Fix: Add RetryingPooledPostgresqlDatabase to handle max_retries param (#10524)

## What problem does this PR solve?

Fixes the PostgreSQL connection error that prevents RAGFlow from
starting:

peewee.ProgrammingError: invalid dsn: invalid connection option
"max_retries"


## Problem Analysis

The `BaseDataBase` class in `api/db/db_models.py` adds `max_retries` and
`retry_delay` to the database configuration dict before passing it to
the database connection constructor.

- **MySQL**: Has `RetryingPooledMySQLDatabase` class that properly
extracts these custom parameters using `kwargs.pop()` before calling the
parent constructor
- **PostgreSQL**: Was using the base `PooledPostgresqlDatabase` class
which passes all parameters directly to `psycopg2.connect()`, which
doesn't recognize `max_retries` as a valid connection option

## Solution

Created `RetryingPooledPostgresqlDatabase` class that:
- Extracts `max_retries` and `retry_delay` parameters before
initialization
- Implements retry logic with exponential backoff for connection
failures
- Handles PostgreSQL-specific connection errors (connection refused,
server closed, etc.)
- Mirrors the existing `RetryingPooledMySQLDatabase` implementation

Updated the `PooledDatabase` enum to use the new retrying class for
PostgreSQL.

## Benefits

✅ Prevents invalid connection parameters from being passed to psycopg2  
✅ Adds automatic retry logic for PostgreSQL connection failures  
✅ Provides better error logging for PostgreSQL-specific issues  
✅ Maintains consistency between MySQL and PostgreSQL database handling  

## Type of change

- [x] Bug Fix (non-breaking change which fixes an issue)

## Testing

Tested with PostgreSQL database configuration and verified:
- Server starts without the "invalid dsn" error
- Database connections are established successfully
- Retry logic works correctly on connection failures

Co-authored-by: Andrea Bugeja <andrea.bugeja@gig.com>

api/db/db_models.py

@@ -313,9 +313,75 @@ class RetryingPooledMySQLDatabase(PooledMySQLDatabase):
                     raise
 
 
+class RetryingPooledPostgresqlDatabase(PooledPostgresqlDatabase):
+    def __init__(self, *args, **kwargs):
+        self.max_retries = kwargs.pop("max_retries", 5)
+        self.retry_delay = kwargs.pop("retry_delay", 1)
+        super().__init__(*args, **kwargs)
+
+    def execute_sql(self, sql, params=None, commit=True):
+        for attempt in range(self.max_retries + 1):
+            try:
+                return super().execute_sql(sql, params, commit)
+            except (OperationalError, InterfaceError) as e:
+                # PostgreSQL specific error codes
+                # 57P01: admin_shutdown
+                # 57P02: crash_shutdown
+                # 57P03: cannot_connect_now
+                # 08006: connection_failure
+                # 08003: connection_does_not_exist
+                # 08000: connection_exception
+                error_messages = ['connection', 'server closed', 'connection refused', 
+                                'no connection to the server', 'terminating connection']
+                
+                should_retry = any(msg in str(e).lower() for msg in error_messages)
+
+                if should_retry and attempt < self.max_retries:
+                    logging.warning(
+                        f"PostgreSQL connection issue (attempt {attempt+1}/{self.max_retries}): {e}"
+                    )
+                    self._handle_connection_loss()
+                    time.sleep(self.retry_delay * (2 ** attempt))
+                else:
+                    logging.error(f"PostgreSQL execution failure: {e}")
+                    raise
+        return None
+
+    def _handle_connection_loss(self):
+        try:
+            self.close()
+        except Exception:
+            pass
+        try:
+            self.connect()
+        except Exception as e:
+            logging.error(f"Failed to reconnect to PostgreSQL: {e}")
+            time.sleep(0.1)
+            self.connect()
+
+    def begin(self):
+        for attempt in range(self.max_retries + 1):
+            try:
+                return super().begin()
+            except (OperationalError, InterfaceError) as e:
+                error_messages = ['connection', 'server closed', 'connection refused',
+                                'no connection to the server', 'terminating connection']
+                
+                should_retry = any(msg in str(e).lower() for msg in error_messages)
+
+                if should_retry and attempt < self.max_retries:
+                    logging.warning(
+                        f"PostgreSQL connection lost during transaction (attempt {attempt+1}/{self.max_retries})"
+                    )
+                    self._handle_connection_loss()
+                    time.sleep(self.retry_delay * (2 ** attempt))
+                else:
+                    raise
+
+
 class PooledDatabase(Enum):
     MYSQL = RetryingPooledMySQLDatabase
-    POSTGRES = PooledPostgresqlDatabase
+    POSTGRES = RetryingPooledPostgresqlDatabase
 
 
 class DatabaseMigrator(Enum):