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Create Database Migrations

Create and manage database migrations

Instructions

  1. Migration Strategy and Planning

    • Analyze current database schema and target changes
    • Plan migration strategy for zero-downtime deployments
    • Define rollback procedures and data safety measures
    • Assess migration complexity and potential risks
    • Plan for data transformation and validation

  2. Migration Framework Setup

    • Set up comprehensive migration framework:

    Node.js Migration Framework:

    // migrations/migration-framework.js
const fs = require('fs').promises;
const path = require('path');
const { Pool } = require('pg');

class MigrationManager {
  constructor(databaseConfig) {
    this.pool = new Pool(databaseConfig);
    this.migrationsDir = path.join(__dirname, 'migrations');
    this.lockTimeout = 30000; // 30 seconds
  }

  async initialize() {
    // Create migrations tracking table
    await this.pool.query(`
      CREATE TABLE IF NOT EXISTS schema_migrations (
        id SERIAL PRIMARY KEY,
        version VARCHAR(255) UNIQUE NOT NULL,
        name VARCHAR(255) NOT NULL,
        executed_at TIMESTAMP WITH TIME ZONE DEFAULT CURRENT_TIMESTAMP,
        execution_time_ms INTEGER,
        checksum VARCHAR(64),
        rollback_sql TEXT,
        batch_number INTEGER
      );
      
      CREATE INDEX IF NOT EXISTS idx_schema_migrations_version 
      ON schema_migrations(version);
      
      CREATE INDEX IF NOT EXISTS idx_schema_migrations_batch 
      ON schema_migrations(batch_number);
    `);

    // Create migration lock table
    await this.pool.query(`
      CREATE TABLE IF NOT EXISTS migration_lock (
        id INTEGER PRIMARY KEY DEFAULT 1,
        is_locked BOOLEAN DEFAULT FALSE,
        locked_at TIMESTAMP WITH TIME ZONE,
        locked_by VARCHAR(255),
        CHECK (id = 1)
      );
      
      INSERT INTO migration_lock (id, is_locked) 
      VALUES (1, FALSE) 
      ON CONFLICT (id) DO NOTHING;
    `);
  }

  async acquireLock(lockId = 'migration') {
    const client = await this.pool.connect();
    try {
      const result = await client.query(`
        UPDATE migration_lock 
        SET is_locked = TRUE, locked_at = CURRENT_TIMESTAMP, locked_by = $1
        WHERE id = 1 AND (is_locked = FALSE OR locked_at < CURRENT_TIMESTAMP - INTERVAL '${this.lockTimeout} milliseconds')
        RETURNING is_locked;
      `, [lockId]);

      if (result.rows.length === 0) {
        throw new Error('Could not acquire migration lock - another migration may be running');
      }

      return client;
    } catch (error) {
      client.release();
      throw error;
    }
  }

  async releaseLock(client) {
    try {
      await client.query(`
        UPDATE migration_lock 
        SET is_locked = FALSE, locked_at = NULL, locked_by = NULL 
        WHERE id = 1;
      `);
    } finally {
      client.release();
    }
  }

  async getPendingMigrations() {
    const files = await fs.readdir(this.migrationsDir);
    const migrationFiles = files
      .filter(file => file.endsWith('.sql') || file.endsWith('.js'))
      .sort();

    const executedMigrations = await this.pool.query(
      'SELECT version FROM schema_migrations ORDER BY version'
    );
    const executedVersions = new Set(executedMigrations.rows.map(row => row.version));

    return migrationFiles
      .map(file => {
        const version = this.extractVersion(file);
        return { file, version, executed: executedVersions.has(version) };
      })
      .filter(migration => !migration.executed);
  }

  extractVersion(filename) {
    const match = filename.match(/^(\d{14})/);
    if (!match) {
      throw new Error(`Invalid migration filename format: ${filename}`);
    }
    return match[1];
  }

  async runMigration(migrationFile) {
    const version = this.extractVersion(migrationFile.file);
    const filePath = path.join(this.migrationsDir, migrationFile.file);
    const startTime = Date.now();

    console.log(`Running migration: ${migrationFile.file}`);

    const client = await this.pool.connect();
    try {
      await client.query('BEGIN');

      let migrationContent;
      let rollbackSql = '';

      if (migrationFile.file.endsWith('.js')) {
        // JavaScript migration
        const migration = require(filePath);
        await migration.up(client);
        rollbackSql = migration.down ? migration.down.toString() : '';
      } else {
        // SQL migration
        migrationContent = await fs.readFile(filePath, 'utf8');
        const { upSql, downSql } = this.parseSqlMigration(migrationContent);
        
        await client.query(upSql);
        rollbackSql = downSql;
      }

      const executionTime = Date.now() - startTime;
      const checksum = this.generateChecksum(migrationContent || migrationFile.file);
      const batchNumber = await this.getNextBatchNumber();

      // Record migration execution
      await client.query(`
        INSERT INTO schema_migrations (version, name, execution_time_ms, checksum, rollback_sql, batch_number)
        VALUES ($1, $2, $3, $4, $5, $6)
      `, [version, migrationFile.file, executionTime, checksum, rollbackSql, batchNumber]);

      await client.query('COMMIT');
      console.log(`✓ Migration ${migrationFile.file} completed in ${executionTime}ms`);

