> ## Documentation Index
> Fetch the complete documentation index at: https://private-7c7dfe99-mintlify-8a08bda2.mintlify.site/llms.txt
> Use this file to discover all available pages before exploring further.

# DataStore logging

> Configure DataStore logging for debugging and monitoring

DataStore uses Python's standard logging module. This guide shows how to configure logging for debugging.

<h2 id="quick-start">
  Quick Start
</h2>

```python theme={null}
from pathlib import Path
Path("data.csv").write_text("""\
name,age,city,salary,department
Alice,25,NYC,55000,Engineering
Bob,30,LA,65000,Product
Charlie,35,NYC,80000,Engineering
Diana,28,SF,70000,Design
Eve,42,NYC,95000,Product
""")

from chdb import datastore as pd
from chdb.datastore.config import config

# Enable debug logging
config.enable_debug()

# Now all operations will log details
ds = pd.read_csv("data.csv")
result = ds.filter(ds['age'] > 25).to_df()
```

<h2 id="levels">
  Log Levels
</h2>

| Level      | Value | Description                        |
| ---------- | ----- | ---------------------------------- |
| `DEBUG`    | 10    | Detailed information for debugging |
| `INFO`     | 20    | General operational information    |
| `WARNING`  | 30    | Warning messages (default)         |
| `ERROR`    | 40    | Error messages                     |
| `CRITICAL` | 50    | Critical failures                  |

<h2 id="setting-level">
  Setting Log Level
</h2>

```python theme={null}
import logging
from chdb.datastore.config import config

# Using standard logging levels
config.set_log_level(logging.DEBUG)
config.set_log_level(logging.INFO)
config.set_log_level(logging.WARNING)  # Default
config.set_log_level(logging.ERROR)

# Using quick preset
config.enable_debug()  # Sets DEBUG level + verbose format
```

<h2 id="format">
  Log Format
</h2>

<h3 id="simple">
  Simple Format (Default)
</h3>

```python title="Query" theme={null}
config.set_log_format("simple")
```

```text title="Response" theme={null}
DEBUG - Executing SQL query
DEBUG - Cache miss for key abc123
```

<h3 id="verbose">
  Verbose Format
</h3>

```python title="Query" theme={null}
config.set_log_format("verbose")
```

```text title="Response" theme={null}
2024-01-15 10:30:45.123 DEBUG datastore.core - Executing SQL query
2024-01-15 10:30:45.456 DEBUG datastore.cache - Cache miss for key abc123
```

***

<h2 id="what-logged">
  What Gets Logged
</h2>

<h3 id="debug-logged">
  DEBUG Level
</h3>

* SQL queries generated
* Execution engine selection
* Cache operations (hits/misses)
* Operation timings
* Data source information

```text theme={null}
DEBUG - Creating DataStore from file 'data.csv'
DEBUG - SQL: SELECT * FROM file('data.csv', 'CSVWithNames') WHERE age > 25
DEBUG - Using engine: chdb
DEBUG - Execution time: 0.089s
DEBUG - Cache: Storing result (key: abc123)
```

<h3 id="info-logged">
  INFO Level
</h3>

* Major operation completions
* Configuration changes
* Data source connections

```text theme={null}
INFO - Loaded 1,000,000 rows from data.csv
INFO - Execution engine set to: chdb
INFO - Connected to MySQL: localhost:3306/mydb
```

<h3 id="warning-logged">
  WARNING Level
</h3>

* Deprecated feature usage
* Performance warnings
* Non-critical issues

```text theme={null}
WARNING - Large result set (>1M rows) may cause memory issues
WARNING - Cache TTL exceeded, re-executing query
WARNING - Column 'date' has mixed types, using string
```

<h3 id="error-logged">
  ERROR Level
</h3>

* Query execution failures
* Connection errors
* Data conversion errors

```text theme={null}
ERROR - Failed to execute SQL: syntax error near 'FORM'
ERROR - Connection to MySQL failed: timeout
ERROR - Cannot convert column 'price' to float
```

***

<h2 id="custom">
  Custom Logging Configuration
</h2>

<h3 id="python-logging">
  Using Python Logging
</h3>

```python theme={null}
import logging

# Configure root logger
logging.basicConfig(
    level=logging.DEBUG,
    format='%(asctime)s - %(name)s - %(levelname)s - %(message)s',
    handlers=[
        logging.FileHandler('datastore.log'),
        logging.StreamHandler()
    ]
)

# Get DataStore logger
ds_logger = logging.getLogger('chdb.datastore')
ds_logger.setLevel(logging.DEBUG)
```

