Show HN: DDL to Data – Generate realistic test data from SQL schemas • Hacker News Board

Show HN: DDL to Data – Generate realistic test data from SQL schemas

#1

Post by tbrannan » Tue, Jan 06, 2026, 12:47 PM UTC

I built DDL to Data after repeatedly pushing back on "just use production data and mask it" requests. Teams needed populated databases for testing, but pulling prod meant security reviews, PII scrubbing, and DevOps tickets. Hand-written seed scripts were the alternative slow, fragile, and out of sync the moment schemas changed.

Paste your CREATE TABLE statements, get realistic test data back. It parses your schema, preserves foreign key relationships, and generates data that looks real, emails look like emails, timestamps are reasonable, uniqueness constraints are honored.

No setup, no config. Works with PostgreSQL and MySQL.

https://ddltodata.com

Would love feedback from anyone who deals with test data or staging environments. What's missing?

Re: Show HN: DDL to Data – Generate realistic test data from SQL schemas

#2

Post by ForHackernews » Tue, Jan 06, 2026, 1:53 PM UTC

This is a great idea. I've thought about doing something similar! On the other hand, I'm not sure it's a business. Is this using AI?

The pricing seems extremely high for what's basically a call to https://github.com/faker-ruby/faker but that makes sense if it has to pay for OpenAI tokens.

(who knows though, plenty of B2B deals signed for sillier things than this - good luck, OP)

Re: Show HN: DDL to Data – Generate realistic test data from SQL schemas

#3

Post by Omnipresent » Tue, Jan 06, 2026, 1:56 PM UTC

how is this compared to https://shadowtraffic.io/

Re: Show HN: DDL to Data – Generate realistic test data from SQL schemas

#4

Post by tbrannan » Tue, Jan 06, 2026, 1:58 PM UTC

ForHackernews wrote: post #2

This is a great idea. I've thought about doing something similar! On the other hand, I'm not sure it's a business. Is this using AI? The pricing seems extremely high for what's basically a call to https://github.com/faker-ruby/faker but that makes sense if it has to pay for OpenAI tokens. (who knows though, plenty of B2B deals signed for sillier things than this - good luck, OP)

Thanks! To clarify, the core engine isn't AI. It's deterministic pattern matching, so it runs in milliseconds with no token costs. There's an optional "Story Mode" that uses AI for narrative-coherent data (like "a churning SaaS with seasonal trends"), but the base product is just schema parsing + smart type inference.

The difference from Faker: you don't write any code. Paste your CREATE TABLE, get data back. Faker is a library you have to integrate, configure field-by-field, and maintain as your schema changes. Different use case — more like "I need a seeded database in 30 seconds" vs "I'm building a test suite."

Fair point on pricing though, still figuring that out. Appreciate the feedback.

Re: Show HN: DDL to Data – Generate realistic test data from SQL schemas

#5

Post by james_marks » Tue, Jan 06, 2026, 2:11 PM UTC

Congrats on being launchable!

I've written seed data scripts a number of times, so I get the need. How do you think about creating larger amounts of data?

E.g., I'm building a statistical product where the seed data needs to be 1M rows; performance differences between implementations start to matter.

Re: Show HN: DDL to Data – Generate realistic test data from SQL schemas

#6

Post by tbrannan » Tue, Jan 06, 2026, 2:20 PM UTC

james_marks wrote: post #5

Congrats on being launchable! I've written seed data scripts a number of times, so I get the need. How do you think about creating larger amounts of data? E.g., I'm building a statistical product where the seed data needs to be 1M rows; performance differences between implementations start to matter.

Thanks! At 1M rows, I think a few things matter:

Streaming: Can't hold it all in memory. Generate in chunks, write, release, repeat.

Format choice: Parquet with row groups is fast and compresses well. SQL needs batched inserts (~1000/statement). Direct DB writes via COPY skip serialization entirely is usually fastest.

FK relationships: The real bottleneck. Pre-generate parent PKs, hold in memory, reference for children. Gets tricky with complex graphs at scale.

Parallelization: Row generation is embarrassingly parallel, but writes are serial. Chunk-then-merge is on our radar but not shipped yet.

What does your stat product need, realistic distributions or pure volume/stress testing?

Re: Show HN: DDL to Data – Generate realistic test data from SQL schemas

#7

Post by fcoury » Tue, Jan 06, 2026, 2:34 PM UTC

A while ago I worked on a similar idea, it was back when I was learning Rust so not super proud of the code, but I love the name of the tool: https://github.com/gistia/joindoe

Re: Show HN: DDL to Data – Generate realistic test data from SQL schemas

#8

Post by bdcravens » Tue, Jan 06, 2026, 2:56 PM UTC

I appreciate this product existing, but the row limits in each tier seem very constrained.

Re: Show HN: DDL to Data – Generate realistic test data from SQL schemas

#9

Post by tbrannan » Tue, Jan 06, 2026, 2:59 PM UTC

bdcravens wrote: post #8

I appreciate this product existing, but the row limits in each tier seem very constrained.

Thanks for the feedback! Honestly, we're still dialing in the tiers, what row limits would feel reasonable to you for your use case? Always helpful to hear what people actually need.

Re: Show HN: DDL to Data – Generate realistic test data from SQL schemas

#10

Post by ljm » Tue, Jan 06, 2026, 3:01 PM UTC

Reminds me a bit of Snaplet before it embarked on its incredible journey to get acquired by Supabase and shut down.

I like the concept but the painpoint has never been around creating realistic looking emails and such like, but creating data that is realistic in terms of the business domain and in terms of volume.