# Database Migration Strategy: Single-Tenant to Multi-Tenant

## Table of Contents

1. [Migration Overview](#migration-overview)
2. [Pre-Migration Checklist](#pre-migration-checklist)
3. [Database Migration Steps](#database-migration-steps)
4. [EF Core Migrations](#ef-core-migrations)
5. [Code Migration Steps](#code-migration-steps)
6. [Testing Migration](#testing-migration)
7. [Deployment Plan](#deployment-plan)
8. [Rollback Plan](#rollback-plan)
9. [Post-Migration Validation](#post-migration-validation)

---

## Migration Overview

### Objective

Transform ColaFlow from a single-tenant system to a **multi-tenant system** with:
- Tenant isolation via `tenant_id` column in all tables
- Default tenant created for existing data
- Zero data loss
- Minimal downtime

### Strategy

**Approach**: Create default tenant and migrate all existing data to it

```
Single-Tenant System (Before)
┌──────────────────┐
│  users           │
│  - id            │
│  - email         │
│  - password_hash │
└──────────────────┘

Multi-Tenant System (After)
┌──────────────────┐      ┌──────────────────┐
│  tenants         │      │  users           │
│  - id            │◄─────│  - id            │
│  - name          │      │  - tenant_id (FK)│
│  - slug          │      │  - email         │
└──────────────────┘      │  - password_hash │
                          └──────────────────┘
```

### Timeline

| Phase | Duration | Description |
|-------|----------|-------------|
| **Phase 1: Preparation** | 1 day | Backup, validation, test environment |
| **Phase 2: Database Migration** | 2-3 hours | Execute SQL scripts, create default tenant |
| **Phase 3: Code Deployment** | 1 hour | Deploy updated application code |
| **Phase 4: Validation** | 2 hours | Smoke tests, data validation |
| **Phase 5: Monitoring** | 1 week | Monitor production for issues |

**Total Expected Downtime**: 30-60 minutes (during Phase 2)

---

## Pre-Migration Checklist

### ✅ Before Starting Migration

- [ ] **Full database backup** completed and verified
- [ ] **Test environment** migration completed successfully
- [ ] **All tests passing** in test environment
- [ ] **Migration scripts** reviewed and approved
- [ ] **Rollback scripts** prepared and tested
- [ ] **Team notified** of maintenance window
- [ ] **Users notified** of scheduled downtime
- [ ] **Monitoring** alerts configured
- [ ] **Database connection strings** updated in configuration
- [ ] **EF Core migrations** generated and reviewed

### ⚠️ Migration Risks

| Risk | Impact | Mitigation |
|------|--------|------------|
| Data loss | Critical | Full backup before migration |
| Extended downtime | High | Test migration in staging first |
| Foreign key violations | High | Disable FK checks during migration |
| NULL constraint violations | Medium | Fill tenant_id before setting NOT NULL |
| Performance degradation | Medium | Add indexes after migration |
| Application errors | High | Deploy code and DB together |

---

## Database Migration Steps

### Step 1: Create Tenants Table

```sql
-- Create tenants table
CREATE TABLE tenants (
    id UUID PRIMARY KEY DEFAULT gen_random_uuid(),
    name VARCHAR(100) NOT NULL,
    slug VARCHAR(50) NOT NULL UNIQUE,
    status INT NOT NULL DEFAULT 1, -- 1=Active, 2=Suspended, 3=Cancelled
    plan INT NOT NULL DEFAULT 1,   -- 1=Free, 2=Pro, 3=Enterprise

    -- SSO Configuration (stored as JSONB)
    sso_config JSONB NULL,

    -- Limits
    max_users INT NOT NULL DEFAULT 5,
    max_projects INT NOT NULL DEFAULT 3,
    max_storage_gb INT NOT NULL DEFAULT 2,

    -- Status tracking
    created_at TIMESTAMP NOT NULL DEFAULT NOW(),
    updated_at TIMESTAMP NULL,
    suspended_at TIMESTAMP NULL,
    suspension_reason TEXT NULL,

    CONSTRAINT chk_slug_format CHECK (slug ~ '^[a-z0-9]+(?:-[a-z0-9]+)*$')
);

-- Indexes
CREATE INDEX idx_tenants_slug ON tenants(slug);
CREATE INDEX idx_tenants_status ON tenants(status);
CREATE INDEX idx_tenants_plan ON tenants(plan);

-- Comments
COMMENT ON TABLE tenants IS 'Multi-tenant organizations';
COMMENT ON COLUMN tenants.slug IS 'URL-safe identifier (used in subdomains)';
```