    } catch (error) {
      await client.query('ROLLBACK');
      console.error(`✗ Migration ${migrationFile.file} failed:`, error.message);
      throw error;
    } finally {
      client.release();
    }
  }

  parseSqlMigration(content) {
    const lines = content.split('\n');
    let upSql = '';
    let downSql = '';
    let currentSection = 'up';

    for (const line of lines) {
      if (line.trim().startsWith('-- +migrate Down')) {
        currentSection = 'down';
        continue;
      }
      if (line.trim().startsWith('-- +migrate Up')) {
        currentSection = 'up';
        continue;
      }

      if (currentSection === 'up') {
        upSql += line + '\n';
      } else if (currentSection === 'down') {
        downSql += line + '\n';
      }
    }

    return { upSql: upSql.trim(), downSql: downSql.trim() };
  }

  generateChecksum(content) {
    const crypto = require('crypto');
    return crypto.createHash('sha256').update(content).digest('hex');
  }

  async getNextBatchNumber() {
    const result = await this.pool.query(
      'SELECT COALESCE(MAX(batch_number), 0) + 1 as next_batch FROM schema_migrations'
    );
    return result.rows[0].next_batch;
  }

  async migrate() {
    await this.initialize();
    
    const client = await this.acquireLock('migration-runner');
    try {
      const pendingMigrations = await this.getPendingMigrations();
      
      if (pendingMigrations.length === 0) {
        console.log('No pending migrations');
        return;
      }

      console.log(`Found ${pendingMigrations.length} pending migrations`);
      
      for (const migration of pendingMigrations) {
        await this.runMigration(migration);
      }

      console.log('All migrations completed successfully');
    } finally {
      await this.releaseLock(client);
    }
  }

  async rollback(steps = 1) {
    await this.initialize();
    
    const client = await this.acquireLock('migration-rollback');
    try {
      const lastMigrations = await this.pool.query(`
        SELECT * FROM schema_migrations 
        ORDER BY executed_at DESC, version DESC 
        LIMIT $1
      `, [steps]);

      if (lastMigrations.rows.length === 0) {
        console.log('No migrations to rollback');
        return;
      }

      for (const migration of lastMigrations.rows) {
        await this.rollbackMigration(migration);
      }

      console.log(`Rolled back ${lastMigrations.rows.length} migrations`);
    } finally {
      await this.releaseLock(client);
    }
  }

  async rollbackMigration(migration) {
    console.log(`Rolling back migration: ${migration.name}`);
    
    const client = await this.pool.connect();
    try {
      await client.query('BEGIN');

      if (migration.rollback_sql) {
        await client.query(migration.rollback_sql);
      } else {
        console.warn(`No rollback SQL available for ${migration.name}`);
      }

      await client.query(
        'DELETE FROM schema_migrations WHERE version = $1',
        [migration.version]
      );

      await client.query('COMMIT');
      console.log(`✓ Rolled back migration: ${migration.name}`);

    } catch (error) {
      await client.query('ROLLBACK');
      console.error(`✗ Rollback failed for ${migration.name}:`, error.message);
      throw error;
    } finally {
      client.release();
    }
  }
}

module.exports = MigrationManager;

  3. Migration File Templates

    • Create standardized migration templates:

    SQL Migration Template:

    -- +migrate Up
-- Migration: Add user preferences table
-- Author: Developer Name
-- Date: 2024-01-15
-- Description: Create user_preferences table to store user-specific settings

CREATE TABLE user_preferences (
  id BIGSERIAL PRIMARY KEY,
  user_id BIGINT NOT NULL REFERENCES users(id) ON DELETE CASCADE,
  category VARCHAR(100) NOT NULL,
  key VARCHAR(100) NOT NULL,
  value JSONB NOT NULL DEFAULT '{}',
  created_at TIMESTAMP WITH TIME ZONE DEFAULT CURRENT_TIMESTAMP,
  updated_at TIMESTAMP WITH TIME ZONE DEFAULT CURRENT_TIMESTAMP,
  
  UNIQUE(user_id, category, key)
);

-- Add indexes for efficient querying
CREATE INDEX idx_user_preferences_user_id ON user_preferences(user_id);
CREATE INDEX idx_user_preferences_category ON user_preferences(category);
CREATE INDEX idx_user_preferences_key ON user_preferences(key);

-- Add comments for documentation
COMMENT ON TABLE user_preferences IS 'User-specific preference settings organized by category';
COMMENT ON COLUMN user_preferences.category IS 'Preference category (e.g., notifications, display, privacy)';
COMMENT ON COLUMN user_preferences.key IS 'Specific preference key within the category';
COMMENT ON COLUMN user_preferences.value IS 'Preference value stored as JSONB for flexibility';

-- +migrate Down
-- Rollback: Remove user preferences table

DROP TABLE IF EXISTS user_preferences CASCADE;

    JavaScript Migration Template:

    // migrations/20240115120000_add_user_preferences.js
const migration = {
  name: 'Add user preferences table',
  description: 'Create user_preferences table for storing user-specific settings',
  
  async up(client) {
    console.log('Creating user_preferences table...');
    
    await client.query(`
      CREATE TABLE user_preferences (
        id BIGSERIAL PRIMARY KEY,
        user_id BIGINT NOT NULL REFERENCES users(id) ON DELETE CASCADE,
        category VARCHAR(100) NOT NULL,
        key VARCHAR(100) NOT NULL,
        value JSONB NOT NULL DEFAULT '{}',
        created_at TIMESTAMP WITH TIME ZONE DEFAULT CURRENT_TIMESTAMP,
        updated_at TIMESTAMP WITH TIME ZONE DEFAULT CURRENT_TIMESTAMP,
        
        UNIQUE(user_id, category, key)
      );
    `);

    await client.query(`
      CREATE INDEX idx_user_preferences_user_id ON user_preferences(user_id);
    `);

    await client.query(`
      CREATE INDEX idx_user_preferences_category ON user_preferences(category);
    `);

    console.log('✓ user_preferences table created successfully');
  },

  async down(client) {
    console.log('Dropping user_preferences table...');
    
    await client.query('DROP TABLE IF EXISTS user_preferences CASCADE;');
    
    console.log('✓ user_preferences table dropped successfully');
  }
};

module.exports = migration;

  4. Advanced Migration Patterns

    • Implement complex migration scenarios:

    Data Migration with Validation:

    // migrations/20240115130000_migrate_user_settings.js
const migration = {
  name: 'Migrate user settings to new format',
  description: 'Transform legacy user_settings JSONB column to normalized user_preferences table',
  
  async up(client) {
    console.log('Starting user settings migration...');
    
    // Step 1: Create temporary backup
    await client.query(`
      CREATE TABLE user_settings_backup AS 
      SELECT * FROM users WHERE settings IS NOT NULL;
    `);
    
    console.log('✓ Created backup of existing user settings');

    // Step 2: Migrate data in batches
    const batchSize = 1000;
    let offset = 0;
    let processedCount = 0;

    while (true) {
      const result = await client.query(`
        SELECT id, settings 
        FROM users 
        WHERE settings IS NOT NULL 
        ORDER BY id 
        LIMIT $1 OFFSET $2
      `, [batchSize, offset]);

      if (result.rows.length === 0) break;

      for (const user of result.rows) {
        await this.migrateUserSettings(client, user.id, user.settings);
        processedCount++;
      }

      offset += batchSize;
      console.log(`✓ Processed ${processedCount} users...`);
    }

    // Step 3: Validate migration
    const validationResult = await this.validateMigration(client);
    if (!validationResult.isValid) {
      throw new Error(`Migration validation failed: ${validationResult.errors.join(', ')}`);
    }

    console.log(`✓ Successfully migrated ${processedCount} user settings`);
  },

  async migrateUserSettings(client, userId, settings) {
    const settingsObj = typeof settings === 'string' ? JSON.parse(settings) : settings;
    
    for (const [category, categorySettings] of Object.entries(settingsObj)) {
      if (typeof categorySettings === 'object') {
        for (const [key, value] of Object.entries(categorySettings)) {
          await client.query(`
            INSERT INTO user_preferences (user_id, category, key, value)
            VALUES ($1, $2, $3, $4)
            ON CONFLICT (user_id, category, key) DO UPDATE
            SET value = $4, updated_at = CURRENT_TIMESTAMP
          `, [userId, category, key, JSON.stringify(value)]);
        }
      } else {
        // Handle flat settings structure
        await client.query(`
          INSERT INTO user_preferences (user_id, category, key, value)
          VALUES ($1, $2, $3, $4)
          ON CONFLICT (user_id, category, key) DO UPDATE
          SET value = $4, updated_at = CURRENT_TIMESTAMP
        `, [userId, 'general', category, JSON.stringify(categorySettings)]);
      }
    }
  },

  async validateMigration(client) {
    const errors = [];
    
    // Check for data consistency
    const oldCount = await client.query(
      'SELECT COUNT(*) FROM users WHERE settings IS NOT NULL'
    );
    
    const newCount = await client.query(
      'SELECT COUNT(DISTINCT user_id) FROM user_preferences'
    );

    if (oldCount.rows[0].count !== newCount.rows[0].count) {
      errors.push(`User count mismatch: ${oldCount.rows[0].count} vs ${newCount.rows[0].count}`);
    }

    // Check for required preferences
    const missingPrefs = await client.query(`
      SELECT u.id FROM users u
      LEFT JOIN user_preferences up ON u.id = up.user_id
      WHERE u.settings IS NOT NULL AND up.user_id IS NULL
    `);

    if (missingPrefs.rows.length > 0) {
      errors.push(`${missingPrefs.rows.length} users missing preferences`);
    }

    return {
      isValid: errors.length === 0,
      errors
    };
  },

  async down(client) {
    console.log('Rolling back user settings migration...');
    
    // Restore from backup
    await client.query(`
      UPDATE users 
      SET settings = backup.settings
      FROM user_settings_backup backup
      WHERE users.id = backup.id;
    `);
    
    // Clean up
    await client.query('DELETE FROM user_preferences;');
    await client.query('DROP TABLE user_settings_backup;');
    
    console.log('✓ Rollback completed');
  }
};

module.exports = migration;

  5. Schema Alteration Migrations

    • Handle schema changes safely:

    Safe Column Addition:

    -- +migrate Up
-- Migration: Add email verification tracking
-- Safe column addition with default values

