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| db_watch | revori | |
|---|---|---|
| 1 | 1 | |
| 0 | 10 | |
| - | - | |
| 0.0 | 0.0 | |
| about 3 years ago | over 9 years ago | |
| JavaScript | Java | |
| MIT License | GNU General Public License v3.0 or later |
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db_watch
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Ask HN: Is there a way to subscribe to an SQL query for changes?
It's certainly not production situation, but I quickly made this [1] a while back to help with "watching" certain queries for debugging. It uses a polling approach.
[1] https://github.com/grouparoo/db_watch
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It's no longer maintained, unfortunately.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
What are some alternatives?
rethinkdb_rebirth - The open-source database for the realtime web.
integrate - Core IntegrateDB source code repository.
cainophile
pg-live-select - Live Updating PostgreSQL SELECT statements
flow - 🌊 Continuously synchronize the systems where your data lives, to the systems where you _want_ it to live, with Estuary Flow. 🌊
PipelineDB - High-performance time-series aggregation for PostgreSQL
timely-dataflow - A modular implementation of timely dataflow in Rust