres date types to:
@@ -130,16 +147,24 @@ def _cast_dtypes(self, df: DataFrame, description: list) -> None:
             if str(col.dtype) == 'object':
                 pg_type = types.get(description[column_index].type_code)
                 if pg_type is not None and pg_type.name in types_map:
-                    df.iloc[:, column_index] = col.astype(types_map[pg_type.name])
+                    col = col.fillna(0)
+                    try:
+                        df.iloc[:, column_index] = col.astype(types_map[pg_type.name])
+                    except ValueError as e:
+                        logger.error(f'Error casting column {col.name} to {types_map[pg_type.name]}: {e}')
 
     @profiler.profile()
     def native_query(self, query: str) -> Response:
         """
-        Receive SQL query and runs it
-        :param query: The SQL query to run in PostgreSQL
-        :return: returns the records from the current recordset
+        Executes a SQL query on the PostgreSQL database and returns the result.
+
+        Args:
+            query (str): The SQL query to be executed.
+
+        Returns:
+            Response: A response object containing the result of the query or an error message.
         """
-        need_to_close = self.is_connected is False
+        need_to_close = not self.is_connected
 
         connection = self.connect()
         with connection.cursor() as cur:
@@ -160,30 +185,39 @@ def native_query(self, query: str) -> Response:
                     )
                 connection.commit()
             except Exception as e:
-                logger.error(f'Error running query: {query} on {self.database}!')
+                logger.error(f'Error running query: {query} on {self.database}, {e}!')
                 response = Response(
                     RESPONSE_TYPE.ERROR,
                     error_code=0,
                     error_message=str(e)
                 )
                 connection.rollback()
 
-        if need_to_close is True:
+        if need_to_close:
             self.disconnect()
-
         return response
 
     @profiler.profile()
     def query(self, query: ASTNode) -> Response:
         """
-        Retrieve the data from the SQL statement with eliminated rows that dont satisfy the WHERE condition
+        Executes a SQL query represented by an ASTNode and retrieves the data.
+
+        Args:
+            query (ASTNode): An ASTNode representing the SQL query to be executed.
+
+        Returns:
+            Response: The response from the `native_query` method, containing the result of the SQL query execution.
         """
         query_str = self.renderer.get_string(query, with_failback=True)
+        logger.debug(f"Executing SQL query: {query_str}")
         return self.native_query(query_str)
 
     def get_tables(self) -> Response:
         """
-        List all tables in PostgreSQL without the system tables information_schema and pg_catalog
+        Retrieves a list of all non-system tables and views in the current schema of the PostgreSQL database.
+
+        Returns:
+            Response: A response object containing the list of tables and views, formatted as per the `Response` class.
         """
         query = """
             SELECT
@@ -200,6 +234,21 @@ def get_tables(self) -> Response:
         return self.native_query(query)
 
     def get_columns(self, table_name: str) -> Response:
+        """
+        Retrieves column details for a specified table in the PostgreSQL database.
+
+        Args:
+            table_name (str): The name of the table for which to retrieve column information.
+
+        Returns:
+            Response: A response object containing the column details, formatted as per the `Response` class.
+        Raises:
+            ValueError: If the 'table_name' is not a valid string.
+        """
+
+        if not table_name or not isinstance(table_name, str):
+            raise ValueError("Invalid table name provided.")
+
         query = f"""
             SELECT
                 column_name as "Field",
@@ -211,6 +260,7 @@ def get_columns(self, table_name: str) -> Response:
         """
         return self.native_query(query)
 
+
 connection_args = OrderedDict(
     user={
         'type': ARG_TYPE.STR,
@@ -260,6 +310,7 @@ def get_columns(self, table_name: str) -> Response:
     host='127.0.0.1',
     port=5432,
     user='root',
+    schema='public',
     password='password',
     database='database'
 )