-- Add new columns with safe defaults
ALTER TABLE users 
ADD COLUMN email_verification_token VARCHAR(255),
ADD COLUMN email_verification_expires_at TIMESTAMP WITH TIME ZONE,
ADD COLUMN email_verification_attempts INTEGER DEFAULT 0;

-- Add index for token lookup
CREATE INDEX CONCURRENTLY idx_users_email_verification_token 
ON users(email_verification_token) 
WHERE email_verification_token IS NOT NULL;

-- Add constraint for expiration logic
ALTER TABLE users 
ADD CONSTRAINT chk_email_verification_expires 
CHECK (
  (email_verification_token IS NULL AND email_verification_expires_at IS NULL) OR
  (email_verification_token IS NOT NULL AND email_verification_expires_at IS NOT NULL)
);

-- +migrate Down
-- Remove email verification columns

DROP INDEX IF EXISTS idx_users_email_verification_token;
ALTER TABLE users 
DROP CONSTRAINT IF EXISTS chk_email_verification_expires,
DROP COLUMN IF EXISTS email_verification_token,
DROP COLUMN IF EXISTS email_verification_expires_at,
DROP COLUMN IF EXISTS email_verification_attempts;

    Safe Table Restructuring:

    -- +migrate Up
-- Migration: Split user addresses into separate table
-- Zero-downtime table restructuring

-- Step 1: Create new addresses table
CREATE TABLE user_addresses (
  id BIGSERIAL PRIMARY KEY,
  user_id BIGINT NOT NULL REFERENCES users(id) ON DELETE CASCADE,
  type address_type DEFAULT 'shipping',
  first_name VARCHAR(100),
  last_name VARCHAR(100),
  company VARCHAR(255),
  address_line_1 VARCHAR(255) NOT NULL,
  address_line_2 VARCHAR(255),
  city VARCHAR(100) NOT NULL,
  state VARCHAR(100),
  postal_code VARCHAR(20),
  country CHAR(2) NOT NULL DEFAULT 'US',
  phone VARCHAR(20),
  is_default BOOLEAN DEFAULT FALSE,
  created_at TIMESTAMP WITH TIME ZONE DEFAULT CURRENT_TIMESTAMP,
  updated_at TIMESTAMP WITH TIME ZONE DEFAULT CURRENT_TIMESTAMP
);

CREATE TYPE address_type AS ENUM ('billing', 'shipping');

-- Add indexes
CREATE INDEX idx_user_addresses_user_id ON user_addresses(user_id);
CREATE INDEX idx_user_addresses_type ON user_addresses(type);
CREATE UNIQUE INDEX idx_user_addresses_default 
ON user_addresses(user_id, type) 
WHERE is_default = TRUE;

-- Step 2: Migrate existing address data
INSERT INTO user_addresses (
  user_id, type, first_name, last_name, address_line_1, 
  city, state, postal_code, country, is_default
)
SELECT 
  id, 'shipping', first_name, last_name, address,
  city, state, postal_code, 
  COALESCE(country, 'US'), TRUE
FROM users 
WHERE address IS NOT NULL;

-- Step 3: Create view for backward compatibility
CREATE VIEW users_with_address AS
SELECT 
  u.*,
  ua.address_line_1 as address,
  ua.city,
  ua.state,
  ua.postal_code,
  ua.country
FROM users u
LEFT JOIN user_addresses ua ON u.id = ua.user_id AND ua.is_default = TRUE AND ua.type = 'shipping';

-- Step 4: Add trigger to maintain view consistency
CREATE OR REPLACE FUNCTION sync_user_address()
RETURNS TRIGGER AS $$
BEGIN
  IF TG_OP = 'UPDATE' THEN
    -- Update default shipping address
    UPDATE user_addresses 
    SET 
      address_line_1 = NEW.address,
      city = NEW.city,
      state = NEW.state,
      postal_code = NEW.postal_code,
      country = NEW.country,
      updated_at = CURRENT_TIMESTAMP
    WHERE user_id = NEW.id AND type = 'shipping' AND is_default = TRUE;
    
    RETURN NEW;
  END IF;
  RETURN NULL;
END;
$$ LANGUAGE plpgsql;

CREATE TRIGGER trigger_sync_user_address
AFTER UPDATE ON users
FOR EACH ROW
WHEN (OLD.address IS DISTINCT FROM NEW.address OR 
      OLD.city IS DISTINCT FROM NEW.city OR
      OLD.state IS DISTINCT FROM NEW.state OR
      OLD.postal_code IS DISTINCT FROM NEW.postal_code OR
      OLD.country IS DISTINCT FROM NEW.country)
EXECUTE FUNCTION sync_user_address();

-- +migrate Down
-- Restore original structure

DROP TRIGGER IF EXISTS trigger_sync_user_address ON users;
DROP FUNCTION IF EXISTS sync_user_address();
DROP VIEW IF EXISTS users_with_address;
DROP TABLE IF EXISTS user_addresses CASCADE;
DROP TYPE IF EXISTS address_type;

  6. Migration Testing Framework

    • Test migrations thoroughly:

    Migration Test Suite:

    // tests/migration-tests.js
const { Pool } = require('pg');
const MigrationManager = require('../migrations/migration-framework');

class MigrationTester {
  constructor() {
    this.testDbConfig = {
      host: process.env.TEST_DB_HOST || 'localhost',
      port: process.env.TEST_DB_PORT || 5432,
      database: process.env.TEST_DB_NAME || 'test_db',
      user: process.env.TEST_DB_USER || 'postgres',
      password: process.env.TEST_DB_PASSWORD || 'password'
    };
    
    this.pool = new Pool(this.testDbConfig);
    this.migrationManager = new MigrationManager(this.testDbConfig);
  }

  async setupTestDatabase() {
    // Create fresh test database
    const adminPool = new Pool({
      ...this.testDbConfig,
      database: 'postgres'
    });

    try {
      await adminPool.query(`DROP DATABASE IF EXISTS ${this.testDbConfig.database}`);
      await adminPool.query(`CREATE DATABASE ${this.testDbConfig.database}`);
      console.log('✓ Test database created');
    } finally {
      await adminPool.end();
    }
  }

  async teardownTestDatabase() {
    await this.pool.end();
    
    const adminPool = new Pool({
      ...this.testDbConfig,
      database: 'postgres'
    });

    try {
      await adminPool.query(`DROP DATABASE IF EXISTS ${this.testDbConfig.database}`);
      console.log('✓ Test database cleaned up');
    } finally {
      await adminPool.end();
    }
  }

  async testMigrationUpDown(migrationFile) {
    console.log(`Testing migration: ${migrationFile}`);
    
    try {
      // Test migration up
      const startTime = Date.now();
      await this.migrationManager.runMigration({ file: migrationFile });
      const upTime = Date.now() - startTime;
      
      console.log(`✓ Migration up completed in ${upTime}ms`);

      // Verify migration was recorded
      const migrationRecord = await this.pool.query(
        'SELECT * FROM schema_migrations WHERE name = $1',
        [migrationFile]
      );
      
      if (migrationRecord.rows.length === 0) {
        throw new Error('Migration not recorded in schema_migrations table');
      }

      // Test migration down
      const rollbackStartTime = Date.now();
      await this.migrationManager.rollbackMigration(migrationRecord.rows[0]);
      const downTime = Date.now() - rollbackStartTime;
      
      console.log(`✓ Migration down completed in ${downTime}ms`);

      // Verify migration was removed
      const afterRollback = await this.pool.query(
        'SELECT * FROM schema_migrations WHERE name = $1',
        [migrationFile]
      );
      
      if (afterRollback.rows.length > 0) {
        throw new Error('Migration not removed after rollback');
      }

      return {
        success: true,
        upTime,
        downTime,
        migrationFile
      };

    } catch (error) {
      console.error(`✗ Migration test failed: ${error.message}`);
      return {
        success: false,
        error: error.message,
        migrationFile
      };
    }
  }

  async testDataIntegrity(testData) {
    console.log('Testing data integrity...');
    
    // Insert test data
    const insertResults = [];
    for (const table of Object.keys(testData)) {
      for (const record of testData[table]) {
        try {
          const columns = Object.keys(record);
          const values = Object.values(record);
          const placeholders = values.map((_, i) => `$${i + 1}`).join(', ');
          
          const result = await this.pool.query(
            `INSERT INTO ${table} (${columns.join(', ')}) VALUES (${placeholders}) RETURNING id`,
            values
          );
          
          insertResults.push({
            table,
            id: result.rows[0].id,
            success: true
          });
        } catch (error) {
          insertResults.push({
            table,
            success: false,
            error: error.message
          });
        }
      }
    }

    return insertResults;
  }

  async testPerformance(queries) {
    console.log('Testing query performance...');
    
    const performanceResults = [];
    
    for (const query of queries) {
      const startTime = process.hrtime.bigint();
      
      try {
        const result = await this.pool.query(query.sql, query.params || []);
        const endTime = process.hrtime.bigint();
        const duration = Number(endTime - startTime) / 1000000; // Convert to milliseconds
        
        performanceResults.push({
          name: query.name,
          duration,
          rowCount: result.rows.length,
          success: true
        });
        
        if (duration > (query.maxDuration || 1000)) {
          console.warn(`⚠ Query ${query.name} took ${duration}ms (expected < ${query.maxDuration || 1000}ms)`);
        }
        
      } catch (error) {
        performanceResults.push({
          name: query.name,
          success: false,
          error: error.message
        });
      }
    }

    return performanceResults;
  }

  async runFullTestSuite() {
    console.log('Starting migration test suite...');
    
    await this.setupTestDatabase();
    await this.migrationManager.initialize();
    
    try {
      const testResults = {
        migrations: [],
        dataIntegrity: [],
        performance: [],
        summary: { passed: 0, failed: 0 }
      };

      // Test all migration files
      const migrationFiles = await this.migrationManager.getPendingMigrations();
      
      for (const migration of migrationFiles) {
        const result = await this.testMigrationUpDown(migration.file);
        testResults.migrations.push(result);
        
        if (result.success) {
          testResults.summary.passed++;
        } else {
          testResults.summary.failed++;
        }
      }

      console.log('\n📊 Test Results Summary:');
      console.log(`✓ Passed: ${testResults.summary.passed}`);
      console.log(`✗ Failed: ${testResults.summary.failed}`);
      console.log(`📈 Success Rate: ${(testResults.summary.passed / (testResults.summary.passed + testResults.summary.failed) * 100).toFixed(1)}%`);

      return testResults;