### Step 2: Create Default Tenant

```sql
-- Insert default tenant for existing data
-- IMPORTANT: Save this UUID - you'll need it for data migration
INSERT INTO tenants (
    id,
    name,
    slug,
    status,
    plan,
    max_users,
    max_projects,
    max_storage_gb,
    created_at
) VALUES (
    'ffffffff-ffff-ffff-ffff-ffffffffffff', -- Use a well-known UUID for default tenant
    'Default Organization',
    'default',
    1, -- Active
    3, -- Enterprise
    999999,
    999999,
    999999,
    NOW()
);

-- Verify creation
SELECT * FROM tenants WHERE slug = 'default';
```

### Step 3: Add tenant_id Columns (Allow NULL Initially)

```sql
-- Users table
ALTER TABLE users ADD COLUMN tenant_id UUID NULL;
ALTER TABLE users ADD CONSTRAINT fk_users_tenant
    FOREIGN KEY (tenant_id) REFERENCES tenants(id) ON DELETE CASCADE;

-- Add tenant_id to ALL business tables
-- Projects
ALTER TABLE projects ADD COLUMN tenant_id UUID NULL;
ALTER TABLE projects ADD CONSTRAINT fk_projects_tenant
    FOREIGN KEY (tenant_id) REFERENCES tenants(id) ON DELETE CASCADE;

-- Issues
ALTER TABLE issues ADD COLUMN tenant_id UUID NULL;
ALTER TABLE issues ADD CONSTRAINT fk_issues_tenant
    FOREIGN KEY (tenant_id) REFERENCES tenants(id) ON DELETE CASCADE;

-- Epics
ALTER TABLE epics ADD COLUMN tenant_id UUID NULL;
ALTER TABLE epics ADD CONSTRAINT fk_epics_tenant
    FOREIGN KEY (tenant_id) REFERENCES tenants(id) ON DELETE CASCADE;

-- Sprints
ALTER TABLE sprints ADD COLUMN tenant_id UUID NULL;
ALTER TABLE sprints ADD CONSTRAINT fk_sprints_tenant
    FOREIGN KEY (tenant_id) REFERENCES tenants(id) ON DELETE CASCADE;

-- Issue Comments
ALTER TABLE issue_comments ADD COLUMN tenant_id UUID NULL;
ALTER TABLE issue_comments ADD CONSTRAINT fk_issue_comments_tenant
    FOREIGN KEY (tenant_id) REFERENCES tenants(id) ON DELETE CASCADE;

-- Attachments
ALTER TABLE attachments ADD COLUMN tenant_id UUID NULL;
ALTER TABLE attachments ADD CONSTRAINT fk_attachments_tenant
    FOREIGN KEY (tenant_id) REFERENCES tenants(id) ON DELETE CASCADE;

-- Add to ALL other business tables...
```

### Step 4: Migrate Existing Data to Default Tenant

```sql
-- Set the default tenant UUID
DO $$
DECLARE
    default_tenant_id UUID := 'ffffffff-ffff-ffff-ffff-ffffffffffff';
BEGIN
    -- Update users
    UPDATE users SET tenant_id = default_tenant_id WHERE tenant_id IS NULL;
    RAISE NOTICE 'Updated % users', (SELECT COUNT(*) FROM users WHERE tenant_id = default_tenant_id);

    -- Update projects
    UPDATE projects SET tenant_id = default_tenant_id WHERE tenant_id IS NULL;
    RAISE NOTICE 'Updated % projects', (SELECT COUNT(*) FROM projects WHERE tenant_id = default_tenant_id);

    -- Update issues
    UPDATE issues SET tenant_id = default_tenant_id WHERE tenant_id IS NULL;
    RAISE NOTICE 'Updated % issues', (SELECT COUNT(*) FROM issues WHERE tenant_id = default_tenant_id);

    -- Update epics
    UPDATE epics SET tenant_id = default_tenant_id WHERE tenant_id IS NULL;
    RAISE NOTICE 'Updated % epics', (SELECT COUNT(*) FROM epics WHERE tenant_id = default_tenant_id);

    -- Update sprints
    UPDATE sprints SET tenant_id = default_tenant_id WHERE tenant_id IS NULL;
    RAISE NOTICE 'Updated % sprints', (SELECT COUNT(*) FROM sprints WHERE tenant_id = default_tenant_id);

    -- Update issue_comments
    UPDATE issue_comments SET tenant_id = default_tenant_id WHERE tenant_id IS NULL;
    RAISE NOTICE 'Updated % issue_comments', (SELECT COUNT(*) FROM issue_comments WHERE tenant_id = default_tenant_id);

    -- Update attachments
    UPDATE attachments SET tenant_id = default_tenant_id WHERE tenant_id IS NULL;
    RAISE NOTICE 'Updated % attachments', (SELECT COUNT(*) FROM attachments WHERE tenant_id = default_tenant_id);

    -- Update ALL other tables...
END $$;
```

