# PostgreSQL Plugin Refactoring Summary

## Overview
Refactored `noetl/plugin/postgres.py` (498 lines) into a modular package structure with clear separation of concerns: authentication, command parsing, SQL execution, response processing, and task orchestration.

## Previous Structure (Monolithic)

```
noetl/plugin/
└── postgres.py      # Single file with all PostgreSQL logic (498 lines)
```

**Problems**:
- Mixed concerns (auth, parsing, execution, response)
- Long single file difficult to navigate
- Complex SQL parsing logic embedded in main function
- Tightly coupled logic
- Hard to test individual components

## New Structure (Modular Package)

```
noetl/plugin/postgres/
├── __init__.py      (31 lines)  - Package exports
├── auth.py          (224 lines) - Authentication & connection params
├── command.py       (178 lines) - Command parsing & SQL splitting
├── execution.py     (180 lines) - SQL execution & transaction handling
├── response.py      (100 lines) - Response processing & formatting
└── executor.py      (174 lines) - Main orchestration logic
```

**Total**: 887 lines (increase of 389 lines / 78% due to enhanced documentation and structure)

## Module Breakdown

### 1. **auth.py** (224 lines)

**Purpose**: Handle authentication resolution and connection parameter validation

**Functions**:
- `resolve_postgres_auth()`: Resolve PostgreSQL authentication from unified auth or legacy credentials
- `validate_and_render_connection_params()`: Validate and render connection parameters with Jinja2

**Supported Auth Sources**:
- **Unified Auth System**: Modern auth configuration with service-specific payload
- **Legacy Credentials**: Backward compatible credential reference
- **Direct Parameters**: Explicit db_* fields in task `with` parameters

**Field Mapping**:
```python
# Supports multiple field name variations
'host' / 'db_host' / 'pg_host' → db_host
'port' / 'db_port' → db_port
'user' / 'username' / 'db_user' → db_user
'password' / 'db_password' → db_password
'database' / 'dbname' / 'db_name' → db_name
'dsn' / 'connection_string' → db_conn_string
```

**Features**:
- Automatic parameter mapping from auth payload
- Connection string building or validation
- Jinja2 template rendering for dynamic values
- Comprehensive validation with clear error messages
- Backward compatibility with legacy credential system

### 2. **command.py** (178 lines)

**Purpose**: Parse, decode, and split SQL commands

**Functions**:
- `escape_task_with_params()`: Escape special characters for SQL compatibility
- `decode_base64_commands()`: Decode base64 encoded SQL commands
- `render_and_split_commands()`: Render Jinja2 templates and split into statements

**Features**:
- **Base64 Decoding**: Supports `command_b64` and `commands_b64` fields
- **Jinja2 Rendering**: Full template support with context and task_with variables
- **Comment Removal**: Strips SQL comments (-- style) before execution
- **Quote-Aware Splitting**: Intelligent statement splitting that respects:
  - Single quotes (`'...'`)
  - Double quotes (`"..."`)
  - Dollar-quoted strings (`$tag$...$tag$`)
- **SQL Injection Protection**: Character escaping for task parameters

**Example**:
```sql
-- This comment is removed
SELECT * FROM users WHERE id = {{ user_id }};
INSERT INTO logs VALUES ($body$Complex 'text' with "quotes"$body$);
```

### 3. **execution.py** (180 lines)

**Purpose**: Execute SQL statements with proper transaction handling

**Functions**:
- `connect_to_postgres()`: Establish database connection with error handling
- `execute_sql_statements()`: Execute multiple SQL statements with result collection
- `_fetch_result_rows()`: Format result rows with type conversion

**Features**:
- **Transaction Management**: Automatic transaction wrapping for statements
- **CALL Statement Support**: Special handling with autocommit mode
- **Result Data Extraction**: Automatic for SELECT and RETURNING clauses
- **Type Conversion**: 
  - Decimal → float (JSON serializable)
  - JSON/dict → preserve as-is
- **Error Handling**: Per-statement error capture without stopping execution
- **Password Redaction**: Safe logging without exposing credentials

**Execution Modes**:
- **Regular Statements** (SELECT, INSERT, UPDATE, DELETE, DDL): Use transaction
- **CALL Statements** (Stored Procedures): Use autocommit mode

### 4. **response.py** (100 lines)

**Purpose**: Process execution results and format responses

**Functions**:
- `process_results()`: Check for errors and aggregate error messages
- `format_success_response()`: Format successful task response
- `format_error_response()`: Format error task response
- `format_exception_response()`: Format exception response with traceback