    } finally {
      await this.teardownTestDatabase();
    }
  }
}

module.exports = MigrationTester;

// CLI usage
if (require.main === module) {
  const tester = new MigrationTester();
  tester.runFullTestSuite()
    .then(results => {
      console.log('\nTest suite completed');
      process.exit(results.summary.failed > 0 ? 1 : 0);
    })
    .catch(error => {
      console.error('Test suite failed:', error);
      process.exit(1);
    });
}

  7. Production Migration Safety

    • Implement production-safe migration practices:

    Safe Production Migration:

    // migrations/production-safety.js
class ProductionMigrationSafety {
  static async validateProductionMigration(migrationFile, pool) {
    const safety = new ProductionMigrationSafety(pool);
    
    const checks = [
      safety.checkTableLocks.bind(safety),
      safety.checkDataSize.bind(safety),
      safety.checkDependencies.bind(safety),
      safety.checkBackupStatus.bind(safety),
      safety.checkMaintenanceWindow.bind(safety)
    ];

    const results = [];
    for (const check of checks) {
      const result = await check(migrationFile);
      results.push(result);
      
      if (!result.passed && result.blocking) {
        throw new Error(`Migration blocked: ${result.message}`);
      }
    }

    return results;
  }

  constructor(pool) {
    this.pool = pool;
  }

  async checkTableLocks(migrationFile) {
    // Check for long-running transactions that might block migration
    const longTransactions = await this.pool.query(`
      SELECT 
        pid,
        now() - pg_stat_activity.query_start AS duration,
        query,
        state
      FROM pg_stat_activity 
      WHERE (now() - pg_stat_activity.query_start) > interval '5 minutes'
      AND state IN ('active', 'idle in transaction');
    `);

    return {
      name: 'table_locks',
      passed: longTransactions.rows.length === 0,
      blocking: true,
      message: longTransactions.rows.length > 0 
        ? `${longTransactions.rows.length} long-running transactions detected`
        : 'No blocking transactions found',
      details: longTransactions.rows
    };
  }

  async checkDataSize(migrationFile) {
    // Estimate migration impact based on data size
    const tableSizes = await this.pool.query(`
      SELECT 
        schemaname,
        tablename,
        pg_size_pretty(pg_total_relation_size(schemaname||'.'||tablename)) as size,
        pg_total_relation_size(schemaname||'.'||tablename) as size_bytes
      FROM pg_tables 
      WHERE schemaname = 'public'
      ORDER BY pg_total_relation_size(schemaname||'.'||tablename) DESC;
    `);

    const largeTables = tableSizes.rows.filter(table => table.size_bytes > 1000000000); // > 1GB

    return {
      name: 'data_size',
      passed: largeTables.length < 5,
      blocking: false,
      message: `${largeTables.length} tables > 1GB found`,
      details: largeTables
    };
  }

  async checkDependencies(migrationFile) {
    // Check for dependent applications or services
    const activeConnections = await this.pool.query(`
      SELECT 
        application_name,
        COUNT(*) as connection_count,
        COUNT(*) FILTER (WHERE state = 'active') as active_count
      FROM pg_stat_activity 
      WHERE datname = current_database()
      AND application_name IS NOT NULL
      GROUP BY application_name
      ORDER BY connection_count DESC;
    `);

    const highUsage = activeConnections.rows.filter(app => app.active_count > 10);

    return {
      name: 'dependencies',
      passed: highUsage.length === 0,
      blocking: false,
      message: highUsage.length > 0 
        ? `${highUsage.length} applications with high database usage`
        : 'Database usage within acceptable limits',
      details: activeConnections.rows
    };
  }

  async checkBackupStatus(migrationFile) {
    // Verify recent backup exists
    const lastBackup = await this.pool.query(`
      SELECT 
        pg_last_wal_receive_lsn(),
        pg_last_wal_replay_lsn(),
        EXTRACT(EPOCH FROM (now() - pg_stat_file('base/backup_label', true).modification))::int as backup_age_seconds
      WHERE pg_stat_file('base/backup_label', true) IS NOT NULL;
    `);

    const backupExists = lastBackup.rows.length > 0;
    const backupAge = backupExists ? lastBackup.rows[0].backup_age_seconds : null;
    const isRecentBackup = backupAge !== null && backupAge < 86400; // 24 hours

    return {
      name: 'backup_status',
      passed: isRecentBackup,
      blocking: true,
      message: isRecentBackup 
        ? `Recent backup available (${Math.round(backupAge / 3600)} hours old)`
        : 'No recent backup found - backup required before migration',
      details: { backupExists, backupAge }
    };
  }

  async checkMaintenanceWindow(migrationFile) {
    // Check if we're in approved maintenance window
    const now = new Date();
    const hour = now.getUTCHours();
    const dayOfWeek = now.getUTCDay();
    