### Step 5: Validate Data Migration

```sql
-- Check for NULL tenant_id values (should be 0)
SELECT 'users' AS table_name, COUNT(*) AS null_count FROM users WHERE tenant_id IS NULL
UNION ALL
SELECT 'projects', COUNT(*) FROM projects WHERE tenant_id IS NULL
UNION ALL
SELECT 'issues', COUNT(*) FROM issues WHERE tenant_id IS NULL
UNION ALL
SELECT 'epics', COUNT(*) FROM epics WHERE tenant_id IS NULL
UNION ALL
SELECT 'sprints', COUNT(*) FROM sprints WHERE tenant_id IS NULL
UNION ALL
SELECT 'issue_comments', COUNT(*) FROM issue_comments WHERE tenant_id IS NULL
UNION ALL
SELECT 'attachments', COUNT(*) FROM attachments WHERE tenant_id IS NULL;

-- Expected output: All counts should be 0
```

### Step 6: Set tenant_id as NOT NULL

```sql
-- Now make tenant_id NOT NULL (all rows have values)
ALTER TABLE users ALTER COLUMN tenant_id SET NOT NULL;
ALTER TABLE projects ALTER COLUMN tenant_id SET NOT NULL;
ALTER TABLE issues ALTER COLUMN tenant_id SET NOT NULL;
ALTER TABLE epics ALTER COLUMN tenant_id SET NOT NULL;
ALTER TABLE sprints ALTER COLUMN tenant_id SET NOT NULL;
ALTER TABLE issue_comments ALTER COLUMN tenant_id SET NOT NULL;
ALTER TABLE attachments ALTER COLUMN tenant_id SET NOT NULL;

-- Add to ALL other tables...
```

### Step 7: Create Composite Indexes

```sql
-- CRITICAL: These indexes ensure query performance

-- Users
CREATE INDEX idx_users_tenant_id ON users(tenant_id);
CREATE INDEX idx_users_tenant_email ON users(tenant_id, email);
CREATE INDEX idx_users_tenant_status ON users(tenant_id, is_active);

-- Projects
CREATE INDEX idx_projects_tenant_id ON projects(tenant_id);
CREATE INDEX idx_projects_tenant_key ON projects(tenant_id, key);
CREATE INDEX idx_projects_tenant_status ON projects(tenant_id, status);
CREATE INDEX idx_projects_tenant_created ON projects(tenant_id, created_at DESC);

-- Issues
CREATE INDEX idx_issues_tenant_id ON issues(tenant_id);
CREATE INDEX idx_issues_tenant_project ON issues(tenant_id, project_id);
CREATE INDEX idx_issues_tenant_status ON issues(tenant_id, status);
CREATE INDEX idx_issues_tenant_assignee ON issues(tenant_id, assignee_id);
CREATE INDEX idx_issues_tenant_created ON issues(tenant_id, created_at DESC);

-- Epics
CREATE INDEX idx_epics_tenant_id ON epics(tenant_id);
CREATE INDEX idx_epics_tenant_project ON epics(tenant_id, project_id);

-- Sprints
CREATE INDEX idx_sprints_tenant_id ON sprints(tenant_id);
CREATE INDEX idx_sprints_tenant_project ON sprints(tenant_id, project_id);

-- Issue Comments
CREATE INDEX idx_issue_comments_tenant_id ON issue_comments(tenant_id);
CREATE INDEX idx_issue_comments_tenant_issue ON issue_comments(tenant_id, issue_id);

-- Attachments
CREATE INDEX idx_attachments_tenant_id ON attachments(tenant_id);

-- Add indexes to ALL other tables...
```

### Step 8: Update Unique Constraints

```sql
-- Update unique constraints to include tenant_id

-- Users: email should be unique per tenant (not globally)
ALTER TABLE users DROP CONSTRAINT IF EXISTS users_email_key;
ALTER TABLE users ADD CONSTRAINT uq_users_tenant_email UNIQUE (tenant_id, email);

-- Projects: key should be unique per tenant
ALTER TABLE projects DROP CONSTRAINT IF EXISTS projects_key_key;
ALTER TABLE projects ADD CONSTRAINT uq_projects_tenant_key UNIQUE (tenant_id, key);

-- Add similar constraints for other tables...
```

### Step 9: Add SSO-Related Columns to Users Table

```sql
-- Add SSO fields to users table
ALTER TABLE users ADD COLUMN auth_provider INT NOT NULL DEFAULT 1; -- 1=Local
ALTER TABLE users ADD COLUMN external_user_id VARCHAR(255) NULL;
ALTER TABLE users ADD COLUMN external_email VARCHAR(255) NULL;

-- Add unique constraint for SSO users
CREATE UNIQUE INDEX idx_users_tenant_provider_external
    ON users(tenant_id, auth_provider, external_user_id)
    WHERE external_user_id IS NOT NULL;

-- Add index for external lookups
CREATE INDEX idx_users_external_user_id
    ON users(external_user_id)
    WHERE external_user_id IS NOT NULL;
```

