Seeding Patterns

Flash ORM's seeding system automatically generates realistic fake data. This page shows patterns for common scenarios.

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Basic Seeding

Seed All Tables

# Default: 10 records per table
flash seed

# Custom count for all tables
flash seed --count 100

# Truncate and reseed
flash seed --truncate --count 50

Seed Specific Tables

# Seed only users and posts
flash seed users posts

# Seed with different counts
flash seed users:50 posts:200 comments:1000

# Exclude tables you don't want seeded
flash seed --exclude logs,audit_logs,sessions

Dry Run (Preview)

# See what would be generated without inserting
flash seed --dry-run

# Preview specific tables
flash seed users:5 posts:10 --dry-run

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Realistic Data Distribution

Blog Platform

# Seed users first (authors and readers)
flash seed users:20

# Then seed content
flash seed categories:5 tags:30 posts:100 comments:500

# Or all at once (Flash handles order automatically)
flash seed users:20 categories:5 tags:30 posts:100 comments:500

E-Commerce

# Product catalog
flash seed categories:10 products:500

# With customer activity
flash seed users:1000 products:500 orders:5000 order_items:15000 reviews:2000

Social Media

# Network effect data
flash seed users:100 posts:500 comments:2000 likes:10000 follows:2000

SaaS/Multi-Tenant

# Tenant structure
flash seed tenants:5 users:50 projects:100 tasks:500

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Automated Column Generation

Flash automatically generates data based on column names and types:

Identity Columns

Column Name	Generated Value
email, user_email	john.doe1@gmail.com
username, login	john_doe_1
first_name, fname	John
last_name, lname	Doe
password, pwd	aB3$kL9mPqR2
name	John Doe

Content Columns

Column Name	Generated Value
title, headline	Getting Started with Go Programming
content, body	Lorem ipsum paragraph
bio, about	Short biography paragraph
description, summary	Sample description paragraph
slug, permalink	getting-started-42
phone, tel	+1-234-567-8901

Location Columns

Column Name	Generated Value
address, addr	123 Main Street, New York, NY 12345
city	New York
state, province	California
zip, postal	12345
country	US
latitude, lat	40.7128
longitude, lng	-74.0060

Technical Columns

Column Name	Generated Value
ip_address, ip	192.168.1.1
color, hex	#3f7a9c
token, api_key	a1b2c3d4e5f6... (hex)
hash, checksum	a1b2c3d4... (hex)
metadata, meta	{"generated": true}
locale, lang	en
currency	USD

Business Columns

Column Name	Generated Value
company, organization	Tech Solutions Inc
product	Premium Subscription
status	active
category	Technology
priority	medium
role	user
gender	male
tag, label	technology

Numeric Columns

Column Name	Generated Value
price, amount	$1,234.56
quantity, qty	1-1000
rating, score	1-5
percent, percentage	0-100%
progress	0-100
sort_order	0-999
age	18-97
version	2.14.3

Boolean Columns

Boolean prefixes are automatically detected:

Column Name	Generated Value
is_active	true/false
is_verified	true/false
has_permission	true/false
can_edit	true/false
is_published, published	true/false
is_featured, featured	true/false
deleted, archived, locked	true/false

Temporal Columns

Coordinated timestamps: when both created_at and updated_at exist, updated_at is always >= created_at.

Column Name	Generated Value
created_at	Past date (up to 1 year ago)
updated_at	Between created_at and now
published_at	Past date
dob, birth_date	18-78 years ago
duration	1-3600 seconds

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SQL Type Handling

Flash handles all common SQL types:

SQL Type	Generated Value
INTEGER, INT	1-1,000,000
BIGINT	int64 value
SMALLINT	1-32,767
TINYINT	1-127
SERIAL	Auto-increment (skipped)
VARCHAR, TEXT	Random sentence
CHAR	6-char code
BOOLEAN, BOOL	true/false
TIMESTAMP, DATETIME	Past date
TIMESTAMPTZ	Past date with timezone
DATE	Past date (time.Time)
TIME	HH:MM:SS
DECIMAL, NUMERIC	$0-$10,000
FLOAT, REAL, DOUBLE	Float value
UUID	RFC 4122 v4 UUID
JSON, JSONB	{"generated": true}
BYTEA, BLOB	Binary data
ARRAY	{item1,item2,item3}
ENUM('a','b')	Random enum value

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CI/CD Integration

Test Database Setup

#!/bin/bash
# scripts/setup-test-db.sh

set -e

export DATABASE_URL="postgres://test:test@localhost:5432/test_db"

# Reset and setup
flash reset --force
flash apply --force
flash seed --count 25 --force

echo "Test database ready!"

GitHub Actions

# .github/workflows/test.yml
name: Tests

jobs:
  test:
    runs-on: ubuntu-latest
    services:
      postgres:
        image: postgres:16
        env:
          POSTGRES_PASSWORD: test
        options: >-
          --health-cmd pg_isready
          --health-interval 10s
          --health-timeout 5s
          --health-retries 5

    steps:
      - uses: actions/checkout@v4
      - name: Setup Flash ORM
        run: |
          go install github.com/Lumos-Labs-HQ/flash@latest
          flash init --postgresql
      - name: Setup Database
        run: |
          flash apply --force
          flash seed --count 10 --force
      - name: Run Tests
        run: go test ./...

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Common Workflows

Fresh Development Environment

# Complete reset and seed
flash reset --force
flash apply
flash seed --count 50
flash studio

Adding Test Data After Schema Change

# Migrate, then seed new tables
flash migrate "add reviews table"
flash apply
flash seed reviews:100

Performance Testing

# Large dataset for load testing
flash seed --count 10000 --force

# Specific distribution
flash seed users:10000 posts:50000 comments:200000 --force

Demo Environment

# Just enough data to look realistic
flash seed --truncate --count 25