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Instant database clones with PostgreSQL 18

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Re: Instant database clones with PostgreSQL 18

#51

Post by rootnod3 »

pritambarhate wrote: post #38
teiferer wrote: post #21

Earlier quoted context omitted.

You mean you told Claude a bunch of details and it built it for you? Mind you, I'm not saying it's bad per se. But shouldn't we be open and honest about this? I wonder if this is the new normal. Somebody says "I built Xyz" but then you realize it's vibe coded.

Let's say there is an architect and he also owns a construction company. This architect, then designs a building and gets it built from of his employees and contractors. In such cases the person says, I have built this building. People who found companies, say they have built companies. It's commonly accepted in our society. So even if Claude built for it for GP, as long as GP designed it, paid for tools (Claude) to…

That has to be the worst analogy I have read in a while, and I’m HN that says something.

Re: Instant database clones with PostgreSQL 18

#52

Post by chamomeal »

radarroark wrote: post #12

In theory, a database that uses immutable data structures (the hash array mapped trie popularized by Clojure) could allow instant clones on any filesystem, not just ZFS/XFS, and allow instant clones of any subset of the data, not just the entire db. I say "in theory" but I actually built this already so it's not just a theory. I never understood why there aren't more HAMT based databases.

Does datomic have built in cloning functionality? I’ve been wanting to try datomic out but haven’t felt like putting in the work to make a real app lol

Re: Instant database clones with PostgreSQL 18

#53

Post by earthnail »

dpedu wrote: post #35
earthnail wrote: post #25

Earlier quoted context omitted.

Not sure why this is downvoted. For a critical tool like DB cloning, I‘d very much appreciate if it was hand written. Simply because it means it’s also hand reviewed at least once (by definition). We wouldn’t have called it reviewed in the old world, but in the AI coding world we’re now in it makes me realise that yes, it is a form of reviewing. I use Claude a lot btw. But I wouldn’t trust it on mission critical stuf…

It's being downvoted because the commenter is asking for something that is already in the readme. Furthermore, it's ironic that the person raising such an issue is performing the same mistake as they are calling out - neglecting to read something they didn't write.

It‘s at the very bottom of the readme, below the MIT license mention. Yes, it’s there, but very much in the fineprint. I think the easier thing to spot is the CLAUDE.md in the code (and in particular how comprehensive it is).

Again, I love Claude, I use it a ton, but a topic like database cloning requires a certain rigour in my opinion. This repo does not seem to have it. If I had hired a consultant to build a tool like this and would receive this amount of vibe coding, I’d feel deceived. I wouldn’t trust it on my critical data.

Re: Instant database clones with PostgreSQL 18

#54

Post by peterldowns »

Really interesting article, I didn't know that the template cloning strategy was configurable. Huge fan of template cloning in general; I've used Neon to do it for "live" integration environments, and I have a golang project https://github.com/peterldowns/pgtestdb that uses templates to give you ~unit-test-speed integration tests that each get their own fully-schema-migrated Postgres database.

Back in the day (2013?) I worked at a startup where the resident Linux guru had set up "instant" staging environment databases with btrfs. Really cool to see the same idea show up over and over with slightly different implementations. Speed and ease of cloning/testing is a real advantage for Postgres and Sqlite, I wish it were possible to do similar things with Clickhouse, Mysql, etc.

Re: Instant database clones with PostgreSQL 18

#55

Post by 6r17 »

teiferer wrote: post #21
elitan wrote: post #17

For those who can't wait for PG18 or need full instance isolation: I built Velo, which does instant branching using ZFS snapshots instead of reflinks. Works with any PG version today. Each branch is a fully isolated PostgreSQL container with its own port. ~2-5 seconds for a 100GB database. https://github.com/elitan/velo Main difference from PG18's approach: you get complete server isolation (useful for testing migrat…

You mean you told Claude a bunch of details and it built it for you? Mind you, I'm not saying it's bad per se. But shouldn't we be open and honest about this? I wonder if this is the new normal. Somebody says "I built Xyz" but then you realize it's vibe coded.

There was a recent wave of such comment on the rust subreddit - exactly in this shape "Oh you mean you built this with AI". This is highly toxic, lead to no discussion, and is literally drove by some dark thought from the commentator. I really hope HN will not jump on this bandwagon and will focus instead on creating cool stuff.

Everybody in the industry is vibecoding right now - the things that stick are due to sufficient quality being pushed on it. Having a pessimistic / judgmental surface reaction to everything as being "ai slop" is not something that I'm going to look forward in my behavior.