### Step 10: Create MCP Tokens Table

```sql
-- Create MCP tokens table
CREATE TABLE mcp_tokens (
    id UUID PRIMARY KEY DEFAULT gen_random_uuid(),
    tenant_id UUID NOT NULL REFERENCES tenants(id) ON DELETE CASCADE,
    user_id UUID NULL REFERENCES users(id) ON DELETE SET NULL,

    -- Token details
    name VARCHAR(100) NOT NULL,
    token_hash VARCHAR(255) NOT NULL UNIQUE,
    permissions JSONB NOT NULL,

    -- Status
    status INT NOT NULL DEFAULT 1, -- 1=Active, 2=Expired, 3=Revoked
    created_at TIMESTAMP NOT NULL DEFAULT NOW(),
    updated_at TIMESTAMP NULL,
    expires_at TIMESTAMP NULL,
    revoked_at TIMESTAMP NULL,
    revocation_reason TEXT NULL,

    -- Usage tracking
    last_used_at TIMESTAMP NULL,
    usage_count INT NOT NULL DEFAULT 0,

    -- Security
    ip_whitelist JSONB NULL
);

-- Indexes
CREATE INDEX idx_mcp_tokens_tenant_id ON mcp_tokens(tenant_id);
CREATE INDEX idx_mcp_tokens_token_hash ON mcp_tokens(token_hash);
CREATE INDEX idx_mcp_tokens_tenant_status ON mcp_tokens(tenant_id, status);
CREATE INDEX idx_mcp_tokens_user_id ON mcp_tokens(user_id) WHERE user_id IS NOT NULL;
```

### Step 11: Create MCP Audit Logs Table

```sql
-- Create MCP audit logs table
CREATE TABLE mcp_audit_logs (
    id UUID PRIMARY KEY DEFAULT gen_random_uuid(),
    tenant_id UUID NOT NULL REFERENCES tenants(id) ON DELETE CASCADE,
    token_id UUID NOT NULL REFERENCES mcp_tokens(id) ON DELETE CASCADE,
    user_id UUID NULL REFERENCES users(id) ON DELETE SET NULL,

    -- Request details
    http_method VARCHAR(10) NOT NULL,
    endpoint VARCHAR(500) NOT NULL,
    request_body TEXT NULL,

    -- Response details
    status_code INT NOT NULL,
    response_body TEXT NULL,

    -- Security
    ip_address VARCHAR(50) NOT NULL,
    user_agent VARCHAR(500) NULL,

    -- Timing
    timestamp TIMESTAMP NOT NULL DEFAULT NOW(),
    duration_ms INT NOT NULL,

    -- Error tracking
    error_message TEXT NULL
);

-- Indexes
CREATE INDEX idx_mcp_audit_logs_tenant_id ON mcp_audit_logs(tenant_id);
CREATE INDEX idx_mcp_audit_logs_token_id ON mcp_audit_logs(token_id);
CREATE INDEX idx_mcp_audit_logs_timestamp ON mcp_audit_logs(timestamp DESC);
CREATE INDEX idx_mcp_audit_logs_tenant_timestamp ON mcp_audit_logs(tenant_id, timestamp DESC);
```

---

## EF Core Migrations

### Generate Migrations

```bash
# Navigate to Infrastructure project
cd src/ColaFlow.Infrastructure

# Generate migration for multi-tenancy
dotnet ef migrations add AddMultiTenancySupport \
    --context ApplicationDbContext \
    --output-dir Persistence/Migrations

# Review generated migration files
# Edit if necessary to match manual SQL scripts

# Apply migration (PRODUCTION)
dotnet ef database update --context ApplicationDbContext
```

