# ClickHouse Database Connection Guide

## Connection Details
- **Host**: localhost
- **Port**: 9000 (HTTP), 9004 (HTTPS), 9009 (Native TCP)
- **Protocol**: HTTP/TCP (ClickHouse native)
- **Default Database**: default
- **Health Check**: `clickhouse-client --query "SELECT version()"`

## Authentication
- **Default User**: default (no password)
- **Access**: Localhost only, no authentication required
- **Security**: Development mode - add authentication for production

## ClickHouse-CLI Examples
```bash
# Connect to ClickHouse
clickhouse-client

# Show databases
SHOW DATABASES;

# Create nova database
CREATE DATABASE nova_analytics;

# Basic query
SELECT version(), now(), currentDatabase();

# Table operations
CREATE TABLE nova_analytics.events (
    timestamp DateTime,
    event_type String,
    data String
) ENGINE = MergeTree()
ORDER BY timestamp;

INSERT INTO nova_analytics.events VALUES 
(now(), 'session_start', '{"user": "test"}');

SELECT * FROM nova_analytics.events;
```

## HTTP API Examples
```bash
# Health check via HTTP
curl "http://localhost:8123/?query=SELECT%20version()"

# Create table via HTTP
curl -X POST "http://localhost:8123/?query=CREATE%20TABLE%20test%20(id%20UInt32)%20ENGINE%20%3D%20Memory"

# Insert data
curl -X POST "http://localhost:8123/?query=INSERT%20INTO%20test%20VALUES%20(1)%2C%20(2)%2C%20(3)"

# Query data
curl "http://localhost:8123/?query=SELECT%20*%20FROM%20test"
```

## Python Client Example
```python
from clickhouse_driver import Client

# Connect to ClickHouse
client = Client(
    host='localhost',
    port=9000,
    user='default',
    database='default'
)

# Execute queries
version = client.execute('SELECT version()')
print(f"ClickHouse version: {version[0][0]}")

# Create analytics table
client.execute('''
CREATE TABLE IF NOT EXISTS nova_analytics.metrics (
    timestamp DateTime,
    metric_name String,
    value Float64,
    tags String
) ENGINE = MergeTree()
ORDER BY (metric_name, timestamp)
''')

# Insert metrics data
client.execute('''
INSERT INTO nova_analytics.metrics VALUES
(now(), 'memory_usage', 75.5, '{"host": "vast1"}'),
(now(), 'cpu_usage', 45.2, '{"host": "vast1"}')
''')

# Query analytics
results = client.execute('''
SELECT 
    metric_name,
    avg(value) as avg_value,
    max(timestamp) as last_seen
FROM nova_analytics.metrics 
GROUP BY metric_name
''')

for row in results:
    print(f"Metric: {row[0]}, Avg: {row[1]:.2f}, Last: {row[2]}")
```

## Configuration Notes
- **Data Directory**: `/data/data/clickhouse/data/`
- **Log Directory**: `/data/data/clickhouse/logs/`
- **Max Memory**: 50GB (configurable)
- **Backup Location**: `/data/adaptai/backups/clickhouse/`
- **Port Configuration**: 
  - 8123: HTTP interface
  - 9000: Native TCP interface
  - 9004: HTTPS interface
  - 9009: Native TCP with SSL

## Performance Tuning
```sql
-- Monitor system metrics
SELECT * FROM system.metrics LIMIT 10;

-- Check query performance
SELECT 
    query,
    elapsed,
    read_rows,
    memory_usage
FROM system.processes;

-- Table sizes and parts
SELECT 
    database,
    table,
    sum(bytes) as size_bytes
FROM system.parts 
GROUP BY database, table
ORDER BY size_bytes DESC;
```

## Health Checks
```bash
# Basic connectivity
clickhouse-client --query "SELECT 1"

# System health
clickhouse-client --query "SELECT * FROM system.metrics WHERE metric LIKE '%memory%'"

# Disk usage
clickhouse-client --query "
SELECT 
    name,
    free_space,
    total_space,
    formatReadableSize(free_space) as free,
    formatReadableSize(total_space) as total
FROM system.disks
"

# Active queries
clickhouse-client --query "SELECT query, elapsed FROM system.processes"
```

## Security
- ❗ Localhost binding only
- ❗ No authentication configured (development mode)
- ❗ Add password authentication for production
- ❗ Monitor disk usage on /data partition
- ❗ Regular backups recommended
- ❗ Consider enabling SSL for encrypted connections

## Backup Procedures
```bash
# Create backup
clickhouse-client --query "BACKUP DATABASE nova_analytics TO '/data/adaptai/backups/clickhouse/nova_analytics_backup'"

# Restore backup
clickhouse-client --query "RESTORE DATABASE nova_analytics FROM '/data/adaptai/backups/clickhouse/nova_analytics_backup'"

# Manual file backup
sudo rsync -av /data/data/clickhouse/data/ /data/adaptai/backups/clickhouse/full_backup/
```

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**Last Updated:** September 4, 2025