<h3 id="log-file">
  Log to File
</h3>

```python theme={null}
import logging

# Create file handler
file_handler = logging.FileHandler('datastore_debug.log')
file_handler.setLevel(logging.DEBUG)
file_handler.setFormatter(logging.Formatter(
    '%(asctime)s - %(name)s - %(levelname)s - %(message)s'
))

# Add to DataStore logger
ds_logger = logging.getLogger('chdb.datastore')
ds_logger.addHandler(file_handler)
```

<h3 id="suppress">
  Suppress Logging
</h3>

```python theme={null}
import logging

# Suppress all DataStore logs
logging.getLogger('chdb.datastore').setLevel(logging.CRITICAL)

# Or using config
config.set_log_level(logging.CRITICAL)
```

***

<h2 id="scenarios">
  Debugging Scenarios
</h2>

<h3 id="debug-sql">
  Debug SQL Generation
</h3>

```python theme={null}
config.enable_debug()

ds = pd.read_csv("data.csv")
result = ds.filter(ds['age'] > 25).groupby('city').sum()
```

Log output:

```text theme={null}
DEBUG - Creating DataStore from file 'data.csv'
DEBUG - Building filter: age > 25
DEBUG - Building groupby: city
DEBUG - Building aggregation: sum
DEBUG - Generated SQL:
        SELECT city, SUM(*) 
        FROM file('data.csv', 'CSVWithNames')
        WHERE age > 25
        GROUP BY city
```

<h3 id="debug-engine">
  Debug Engine Selection
</h3>

```python theme={null}
config.enable_debug()

result = ds.filter(ds['x'] > 10).apply(custom_func)
```

Log output:

```text theme={null}
DEBUG - filter: selecting engine (eligible: chdb, pandas)
DEBUG - filter: using chdb (SQL-compatible)
DEBUG - apply: selecting engine (eligible: pandas)
DEBUG - apply: using pandas (custom function)
```

<h3 id="debug-cache">
  Debug Cache Operations
</h3>

```python theme={null}
config.enable_debug()

# First execution
result1 = ds.filter(ds['age'] > 25).to_df()
# DEBUG - Cache miss for query hash abc123
# DEBUG - Executing query...
# DEBUG - Caching result (key: abc123, size: 1.2MB)

# Second execution (same query)
result2 = ds.filter(ds['age'] > 25).to_df()
# DEBUG - Cache hit for query hash abc123
# DEBUG - Returning cached result
```

<h3 id="debug-performance">
  Debug Performance Issues
</h3>

```python theme={null}
config.enable_debug()
config.enable_profiling()

# Logs will show timing for each operation
result = (ds
    .filter(ds['amount'] > 100)
    .groupby('region')
    .agg({'amount': 'sum'})
    .to_df()
)
```

Log output:

```text theme={null}
DEBUG - filter: 0.002ms
DEBUG - groupby: 0.001ms
DEBUG - agg: 0.003ms
DEBUG - SQL generation: 0.012ms
DEBUG - SQL execution: 89.456ms  <- Main time spent here
DEBUG - Result conversion: 2.345ms
```

***

<h2 id="production">
  Production Configuration
</h2>

<h3 id="recommended">
  Recommended Settings
</h3>

```python theme={null}
import logging
from chdb.datastore.config import config

# Production: minimal logging
config.set_log_level(logging.WARNING)
config.set_log_format("simple")
config.set_profiling_enabled(False)
```

<h3 id="rotation">
  Log Rotation
</h3>

```python theme={null}
import logging
from logging.handlers import RotatingFileHandler

# Create rotating file handler
handler = RotatingFileHandler(
    'datastore.log',
    maxBytes=10*1024*1024,  # 10MB
    backupCount=5
)
handler.setLevel(logging.WARNING)

# Add to DataStore logger
logging.getLogger('chdb.datastore').addHandler(handler)
```

***

<h2 id="env-vars">
  Environment Variables
</h2>

You can also configure logging via environment variables:

```bash theme={null}
# Set log level
export CHDB_LOG_LEVEL=DEBUG

# Set log format
export CHDB_LOG_FORMAT=verbose
```

```python theme={null}
import os
import logging

# Read from environment
log_level = os.environ.get('CHDB_LOG_LEVEL', 'WARNING')
config.set_log_level(getattr(logging, log_level))
```

***

<h2 id="summary">
  Summary
</h2>

| Task          | Command                                  |
| ------------- | ---------------------------------------- |
| Enable debug  | `config.enable_debug()`                  |
| Set level     | `config.set_log_level(logging.DEBUG)`    |
| Set format    | `config.set_log_format("verbose")`       |
| Log to file   | Use Python logging handlers              |
| Suppress logs | `config.set_log_level(logging.CRITICAL)` |