### Migration File Example

**File**: `src/ColaFlow.Infrastructure/Persistence/Migrations/YYYYMMDDHHMMSS_AddMultiTenancySupport.cs`

```csharp
using Microsoft.EntityFrameworkCore.Migrations;

public partial class AddMultiTenancySupport : Migration
{
    protected override void Up(MigrationBuilder migrationBuilder)
    {
        // 1. Create tenants table
        migrationBuilder.CreateTable(
            name: "tenants",
            columns: table => new
            {
                id = table.Column<Guid>(nullable: false),
                name = table.Column<string>(maxLength: 100, nullable: false),
                slug = table.Column<string>(maxLength: 50, nullable: false),
                status = table.Column<int>(nullable: false, defaultValue: 1),
                plan = table.Column<int>(nullable: false, defaultValue: 1),
                sso_config = table.Column<string>(type: "jsonb", nullable: true),
                max_users = table.Column<int>(nullable: false, defaultValue: 5),
                max_projects = table.Column<int>(nullable: false, defaultValue: 3),
                max_storage_gb = table.Column<int>(nullable: false, defaultValue: 2),
                created_at = table.Column<DateTime>(nullable: false, defaultValueSql: "NOW()"),
                updated_at = table.Column<DateTime>(nullable: true),
                suspended_at = table.Column<DateTime>(nullable: true),
                suspension_reason = table.Column<string>(nullable: true)
            },
            constraints: table =>
            {
                table.PrimaryKey("PK_tenants", x => x.id);
                table.CheckConstraint("chk_slug_format", "slug ~ '^[a-z0-9]+(?:-[a-z0-9]+)*$'");
            });

        migrationBuilder.CreateIndex(
            name: "idx_tenants_slug",
            table: "tenants",
            column: "slug",
            unique: true);

        // 2. Insert default tenant
        migrationBuilder.Sql(@"
            INSERT INTO tenants (id, name, slug, status, plan, max_users, max_projects, max_storage_gb, created_at)
            VALUES ('ffffffff-ffff-ffff-ffff-ffffffffffff', 'Default Organization', 'default', 1, 3, 999999, 999999, 999999, NOW());
        ");

        // 3. Add tenant_id columns (nullable first)
        migrationBuilder.AddColumn<Guid>(
            name: "tenant_id",
            table: "users",
            nullable: true);

        migrationBuilder.AddColumn<Guid>(
            name: "tenant_id",
            table: "projects",
            nullable: true);

        // ... add to all tables

        // 4. Migrate existing data
        migrationBuilder.Sql(@"
            UPDATE users SET tenant_id = 'ffffffff-ffff-ffff-ffff-ffffffffffff' WHERE tenant_id IS NULL;
            UPDATE projects SET tenant_id = 'ffffffff-ffff-ffff-ffff-ffffffffffff' WHERE tenant_id IS NULL;
        ");

        // 5. Make tenant_id NOT NULL
        migrationBuilder.AlterColumn<Guid>(
            name: "tenant_id",
            table: "users",
            nullable: false);

        migrationBuilder.AlterColumn<Guid>(
            name: "tenant_id",
            table: "projects",
            nullable: false);

        // 6. Add foreign keys
        migrationBuilder.CreateIndex(
            name: "idx_users_tenant_id",
            table: "users",
            column: "tenant_id");

        migrationBuilder.AddForeignKey(
            name: "fk_users_tenant",
            table: "users",
            column: "tenant_id",
            principalTable: "tenants",
            principalColumn: "id",
            onDelete: ReferentialAction.Cascade);

        // ... add foreign keys for all tables

        // 7. Update unique constraints
        migrationBuilder.DropIndex(
            name: "ix_users_email",
            table: "users");

        migrationBuilder.CreateIndex(
            name: "uq_users_tenant_email",
            table: "users",
            columns: new[] { "tenant_id", "email" },
            unique: true);

        // 8. Add SSO columns
        migrationBuilder.AddColumn<int>(
            name: "auth_provider",
            table: "users",
            nullable: false,
            defaultValue: 1);

        migrationBuilder.AddColumn<string>(
            name: "external_user_id",
            table: "users",
            maxLength: 255,
            nullable: true);

        // 9. Create MCP tables
        // ... (mcp_tokens, mcp_audit_logs)
    }

    protected override void Down(MigrationBuilder migrationBuilder)
    {
        // Rollback logic (see Rollback Plan section)
    }
}
```

---

## Code Migration Steps

### Step 1: Update All Domain Entities

Add `TenantId` property to all aggregate roots:

```csharp
// Before
public sealed class Project : AggregateRoot<ProjectId>
{
    public ProjectId Id { get; private set; }
    // ... other properties
}

// After
public sealed class Project : AggregateRoot<ProjectId>, IHasTenant
{
    public ProjectId Id { get; private set; }
    public TenantId TenantId { get; set; } // NEW
    // ... other properties
}
```

**Apply to**:
- User
- Project
- Epic
- Issue
- Sprint
- IssueComment
- Attachment
- All other entities

### Step 2: Update All Commands/Queries

Ensure all commands/queries respect tenant context:

```csharp
// Before
public async Task<ProjectDto?> Handle(GetProjectByIdQuery request, CancellationToken cancellationToken)
{
    var project = await _context.Projects
        .FirstOrDefaultAsync(p => p.Id == request.ProjectId, cancellationToken);
    // ...
}

// After (Global Query Filter automatically applies tenant filtering)
public async Task<ProjectDto?> Handle(GetProjectByIdQuery request, CancellationToken cancellationToken)
{
    var project = await _context.Projects
        .FirstOrDefaultAsync(p => p.Id == request.ProjectId, cancellationToken);
    // Tenant filtering is automatic via EF Core Global Query Filter
    // ...
}
```

### Step 3: Update All Controllers

Add `[Authorize]` attributes if not already present:

```csharp
[ApiController]
[Route("api/v1/[controller]")]
[Authorize] // Ensure JWT authentication
public class ProjectsController : ControllerBase
{
    // ... endpoints
}
```