**Response Formats**:

**Success**:
```python
{
    'id': 'task-uuid',
    'status': 'success',
    'data': {
        'command_0': {
            'status': 'success',
            'rows': [...],
            'row_count': 5,
            'columns': ['id', 'name']
        }
    }
}
```

**Error**:
```python
{
    'id': 'task-uuid',
    'status': 'error',
    'error': 'command_0: syntax error; ',
    'data': {...}  # Partial results
}
```

**Exception**:
```python
{
    'id': 'task-uuid',
    'status': 'error',
    'error': 'Connection failed',
    'traceback': '...'
}
```

### 5. **executor.py** (174 lines)

**Purpose**: Main orchestration and task lifecycle management

**Main Function**:
- `execute_postgres_task()`: Primary entry point for PostgreSQL task execution

**Execution Flow**:
1. **Authentication**: Resolve auth and connection parameters
2. **Validation**: Validate required parameters
3. **Command Processing**: Decode, escape, render, and split SQL
4. **Event Logging**: Log task_start event
5. **Connection**: Establish database connection
6. **Execution**: Execute all SQL statements
7. **Cleanup**: Close connection
8. **Result Processing**: Check for errors
9. **Event Logging**: Log task_complete or task_error
10. **Error Logging**: Log to error database if needed
11. **Response**: Return formatted result

**Features**:
- Comprehensive error handling at each step
- Event callback integration for monitoring
- Database error logging
- Detailed execution tracing
- Backward compatibility preservation

## Key Features

### Authentication Support

**Unified Auth System**:
```python
auth_config = {
    'type': 'postgres',
    'host': 'localhost',
    'port': 5432,
    'user': 'myuser',
    'password': 'secret',
    'database': 'mydb'
}
```

**Legacy Credential Reference**:
```python
task_with = {
    'credential': 'postgres_prod'
}
```

**Direct Parameters**:
```python
task_with = {
    'db_host': 'localhost',
    'db_port': '5432',
    'db_user': 'user',
    'db_password': 'pass',
    'db_name': 'database'
}
```

### SQL Command Execution

**Base64 Encoding**:
```python
import base64
sql = "SELECT * FROM users;"
task_config = {
    'command_b64': base64.b64encode(sql.encode()).decode()
}
```

**Multi-Statement Support**:
```python
sql = """
SELECT * FROM users;
INSERT INTO logs (message) VALUES ('Action performed');
CALL update_stats();
"""
```

**Jinja2 Templates**:
```python
sql = """
SELECT * FROM {{ table_name }}
WHERE created_at > '{{ start_date }}'
  AND status = '{{ status }}';
"""
```

### Transaction Handling

**Automatic Transactions**:
- Regular statements execute within transactions
- Automatic rollback on error
- Commit on success

**Stored Procedures**:
- CALL statements use autocommit mode
- Required for procedures with transaction control

## Usage

```python
from noetl.plugin.postgres import execute_postgres_task
from jinja2 import Environment
import base64

# Prepare SQL commands
sql = "SELECT * FROM users WHERE id = {{ user_id }};"
encoded_sql = base64.b64encode(sql.encode()).decode()

# Execute task
result = execute_postgres_task(
    task_config={
        'command_b64': encoded_sql,
        'task': 'fetch_users'
    },
    context={
        'execution_id': 'exec-123',
        'user_id': 42
    },
    jinja_env=Environment(),
    task_with={
        'db_host': 'localhost',
        'db_port': '5432',
        'db_user': 'myuser',
        'db_password': 'mypass',
        'db_name': 'mydb'
    },
    log_event_callback=my_logger
)

print(result['status'])  # 'success'
print(result['data'])    # Query results
```

## Migration Path

### Before
```python
from noetl.plugin.postgres import execute_postgres_task
```

### After (No Change)
```python
# Same import works - fully backward compatible
from noetl.plugin.postgres import execute_postgres_task
from noetl.plugin import execute_postgres_task
```

## Changes Made

1. **Created postgres package**: Split monolithic file into 5 focused modules
2. **Separated concerns**:
   - Authentication & validation → `auth.py`
   - Command parsing & splitting → `command.py`
   - SQL execution → `execution.py`
   - Response formatting → `response.py`
   - Task orchestration → `executor.py`
3. **Enhanced modularity**: Each module can be tested independently
4. **Improved documentation**: Comprehensive docstrings with examples
5. **Maintained API**: Zero breaking changes - same public interface

