revori
realtime
revori | realtime | |
---|---|---|
1 | 54 | |
10 | 6,470 | |
- | 0.8% | |
0.0 | 9.2 | |
over 9 years ago | 11 days ago | |
Java | Elixir | |
GNU General Public License v3.0 or later | Apache License 2.0 |
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revori
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Ask HN: Is there a way to subscribe to an SQL query for changes?
I've implemented a RDBMS that supports this [1]. It handles joins, views (which are automatically materialized and incrementally updated), etc. It's memory only, and it doesn't support exotic stuff like recursive CTEs, but it does exactly what you're asking for. We used it in production successfully for frequently-updated real time data at the company where I used to work.
Notably, it uses persistent search trees such that each revision shares structure with the previous one, which makes diffing two closely-related revisions extremely efficient (just skip over any shared structure). Subscribers just receive a stream of diffs, with backpressure handled automatically by skipping over intermediate revisions. See [2] for a more detailed summary.
It also exposes revisions as first-class objects, which allows you to tag and diff them. Specifically, you can run arbitrary queries on both revisions and diffs. See [3] for examples.
It's no longer maintained, unfortunately. Someday I may revive it, perhaps adding support for spilling data that won't fit in memory to log-structured merge trees. I'd also rewrite it in a language like Rust, which will help flatten some of the more pointer-heavy data structures and reduce tail latencies. If anyone is interested in seeing that happen or helping out, let me know.
I'm really surprised this still isn't supported in mainstream DBMSes. The MVCC model in PostgreSQL seems particularly well suited to it.
[1]: https://github.com/ReadyTalk/revori
realtime
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A Technical Dive into PostgreSQL's replication mechanisms
You can LISTEN/NOTIFY. Or you can use logical replication and a custom subscriber.[1] Supabase uses the latter.[2]
[1]: https://www.postgresql.org/docs/current/logical-replication....
[2]: https://github.com/supabase/realtime
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Supabase Studio: AI Assistant and User Impersonation
Supabase Realtime is great for building collaborative applications. You can receive database changes over websockets, store and synchronize data about user presence, and broadcast any data to clients via "channels".
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Unpacking Elixir: Observability
We use :telemetry to collect usage data per tenant for Supabase Realtime.
We do this for rate limiting but it also makes it very easy for us to attach a listener (https://github.com/supabase/realtime/blob/main/lib/realtime/...) which ships these (per second) aggregates to BigQuery (via Logflare), which then the billing team can aggregate further to display and actually bill people with.
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All the ways to capture changes in Postgres
Yo :D This is what Supabase Realtime does!
https://github.com/supabase/realtime
Spin up a Supabase database and then subscribe to changes with WebSockets.
You can play with it here once you have a db: https://realtime.supabase.com/inspector/new
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Supabase Local Dev: migrations, branching, and observability
Every project is a Postgres database, wrapped in a suite of tools like Auth, Storage, Edge Functions, Realtime and Vectors, and encompassed by API middleware and logs.
- Sync client state globally over WebSockets in Realtime
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Writing a chat application in Django 4.2 using async StreamingHttpResponse
Where can I learn more about this? I've been thinking of trying to integrate Supabase Realtime (https://github.com/supabase/realtime) into my Django app (without the rest of Supabase), but I'd also like to keep things even simpler if possible.
Also, what was the reason not to go with Gevent?
- Supabase Realtime – Broadcast, Presence, and Postgres Changes via WebSockets
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How to Listen to Database Changes Using Postgres Triggers in Elixir
I believe #2 was the main driver for the supabase team to build their real-time component: https://github.com/supabase/realtime
Background/announcement: https://supabase.com/blog/supabase-realtime-multiplayer-gene...
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How To Kill A Fly With A Shotgun
As a minor note, one of the linked articles talks about having used RethinkDB for its changefeeds and I made a mental note a bit back that if I ever want that supabase's realtime ( https://github.com/supabase/realtime ) provides something rather like that atop Postgres and I should try that before doing anything clever.
What are some alternatives?
rethinkdb_rebirth - The open-source database for the realtime web.
supabase - The open source Firebase alternative.
cainophile
debezium - Change data capture for a variety of databases. Please log issues at https://issues.redhat.com/browse/DBZ.
pg-live-select - Live Updating PostgreSQL SELECT statements
blockscout - Blockchain explorer for Ethereum based network and a tool for inspecting and analyzing EVM based blockchains.
PipelineDB - High-performance time-series aggregation for PostgreSQL
Appwrite - Your backend, minus the hassle.
flow - 🌊 Continuously synchronize the systems where your data lives, to the systems where you _want_ it to live, with Estuary Flow. 🌊
litestream - Streaming replication for SQLite.
timely-dataflow - A modular implementation of timely dataflow in Rust
Hasura - Blazing fast, instant realtime GraphQL APIs on your DB with fine grained access control, also trigger webhooks on database events.