    // Define maintenance windows (UTC)
    const maintenanceWindows = [
      { days: [0, 6], startHour: 2, endHour: 6 }, // Weekend early morning
      { days: [1, 2, 3, 4, 5], startHour: 3, endHour: 5 } // Weekday early morning
    ];

    const inMaintenanceWindow = maintenanceWindows.some(window => 
      window.days.includes(dayOfWeek) && 
      hour >= window.startHour && 
      hour < window.endHour
    );

    return {
      name: 'maintenance_window',
      passed: inMaintenanceWindow,
      blocking: false,
      message: inMaintenanceWindow 
        ? 'Currently in maintenance window'
        : `Outside maintenance window (current UTC hour: ${hour})`,
      details: { currentHour: hour, dayOfWeek, maintenanceWindows }
    };
  }
}

module.exports = ProductionMigrationSafety;

  8. Migration Monitoring and Alerting

    • Monitor migration execution:

    Migration Monitoring:

    // migrations/migration-monitor.js
class MigrationMonitor {
  constructor(alertService) {
    this.alertService = alertService;
    this.metrics = {
      executionTimes: [],
      errorCounts: {},
      successCounts: {}
    };
  }

  async monitorMigration(migrationName, migrationFn) {
    const startTime = Date.now();
    const memoryBefore = process.memoryUsage();
    
    try {
      console.log(`🚀 Starting migration: ${migrationName}`);
      
      const result = await migrationFn();
      
      const endTime = Date.now();
      const duration = endTime - startTime;
      const memoryAfter = process.memoryUsage();
      
      // Record success metrics
      this.recordSuccess(migrationName, duration, memoryAfter.heapUsed - memoryBefore.heapUsed);
      
      // Alert on long-running migrations
      if (duration > 300000) { // 5 minutes
        await this.alertService.sendAlert({
          type: 'warning',
          title: 'Long-running migration',
          message: `Migration ${migrationName} took ${duration}ms to complete`,
          severity: duration > 600000 ? 'high' : 'medium'
        });
      }

      console.log(`✅ Migration completed: ${migrationName} (${duration}ms)`);
      return result;

    } catch (error) {
      const duration = Date.now() - startTime;
      
      // Record error metrics
      this.recordError(migrationName, error, duration);
      
      // Send error alert
      await this.alertService.sendAlert({
        type: 'error',
        title: 'Migration failed',
        message: `Migration ${migrationName} failed: ${error.message}`,
        severity: 'critical',
        details: {
          migrationName,
          duration,
          error: error.message,
          stack: error.stack
        }
      });

      console.error(`❌ Migration failed: ${migrationName}`, error);
      throw error;
    }
  }

  recordSuccess(migrationName, duration, memoryDelta) {
    this.metrics.executionTimes.push({
      migration: migrationName,
      duration,
      memoryDelta,
      timestamp: new Date()
    });
    
    this.metrics.successCounts[migrationName] = 
      (this.metrics.successCounts[migrationName] || 0) + 1;
  }

  recordError(migrationName, error, duration) {
    this.metrics.errorCounts[migrationName] = 
      (this.metrics.errorCounts[migrationName] || 0) + 1;

    // Log detailed error information
    console.error('Migration Error Details:', {
      migration: migrationName,
      duration,
      error: error.message,
      stack: error.stack,
      timestamp: new Date()
    });
  }

  getMetrics() {
    return {
      averageExecutionTime: this.calculateAverageExecutionTime(),
      totalMigrations: this.metrics.executionTimes.length,
      successRate: this.calculateSuccessRate(),
      errorCounts: this.metrics.errorCounts,
      recentMigrations: this.metrics.executionTimes.slice(-10)
    };
  }

  calculateAverageExecutionTime() {
    if (this.metrics.executionTimes.length === 0) return 0;
    
    const total = this.metrics.executionTimes.reduce((sum, record) => sum + record.duration, 0);
    return Math.round(total / this.metrics.executionTimes.length);
  }

  calculateSuccessRate() {
    const totalSuccess = Object.values(this.metrics.successCounts).reduce((sum, count) => sum + count, 0);
    const totalErrors = Object.values(this.metrics.errorCounts).reduce((sum, count) => sum + count, 0);
    const total = totalSuccess + totalErrors;
    
    return total > 0 ? (totalSuccess / total * 100).toFixed(2) : 100;
  }
}

module.exports = MigrationMonitor;

  9. Migration CLI Tools

    • Create comprehensive CLI interface:

    Migration CLI:

    #!/usr/bin/env node
// bin/migrate.js
const yargs = require('yargs');
const MigrationManager = require('../migrations/migration-framework');
const MigrationTester = require('../tests/migration-tests');
const MigrationMonitor = require('../migrations/migration-monitor');

const dbConfig = {
  host: process.env.DB_HOST || 'localhost',
  port: process.env.DB_PORT || 5432,
  database: process.env.DB_NAME || 'myapp',
  user: process.env.DB_USER || 'postgres',
  password: process.env.DB_PASSWORD
};

const migrationManager = new MigrationManager(dbConfig);

yargs
  .command('up', 'Run pending migrations', {}, async () => {
    try {
      await migrationManager.migrate();
      console.log('✅ Migrations completed successfully');
      process.exit(0);
    } catch (error) {
      console.error('❌ Migration failed:', error.message);
      process.exit(1);
    }
  })
  .command('down [steps]', 'Rollback migrations', {
    steps: {
      describe: 'Number of migrations to rollback',
      type: 'number',
      default: 1
    }
  }, async (argv) => {
    try {
      await migrationManager.rollback(argv.steps);
      console.log(`✅ Rolled back ${argv.steps} migration(s)`);
      process.exit(0);
    } catch (error) {
      console.error('❌ Rollback failed:', error.message);
      process.exit(1);
    }
  })
  .command('status', 'Show migration status', {}, async () => {
    try {
      const pending = await migrationManager.getPendingMigrations();
      const executed = await migrationManager.pool.query(
        'SELECT version, name, executed_at FROM schema_migrations ORDER BY executed_at DESC'
      );