## Files Modified

**Created**:
- `noetl/plugin/postgres/__init__.py`
- `noetl/plugin/postgres/auth.py`
- `noetl/plugin/postgres/command.py`
- `noetl/plugin/postgres/execution.py`
- `noetl/plugin/postgres/response.py`
- `noetl/plugin/postgres/executor.py`

**Removed**:
- `noetl/plugin/postgres.py`

**No Other Changes**: All other code continues to work without modification

## Benefits

### 1. **Clear Separation of Concerns**
- Authentication isolated from execution
- Command parsing separate from SQL execution
- Response formatting independent module
- Each module has single responsibility

### 2. **Improved Testability**
- Test auth resolution independently
- Test SQL parsing without database
- Test execution with mock connections
- Test response formatting with sample data
- Mock dependencies easily

### 3. **Better Maintainability**
- Smaller, focused modules easier to understand
- Changes isolated to relevant module
- Reduced risk of unintended side effects
- Clear module boundaries

### 4. **Enhanced Readability**
- Clear module names indicate purpose
- Well-documented functions with examples
- Logical code organization
- Step-by-step execution flow

### 5. **Easier Extension**
- Add new auth sources to `auth.py`
- Add command formats to `command.py`
- Add execution modes to `execution.py`
- Add response formats to `response.py`
- No need to modify unrelated code

### 6. **100% Backward Compatible**
- Same public API
- Same function signature
- Same behavior
- No breaking changes

## Line Count Analysis

**Before**: 498 lines (single file)

**After**: 887 lines (6 files)
- `__init__.py`: 31 lines
- `auth.py`: 224 lines
- `command.py`: 178 lines
- `execution.py`: 180 lines
- `response.py`: 100 lines
- `executor.py`: 174 lines

**Increase**: 389 lines (78% increase)

**Reasons for increase**:
- Enhanced documentation (detailed docstrings with examples)
- Better code structure (helper functions)
- Improved separation (less coupling)
- Package initialization and exports
- More descriptive logging
- Comprehensive error handling
- Example usage in docstrings

## Verification

✅ All imports work correctly
✅ execute_postgres_task function signature maintained
✅ All sub-modules load properly
✅ Server loads successfully (85 routes)
✅ Worker module functional
✅ Old postgres.py file removed
✅ Zero breaking changes

## Design Philosophy

### Separation of Concerns
Each module handles one aspect:
- **auth**: Authentication and connection management
- **command**: Command parsing and SQL splitting
- **execution**: Database operations and transaction handling
- **response**: Result processing and formatting
- **executor**: Task lifecycle orchestration

### Single Responsibility
Each function does one thing well:
- `resolve_postgres_auth`: Only resolves authentication
- `decode_base64_commands`: Only decodes commands
- `execute_sql_statements`: Only executes SQL
- `format_success_response`: Only formats success responses
- `execute_postgres_task`: Only orchestrates execution flow

### Composability
Modules work together through well-defined interfaces:
```
executor.py
    ↓ uses
auth.py → resolve_postgres_auth() → validate_and_render_connection_params()
command.py → decode_base64_commands() → render_and_split_commands()
execution.py → connect_to_postgres() → execute_sql_statements()
response.py → process_results() → format_*_response()
```

### Testability
Each module can be tested independently:
- Mock auth resolution in `auth.py` tests
- Mock database in `execution.py` tests
- Test parsing without execution
- Test formatting with sample data
- Integration tests in `executor.py`

## Advanced Features

### Quote-Aware SQL Splitting
The command parser correctly handles:
```sql
-- Single quotes
SELECT * FROM users WHERE name = 'O''Brien';

-- Double quotes
SELECT * FROM "my table" WHERE "column-name" = 'value';

-- Dollar-quoted strings (PostgreSQL specific)
INSERT INTO docs VALUES ($tag$This 'text' has "quotes"$tag$);
```

### Transaction Control
Automatic transaction management:
- Regular statements use `with conn.transaction():`
- CALL statements use `conn.autocommit = True`
- Errors trigger rollback
- Success triggers commit

### Type Conversion
Automatic type handling for JSON serialization:
- `Decimal` → `float`
- `dict` → preserved
- JSON strings → preserved
- Other types → preserved

### Error Recovery
Per-statement error handling:
- Statement errors don't stop execution
- Partial results returned
- Error messages aggregated
- Overall status reflects any errors

This refactoring transforms the PostgreSQL plugin into a maintainable, testable, and extensible package while maintaining 100% backward compatibility!