Re: Instant database clones with PostgreSQL 18

#56

Post by fauigerzigerk »

pritambarhate wrote: post #38
teiferer wrote: post #21

Earlier quoted context omitted.

You mean you told Claude a bunch of details and it built it for you? Mind you, I'm not saying it's bad per se. But shouldn't we be open and honest about this? I wonder if this is the new normal. Somebody says "I built Xyz" but then you realize it's vibe coded.

Let's say there is an architect and he also owns a construction company. This architect, then designs a building and gets it built from of his employees and contractors. In such cases the person says, I have built this building. People who found companies, say they have built companies. It's commonly accepted in our society. So even if Claude built for it for GP, as long as GP designed it, paid for tools (Claude) to…

I agree that it's ultimately about the product.

But here's the problem. Five years ago, when someone on here said, "I wrote this non-trivial software", the implication was that a highly motivated and competent software engineer put a lot of effort into making sure that the project meets a reasonable standard of quality and will probably put some effort into maintaining the project.

Today, it does not necessarily imply that. We just don't know.

Re: Instant database clones with PostgreSQL 18

#57

Post by peterldowns »

BenjaminFaal wrote: post #9

For anyone looking for a simple GUI for local testing/development of Postgres based applications. I built a tool a few years ago that simplifies the process: https://github.com/BenjaminFaal/pgtt

Is this basically using templates as "snapshots", and making it easy to go back and forth between them? Little hard to tell from the README but something like that would be useful to me and my team: right now it's a pain to iterate on sql migrations, and I think this would help.

Re: Instant database clones with PostgreSQL 18

#58

Post by peterldowns »

francislavoie wrote: post #50
renewiltord wrote: post #46

Earlier quoted context omitted.

I have not done this so it’s theorycrafting but can’t you do the following? 1. Have a local data dir with initial state 2. Create an overlayfs with a temporary directory 3. Launch your job in your docker container with the overlayfs bind mount as your data directory 4. That’s it. Writes go to the overlay and the base directory is untouched

But how does the reset happen fast, the problem isn't with preventing permanent writes or w/e, it's with actually resetting for the next test. Also using overlayfs will immediately be slower at runtime than tmpfs which we're already doing.

Yeah unfortunately I think that it's not really possible to hit the speed of a TEMPLATE copy with MariaDB. @EvanElias (maintainer of https://github.com/skeema/skeema about this) was looking into it at one point, might consider reaching out to him — he's the foremost mysql expert that I know.

Re: Instant database clones with PostgreSQL 18

#59

Post by peterldowns »

gavinray wrote: post #33
oulipo2 wrote: post #22

Assuming I'd like to replicate my production database for either staging, or to test migrations, etc, and that most of my data is either: - business entities (users, projects, etc) - and "event data" (sent by devices, etc) where most of the database size is in the latter category, and that I'm fine with "subsetting" those (eg getting only the last month's "event data") what would be the best strategy to create a kind…

You can use "psql" to dump subsets of data from tables and then later import them. Something like: psql -c "\copy (SELECT * FROM event_data ORDER BY created_at DESC LIMIT 100) TO 'event-data-sample.csv' WITH CSV HEADER" https://www.postgresql.org/docs/current/sql-copy.html It'd be really nice if pg_dump had a "data sample"/"data subset" option but unfortunately nothing like that is built in that I know of.

pg_dump has a few annoyances when it comes to doing stuff like this — tricky to select exactly the data/columns you want, and also the dumped format is not always stable. My migration tool pgmigrate has an experimental `pgmigrate dump` subcommand for doing things like this, might be useful to you or OP maybe even just as a reference. The docs are incomplete since this feature is still experimental, file an issue if you have any questions or trouble

https://github.com/peterldowns/pgmigrate

Re: Instant database clones with PostgreSQL 18

#60

Post by stronglikedan »

renewiltord wrote: post #43
dpedu wrote: post #32

Earlier quoted context omitted.

Huh? It says so right in the README. https://github.com/elitan/velo/blame/12712e26b18d0935bfb6c6e... And are we really doing this? Do we need to admit how every line of code was produced? Why? Are you expecting to see "built with the influence of Stackoverflow answers" or "google searches" on every single piece of software ever? It's an exercise of pointlessness.

I think you need to start with the following statement: > We would like to acknowledge the open source people, who are the traditional custodians of this code. We pay our respects to the stack overflow elders, past, present, and future, who call this place, the code and libraries that $program sits upon, their work. We are proud to continue their tradition of coming together and growing as a community. We thank the s…

> a Brazilian invented the airplane

lol, good one!

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