      console.log('\n📊 Migration Status:');
      console.log(`✅ Executed: ${executed.rows.length}`);
      console.log(`⏳ Pending: ${pending.length}`);
      
      if (pending.length > 0) {
        console.log('\n⏳ Pending Migrations:');
        pending.forEach(m => console.log(`  - ${m.file}`));
      }
      
      if (executed.rows.length > 0) {
        console.log('\n✅ Recent Migrations:');
        executed.rows.slice(0, 5).forEach(m => 
          console.log(`  - ${m.name} (${m.executed_at.toISOString()})`)
        );
      }
      
      process.exit(0);
    } catch (error) {
      console.error('❌ Status check failed:', error.message);
      process.exit(1);
    }
  })
  .command('test', 'Test migrations', {}, async () => {
    try {
      const tester = new MigrationTester();
      const results = await tester.runFullTestSuite();
      
      if (results.summary.failed > 0) {
        console.error(`❌ ${results.summary.failed} migration tests failed`);
        process.exit(1);
      } else {
        console.log(`✅ All ${results.summary.passed} migration tests passed`);
        process.exit(0);
      }
    } catch (error) {
      console.error('❌ Migration testing failed:', error.message);
      process.exit(1);
    }
  })
  .command('create <name>', 'Create new migration file', {
    name: {
      describe: 'Migration name',
      type: 'string',
      demandOption: true
    }
  }, async (argv) => {
    try {
      const timestamp = new Date().toISOString().replace(/[-:T]/g, '').slice(0, 14);
      const filename = `${timestamp}_${argv.name.replace(/[^a-zA-Z0-9]/g, '_')}.sql`;
      const filepath = path.join(__dirname, '../migrations', filename);
      
      const template = `-- +migrate Up

-- Migration: ${argv.name} -- Author: ${process.env.USER || 'Unknown'} -- Date: ${new Date().toISOString().split('T')[0]} -- Description: [Add description here]

-- Add your migration SQL here

-- +migrate Down -- Rollback: ${argv.name}

-- Add your rollback SQL here `;

     await fs.writeFile(filepath, template);
     console.log(`✅ Created migration file: ${filename}`);
     console.log(`📝 Edit the file at: ${filepath}`);
     process.exit(0);
   } catch (error) {
     console.error('❌ Failed to create migration:', error.message);
     process.exit(1);
   }
 })
 .demandCommand()
 .help()
 .argv;


10. **Production Deployment Integration**
 - Integrate with deployment pipelines:

 **CI/CD Integration:**
 ```yaml
 # .github/workflows/database-migration.yml
 name: Database Migration

 on:
   push:
     branches: [main]
     paths: ['migrations/**']
   
 jobs:
   test-migrations:
     runs-on: ubuntu-latest
     services:
       postgres:
         image: postgres:13
         env:
           POSTGRES_PASSWORD: postgres
           POSTGRES_DB: test_db
         options: >-
           --health-cmd pg_isready
           --health-interval 10s
           --health-timeout 5s
           --health-retries 5

     steps:
       - uses: actions/checkout@v2
       
       - name: Setup Node.js
         uses: actions/setup-node@v2
         with:
           node-version: '16'
           
       - name: Install dependencies
         run: npm ci
         
       - name: Test migrations
         env:
           TEST_DB_HOST: localhost
           TEST_DB_PORT: 5432
           TEST_DB_NAME: test_db
           TEST_DB_USER: postgres
           TEST_DB_PASSWORD: postgres
         run: npm run migrate:test
         
       - name: Check migration safety
         run: npm run migrate:safety-check
         
   deploy-migrations:
     needs: test-migrations
     runs-on: ubuntu-latest
     if: github.ref == 'refs/heads/main'
     
     steps:
       - uses: actions/checkout@v2
       
       - name: Setup Node.js
         uses: actions/setup-node@v2
         with:
           node-version: '16'
           
       - name: Install dependencies
         run: npm ci
         
       - name: Run production migrations
         env:
           DB_HOST: ${{ secrets.PROD_DB_HOST }}
           DB_PORT: ${{ secrets.PROD_DB_PORT }}
           DB_NAME: ${{ secrets.PROD_DB_NAME }}
           DB_USER: ${{ secrets.PROD_DB_USER }}
           DB_PASSWORD: ${{ secrets.PROD_DB_PASSWORD }}
         run: |
           npm run migrate:production:safety-check
           npm run migrate:up
           
       - name: Verify deployment
         env:
           DB_HOST: ${{ secrets.PROD_DB_HOST }}
           DB_PORT: ${{ secrets.PROD_DB_PORT }}
           DB_NAME: ${{ secrets.PROD_DB_NAME }}
           DB_USER: ${{ secrets.PROD_DB_USER }}
           DB_PASSWORD: ${{ secrets.PROD_DB_PASSWORD }}
         run: npm run migrate:verify
 ```