On Mon, Jul 03, 2023 at 08:33:32PM +0200, Hannu Krosing wrote: > One thing that was briefly mentioned (but is missing from the notes) > is need to have a sample API client in contrib/ , both for having a > 2nd user for API to make it more likely that non-heap AMs are doable > and also to serve as an easy starting point for someone interested in > developing a new AM.
That sounds like a fair thing to have, though templates may live better under src/test/modules. > There are a few candidates which could be lightweight enough for this > > * in-memory temp tables, especially if you specify max table size at > creation and/or limit data types which can be used. > > * "overlay tables" - tables which "overlay" another - possibly > read-only - table and store only changed rows and tombstones for > deletions. (this likely would make more sense as a FDW itself as Table > AM currently knows nothing about Primary Keys and these are likely > needed for overlays) > > * Table AM as a (pl/)Python Class - this is inspired by the amazing > Multicorn [2] FDW-in-Python tool which made it ridiculously easy to > expose anything (mailbox, twitter feed, git commit history, > you-name-it) as a Foreign Table I cannot say how simple that is without seeing the code, but limiting the use of an AM to be linked to a single session sounds like a concept simple enough, limiting its relpersistence on the way. One thing that may be also interesting is something that does not go through the Postgres buffer pool. > Included Mark Dilger directly to this mail as he mentioned he has a > Perl script that makes a functional copy of heap AM that can be > compiled as installed as custom AM. Similar discussion has happened in 640c198 related to the creation of dummy_index_am, where the argument is that such a module needs to provide value in testing some of the core internals. dummy_index_am did so for reloptions on indexes because there was not much coverage for that part of the system. > @mark - maybe you can create 3 boilerplate Table AMs for the above > named `mem_am`, `overlay_am` and `py3_am` and we could put them > somewhere for interested parties to play with ? Not sure if that's worth counting, but I also have a table AM template stored in my plugin repo: https://github.com/michaelpq/pg_plugins/tree/main/blackhole_am It does as much as its name states, being able to eat all the data fed to it. -- Michael
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