Database Tools

Overview

The vCon MCP server provides three powerful tools for database debugging, performance monitoring, and optimization.

Available Tools

1. get_database_shape - Database Structure Inspector

Get comprehensive information about your database structure including tables, indexes, sizes, and relationships.

Use Cases:

• Understanding database schema

• Checking table and index sizes

• Identifying relationships between tables

• Database documentation

Parameters:

{
  "include_counts": true,    // Include row counts (default: true)
  "include_sizes": true,     // Include disk sizes (default: true)
  "include_indexes": true,   // Include index info (default: true)
  "include_columns": false   // Include column details (default: false)
}

Example Request:

{
  "tool": "get_database_shape",
  "arguments": {
    "include_counts": true,
    "include_sizes": true,
    "include_indexes": true,
    "include_columns": false
  }
}

Example Response:

{
  "success": true,
  "database_shape": {
    "timestamp": "2024-10-14T12:00:00Z",
    "tables": [
      {
        "name": "vcons",
        "schema": "public",
        "row_count": 4443,
        "total_size": "1024 kB",
        "table_size": "896 kB",
        "indexes_size": "128 kB",
        "indexes": [
          {
            "indexname": "vcons_pkey",
            "index_type": "btree",
            "index_size": "48 kB"
          },
          {
            "indexname": "idx_vcons_uuid",
            "index_type": "btree",
            "index_size": "40 kB"
          }
        ]
      }
    ],
    "relationships": [
      {
        "from_table": "dialog",
        "from_column": "vcon_id",
        "to_table": "vcons",
        "to_column": "id"
      }
    ]
  }
}

What You Get:

• ✅ Table names and schemas

• ✅ Row counts for each table

• ✅ Disk sizes (table + indexes)

• ✅ Index information (name, type, size)

• ✅ Column definitions (optional)

• ✅ Foreign key relationships

---

2. get_database_stats - Performance & Usage Statistics

Get detailed performance metrics, cache statistics, and table access patterns.

Use Cases:

• Performance monitoring

• Identifying hot tables

• Finding unused indexes

• Cache optimization

• Query pattern analysis

Parameters:

{
  "include_query_stats": true,   // Table access patterns (default: true)
  "include_index_usage": true,   // Index usage stats (default: true)
  "include_cache_stats": true,   // Cache hit ratios (default: true)
  "table_name": null             // Optional: specific table
}

Example Request:

{
  "tool": "get_database_stats",
  "arguments": {
    "include_query_stats": true,
    "include_index_usage": true,
    "include_cache_stats": true
  }
}

Example Response:

{
  "success": true,
  "database_stats": {
    "timestamp": "2024-10-14T12:00:00Z",
    "cache_stats": {
      "hit_ratio": "0.9850",
      "heap_blocks_hit": 123456,
      "heap_blocks_read": 1876
    },
    "table_stats": [
      {
        "table_name": "vcons",
        "sequential_scans": 45,
        "sequential_rows_read": 199935,
        "index_scans": 8934,
        "index_rows_fetched": 12456,
        "inserts": 4443,
        "updates": 234,
        "deletes": 12,
        "live_rows": 4431,
        "dead_rows": 15
      }
    ],
    "index_usage": [
      {
        "table_name": "vcons",
        "index_name": "idx_vcons_uuid",
        "scans": 8934,
        "rows_read": 8934,
        "rows_fetched": 8934
      }
    ],
    "unused_indexes": [
      {
        "table_name": "old_table",
        "index_name": "idx_old_field",
        "index_size": "24 MB"
      }
    ]
  }
}

What You Get:

Cache Statistics

• Hit Ratio: Percentage of reads served from cache (higher is better)

• Blocks Hit: Number of times data was found in cache

• Blocks Read: Number of times data had to be read from disk

Recommended Action:

• Hit ratio < 90%: Consider increasing shared_buffers

• Hit ratio > 99%: Cache is well-tuned

Table Access Patterns

• Sequential Scans: Full table scans (may indicate missing indexes)

• Index Scans: Index-based access (efficient)

• Modifications: Inserts, updates, deletes

• Dead Rows: Rows marked for deletion (may need VACUUM)

Recommended Actions:

• High sequential scans on large tables: Add indexes

• Many dead rows: Run VACUUM ANALYZE

• Low index usage: Index might not be optimal

Index Usage

• Scans: How many times the index was used

• Rows Fetched: How many rows were accessed via index

Recommended Actions:

• Scans = 0: Index is unused, consider dropping

• Many scans: Index is valuable, keep it

Unused Indexes

Lists indexes that have never been used since stats reset.

Recommended Actions:

• Drop unused indexes to improve write performance

• Each index slows down INSERT/UPDATE/DELETE operations

• Keep only indexes that provide query benefits

---

3. analyze_query - Query Performance Analysis

Analyze SQL query execution plans to understand performance characteristics.

Note: This tool has limitations with the current database setup. The exec_sql RPC may not support EXPLAIN statements. For full query analysis, use direct database access.