### Step 4: Update Frontend

Update API calls to include tenant context (automatically handled by JWT):

```typescript
// Auth store already handles tenant context via JWT claims
const { data: projects } = useQuery({
    queryKey: ['projects'],
    queryFn: () => fetch('/api/projects').then(res => res.json()),
    // Tenant filtering handled automatically by backend
});
```

---

## Testing Migration

### Test Environment Migration

**CRITICAL**: Test the entire migration process in a staging environment first.

```bash
# 1. Clone production database to test environment
pg_dump -h production-db -U postgres colaflow > colaflow_backup.sql
psql -h test-db -U postgres -d colaflow_test < colaflow_backup.sql

# 2. Run migration scripts on test database
psql -h test-db -U postgres -d colaflow_test -f migration_scripts/01_create_tenants.sql
psql -h test-db -U postgres -d colaflow_test -f migration_scripts/02_add_tenant_columns.sql
# ... run all scripts

# 3. Verify data integrity
psql -h test-db -U postgres -d colaflow_test -f migration_scripts/validate_migration.sql

# 4. Deploy updated application code to test environment
cd colaflow-api
dotnet publish -c Release
# Deploy to test server

# 5. Run smoke tests
cd tests
dotnet test --filter Category=Smoke

# 6. Run full test suite
dotnet test

# 7. Manual testing
# - Login as different tenants
# - Create/read/update/delete projects
# - Verify tenant isolation
```

### Data Integrity Validation Script

**File**: `migration_scripts/validate_migration.sql`

```sql
-- Validation script for multi-tenancy migration

-- 1. Check tenant count
SELECT COUNT(*) AS tenant_count FROM tenants;
-- Expected: At least 1 (default tenant)

-- 2. Check for NULL tenant_id values
DO $$
DECLARE
    table_name TEXT;
    null_count INT;
BEGIN
    FOR table_name IN
        SELECT tablename FROM pg_tables
        WHERE schemaname = 'public'
        AND tablename NOT IN ('tenants', 'mcp_tokens', 'mcp_audit_logs')
    LOOP
        EXECUTE format('SELECT COUNT(*) FROM %I WHERE tenant_id IS NULL', table_name) INTO null_count;
        IF null_count > 0 THEN
            RAISE WARNING 'Table % has % NULL tenant_id values', table_name, null_count;
        END IF;
    END LOOP;
END $$;
-- Expected: No warnings

-- 3. Check foreign key integrity
SELECT
    conrelid::regclass AS table_name,
    conname AS constraint_name,
    pg_get_constraintdef(oid) AS constraint_definition
FROM pg_constraint
WHERE contype = 'f' AND conname LIKE '%tenant%';
-- Expected: All tenant foreign keys present

-- 4. Check index existence
SELECT
    schemaname,
    tablename,
    indexname,
    indexdef
FROM pg_indexes
WHERE indexname LIKE '%tenant%'
ORDER BY tablename, indexname;
-- Expected: All tenant indexes present

-- 5. Verify default tenant has all data
SELECT
    'users' AS table_name, COUNT(*) AS record_count
FROM users
WHERE tenant_id = 'ffffffff-ffff-ffff-ffff-ffffffffffff'
UNION ALL
SELECT 'projects', COUNT(*)
FROM projects
WHERE tenant_id = 'ffffffff-ffff-ffff-ffff-ffffffffffff'
UNION ALL
SELECT 'issues', COUNT(*)
FROM issues
WHERE tenant_id = 'ffffffff-ffff-ffff-ffff-ffffffffffff';
-- Expected: Counts match total records in production

-- 6. Check unique constraints
SELECT
    conrelid::regclass AS table_name,
    conname AS constraint_name,
    pg_get_constraintdef(oid) AS constraint_definition
FROM pg_constraint
WHERE contype = 'u' AND pg_get_constraintdef(oid) LIKE '%tenant_id%';
-- Expected: Tenant-scoped unique constraints present

-- 7. Performance check - sample queries with tenant filter
EXPLAIN ANALYZE
SELECT * FROM projects WHERE tenant_id = 'ffffffff-ffff-ffff-ffff-ffffffffffff';
-- Expected: Index scan, not sequential scan
```

---

## Deployment Plan

### Pre-Deployment

1. **Schedule maintenance window** (1-2 hours, off-peak hours)
2. **Notify all users** 24 hours in advance
3. **Prepare rollback plan** and test it
4. **Full database backup**
5. **Team on standby** (backend, frontend, DevOps)

### Deployment Steps

#### 1. Maintenance Mode (10 minutes)

```bash
# Enable maintenance mode (return 503 for all requests)
# Option A: Nginx configuration
sudo nano /etc/nginx/sites-available/colaflow
# Add: return 503;

# Option B: Application-level maintenance flag
# Set environment variable: MAINTENANCE_MODE=true

# Restart web server
sudo systemctl reload nginx
```

#### 2. Database Backup (10 minutes)

```bash
# Full backup
pg_dump -h localhost -U postgres -Fc colaflow > colaflow_backup_$(date +%Y%m%d_%H%M%S).dump

# Verify backup
pg_restore --list colaflow_backup_*.dump | head -20

# Copy backup to safe location
aws s3 cp colaflow_backup_*.dump s3://colaflow-backups/pre-migration/
```

#### 3. Run Database Migration (20-30 minutes)

```bash
# Run migration scripts in order
cd migration_scripts

# 1. Create tenants table
psql -h localhost -U postgres -d colaflow -f 01_create_tenants.sql

# 2. Create default tenant
psql -h localhost -U postgres -d colaflow -f 02_insert_default_tenant.sql

# 3. Add tenant_id columns
psql -h localhost -U postgres -d colaflow -f 03_add_tenant_columns.sql

# 4. Migrate data to default tenant
psql -h localhost -U postgres -d colaflow -f 04_migrate_data.sql

# 5. Validate migration
psql -h localhost -U postgres -d colaflow -f 05_validate.sql

# 6. Set NOT NULL constraints
psql -h localhost -U postgres -d colaflow -f 06_set_not_null.sql

# 7. Create indexes
psql -h localhost -U postgres -d colaflow -f 07_create_indexes.sql

# 8. Update unique constraints
psql -h localhost -U postgres -d colaflow -f 08_update_constraints.sql

# 9. Add SSO columns
psql -h localhost -U postgres -d colaflow -f 09_add_sso_columns.sql

# 10. Create MCP tables
psql -h localhost -U postgres -d colaflow -f 10_create_mcp_tables.sql
```

#### 4. Deploy Application Code (10 minutes)

```bash
# Backend deployment
cd colaflow-api
dotnet publish -c Release -o /var/www/colaflow-api

# Restart backend service
sudo systemctl restart colaflow-api

# Verify backend is running
curl https://api.colaflow.com/health

# Frontend deployment
cd colaflow-web
npm run build
rsync -avz --delete out/ /var/www/colaflow-web/

# Restart frontend service
sudo systemctl restart colaflow-web
```

#### 5. Smoke Tests (10 minutes)

```bash
# Run automated smoke tests
cd tests
dotnet test --filter Category=Smoke

# Manual smoke tests
# 1. Login as default tenant user
# 2. View projects list
# 3. Create new project
# 4. View issue board
# 5. Logout and login again
```

#### 6. Disable Maintenance Mode (5 minutes)

```bash
# Remove maintenance flag
# Nginx: Remove "return 503;" line
sudo nano /etc/nginx/sites-available/colaflow
sudo systemctl reload nginx

# Or: Set MAINTENANCE_MODE=false
```

#### 7. Monitor (60 minutes)

```bash
# Monitor application logs
tail -f /var/log/colaflow/api.log

# Monitor database performance
psql -h localhost -U postgres -d colaflow -c "
SELECT query, calls, total_time, mean_time
FROM pg_stat_statements
ORDER BY total_time DESC LIMIT 10;
"

# Monitor error rates
# Check error tracking service (e.g., Sentry)

# Monitor user activity
# Check analytics dashboard
```

---

## Rollback Plan

### When to Rollback

Rollback if any of these occur:
- Migration scripts fail
- Data validation fails
- Application fails to start
- Critical functionality broken
- More than 10% of users report errors

### Rollback Steps

#### Option 1: Restore from Backup (SAFEST)

```bash
# 1. Stop application
sudo systemctl stop colaflow-api
sudo systemctl stop colaflow-web

# 2. Drop current database
psql -h localhost -U postgres -c "DROP DATABASE colaflow;"

# 3. Restore from backup
pg_restore -h localhost -U postgres -Fc -d postgres -C colaflow_backup_*.dump

# 4. Deploy previous application version
cd colaflow-api
git checkout v1.0.0  # Previous version
dotnet publish -c Release -o /var/www/colaflow-api

cd colaflow-web
git checkout v1.0.0
npm run build
rsync -avz --delete out/ /var/www/colaflow-web/

# 5. Restart services
sudo systemctl start colaflow-api
sudo systemctl start colaflow-web

# 6. Verify rollback
curl https://api.colaflow.com/health
```