Use Cases:

• Understanding query performance

• Identifying slow queries

• Optimizing index usage

• Planning query improvements

Parameters:

{
  "query": "SELECT ...",          // SQL query to analyze
  "analyze_mode": "explain"       // "explain" or "explain_analyze"
}

Modes:

• explain: Generate execution plan without running query (fast, safe)

• explain_analyze: Run query and measure actual performance (slower, provides real metrics)

Limitations:

• Only SELECT queries are allowed (for safety)

• May not work with all database configurations

• Requires exec_sql RPC support for EXPLAIN

Alternative Approach: If this tool doesn't work in your environment, you can:

1. Connect directly to the database with psql

2. Run EXPLAIN (ANALYZE, BUFFERS) your_query;

3. Analyze the output manually

---

Common Use Cases

1. Database Health Check

# Get complete database overview
Tool: get_database_shape
Arguments: { "include_counts": true, "include_sizes": true }

# Check performance metrics
Tool: get_database_stats
Arguments: { "include_cache_stats": true }

Look for:

• Large table sizes (may need partitioning)

• Many dead rows (run VACUUM)

• Low cache hit ratio (tune memory)

2. Performance Optimization

# Find unused indexes
Tool: get_database_stats
Arguments: { "include_index_usage": true }

# Check table access patterns
Tool: get_database_stats
Arguments: { "include_query_stats": true }

Actions:

• Drop unused indexes

• Add indexes for high sequential scan tables

• Monitor index vs sequential scan ratios

3. Growth Monitoring

# Track table sizes over time
Tool: get_database_shape
Arguments: { "include_sizes": true, "include_counts": true }

Monitor:

• Row count growth

• Disk space usage

• Index size growth

4. Index Optimization

# Get all index information
Tool: get_database_shape
Arguments: { "include_indexes": true, "include_sizes": true }

# Check which indexes are being used
Tool: get_database_stats
Arguments: { "include_index_usage": true }

Strategy:

• Drop unused indexes (0 scans)

• Consolidate overlapping indexes

• Add indexes for frequently scanned tables

---

Performance Metrics Interpretation

Cache Hit Ratio

Ratio	Status	Action
> 99%	Excellent	No action needed
95-99%	Good	Monitor
90-95%	Fair	Consider increasing shared_buffers
< 90%	Poor	Increase shared_buffers, check queries

Sequential vs Index Scans

Scenario	Interpretation	Action
High seq scans, small table	OK	Small tables are fine to scan
High seq scans, large table	Problem	Add index
High index scans	Good	Indexes working well
Low scans overall	Variable	Check if table is actively used

Dead Rows

Dead Rows	Action
< 5% of live rows	OK
5-20%	Schedule VACUUM
> 20%	Run VACUUM immediately

---

Best Practices

1. Regular Health Checks

Run these tools:

• Daily: get_database_stats (cache, hot tables)

• Weekly: get_database_shape (sizes, growth)

• Monthly: Full analysis (unused indexes, optimization opportunities)

2. Performance Tuning Workflow

1. Identify slow areas using get_database_stats

2. Analyze specific queries (if supported)

3. Optimize by adding/dropping indexes

4. Monitor improvements with stats

3. Index Management

When to add an index:

• High sequential scans on large table

• Frequent WHERE/JOIN conditions on column

• Slow queries using that column

When to drop an index:

• 0 scans in index_usage

• Overlaps with another index

• Table is write-heavy and read-light

4. Maintenance Schedule

Based on database stats:

• VACUUM: When dead rows > 10%

• ANALYZE: After large data changes

• REINDEX: If index bloat suspected

---

Example Workflow: Finding and Fixing Performance Issues

Step 1: Check Overall Health

{
  "tool": "get_database_stats",
  "arguments": {
    "include_cache_stats": true,
    "include_query_stats": true
  }
}

Step 2: Identify Problem Tables

Look for:

• Tables with high sequential scans

• Tables with many dead rows

• Low cache hit ratios

Step 3: Check Indexes

{
  "tool": "get_database_shape",
  "arguments": {
    "include_indexes": true
  }
}

Step 4: Review Index Usage

{
  "tool": "get_database_stats",
  "arguments": {
    "include_index_usage": true,
    "table_name": "problematic_table"
  }
}

Step 5: Take Action

• Add missing indexes

• Drop unused indexes

• Run VACUUM on tables with dead rows

• Tune cache settings if needed

---

Test Script

Run the test script to see all tools in action:

npx tsx scripts/test-database-tools.ts

This will:

• Show database structure

• Display performance metrics

• Identify optimization opportunities

• Demonstrate all available features

---

Troubleshooting

"Permission denied" errors

• Ensure you're using SUPABASE_SERVICE_ROLE_KEY (not anon key)

• Check that exec_sql RPC has proper permissions

"Function not found" errors

• Ensure migrations are applied: supabase db reset

• Check that exec_sql RPC exists in your database

Slow performance

• Run with smaller scope (single table)

• Disable expensive options (include_columns, include_sizes)

• Use table_name parameter to focus on specific tables

---

Related Documentation

• Database Migrations - Database schema

• SUPABASE_SEMANTIC_SEARCH_GUIDE.md - Search performance

• INGEST_AND_EMBEDDINGS.md - Data ingestion

---

Summary

The database inspection tools provide comprehensive visibility into your vCon database:

1. get_database_shape - Structure, sizes, relationships

2. get_database_stats - Performance, usage, optimization opportunities

3. analyze_query - Query execution analysis (limited support)

Use these tools to:

• Monitor database health

• Optimize performance

• Identify bottlenecks

• Plan capacity

• Debug issues

Regular use of these tools will help maintain a healthy, performant database.