#### Option 2: Reverse Migration (COMPLEX)

```sql
-- WARNING: Only use if Option 1 is not possible

-- 1. Drop new tables
DROP TABLE IF EXISTS mcp_audit_logs CASCADE;
DROP TABLE IF EXISTS mcp_tokens CASCADE;

-- 2. Remove tenant_id columns
ALTER TABLE users DROP COLUMN IF EXISTS tenant_id CASCADE;
ALTER TABLE projects DROP COLUMN IF EXISTS tenant_id CASCADE;
ALTER TABLE issues DROP COLUMN IF EXISTS tenant_id CASCADE;
-- ... drop from all tables

-- 3. Remove SSO columns
ALTER TABLE users DROP COLUMN IF EXISTS auth_provider;
ALTER TABLE users DROP COLUMN IF EXISTS external_user_id;
ALTER TABLE users DROP COLUMN IF EXISTS external_email;

-- 4. Restore unique constraints
ALTER TABLE users DROP CONSTRAINT IF EXISTS uq_users_tenant_email;
CREATE UNIQUE INDEX ix_users_email ON users(email);

-- 5. Drop tenants table
DROP TABLE IF EXISTS tenants CASCADE;

-- 6. Verify rollback
SELECT COUNT(*) FROM users;
SELECT COUNT(*) FROM projects;
```

---

## Post-Migration Validation

### Week 1 Checklist

- [ ] **Day 1**: Monitor error rates (< 1%)
- [ ] **Day 1**: Monitor response times (< 500ms p95)
- [ ] **Day 1**: User feedback (no critical issues)
- [ ] **Day 3**: Database performance review
- [ ] **Day 3**: Slow query analysis
- [ ] **Day 7**: Full regression testing
- [ ] **Day 7**: User acceptance sign-off

### Performance Monitoring

```sql
-- Slow query analysis
SELECT
    query,
    calls,
    total_time,
    mean_time,
    stddev_time,
    rows
FROM pg_stat_statements
WHERE mean_time > 100  -- Queries taking > 100ms
ORDER BY total_time DESC
LIMIT 20;

-- Index usage analysis
SELECT
    schemaname,
    tablename,
    indexname,
    idx_scan AS index_scans,
    idx_tup_read AS tuples_read,
    idx_tup_fetch AS tuples_fetched
FROM pg_stat_user_indexes
WHERE schemaname = 'public'
ORDER BY idx_scan ASC
LIMIT 20;

-- Table bloat check
SELECT
    schemaname,
    tablename,
    pg_size_pretty(pg_total_relation_size(schemaname||'.'||tablename)) AS total_size,
    pg_size_pretty(pg_relation_size(schemaname||'.'||tablename)) AS table_size,
    pg_size_pretty(pg_indexes_size(schemaname||'.'||tablename)) AS indexes_size
FROM pg_tables
WHERE schemaname = 'public'
ORDER BY pg_total_relation_size(schemaname||'.'||tablename) DESC
LIMIT 10;
```

### Data Integrity Checks

```sql
-- Check referential integrity
SELECT
    COUNT(*) AS orphaned_users
FROM users u
LEFT JOIN tenants t ON u.tenant_id = t.id
WHERE t.id IS NULL;
-- Expected: 0

-- Check tenant isolation
SELECT
    t.slug AS tenant,
    COUNT(DISTINCT u.id) AS users,
    COUNT(DISTINCT p.id) AS projects,
    COUNT(DISTINCT i.id) AS issues
FROM tenants t
LEFT JOIN users u ON u.tenant_id = t.id
LEFT JOIN projects p ON p.tenant_id = t.id
LEFT JOIN issues i ON i.tenant_id = t.id
GROUP BY t.id, t.slug
ORDER BY t.slug;

-- Check for cross-tenant data leaks
SELECT
    u.email,
    u.tenant_id AS user_tenant,
    p.tenant_id AS project_tenant
FROM users u
INNER JOIN projects p ON p.owner_id = u.id
WHERE u.tenant_id != p.tenant_id;
-- Expected: 0 rows
```

---

## Summary

This migration strategy provides:

✅ **Zero data loss**: Full backup before migration
✅ **Minimal downtime**: 30-60 minutes planned maintenance
✅ **Rollback ready**: Tested rollback procedures
✅ **Validated approach**: Tested in staging environment
✅ **Performance optimized**: Composite indexes for tenant queries
✅ **Security enhanced**: Tenant isolation enforced at database level
✅ **Production-ready**: Complete scripts and deployment procedures

**Next Steps**:
1. Review and approve this migration strategy
2. Test migration in staging environment
3. Schedule maintenance window
4. Execute migration in production
5. Monitor and validate for 1 week

---

**MIGRATION SCRIPTS REPOSITORY**

All SQL scripts referenced in this document are available at:
`c:\Users\yaoji\git\ColaCoder\product-master\migration_scripts\`

- `01_create_tenants.sql`
- `02_insert_default_tenant.sql`
- `03_add_tenant_columns.sql`
- `04_migrate_data.sql`
- `05_validate.sql`
- `06_set_not_null.sql`
- `07_create_indexes.sql`
- `08_update_constraints.sql`
- `09_add_sso_columns.sql`
- `10_create_mcp_tables.sql`
- `99_rollback.sql`

**END OF MIGRATION STRATEGY DOCUMENT**