Plugins built with newer PDKs don't work with pg_extism

[jrandall]

I have managed to successfully use pg_extism to build a replacement for a C-language postgres user-defined function by compiling it to webassembly and running it on Amazon RDS using pg_extism with PLV8. This is great, thanks!

However, in order to do this, I had to use a pre-1.0 version of the extism c-pdk, as it seems a number of host interfaces are missing in pg_extism. In case others may find this useful, I found the current version of pg_extism works well with c-pdk commit ref 01064c00d7de7532132e7bf7305c4eaf486b6658.

Some of the things that are used by c-pdk plugins in v1.1 that seem to be missing from pg_extism are host functions in extism:host/env:

• the input_offset function
• the log_trace function
• the get_log_level function

The latter two seem fairly trivial to add (both can just be adopted from current versions in js-sdk: https://github.com/extism/js-sdk/blob/b46fb76549ee006e099129a395926406dde1d122/src/call-context.ts#L415-L419), but the input_offset function in js-sdk seems like it is based around an input data structure that has been changed significantly in js-sdk compared to the version in pg_extism. The current implementation in js-sdk (https://github.com/extism/js-sdk/blob/b46fb76549ee006e099129a395926406dde1d122/src/call-context.ts#L263-L266) is referring to a Block class that pg_extism does not seem to be using.

The extism c-pdk v1.1 high level input loading function extism_load_input has been updated to use the input_offset function, so it is fairly essential to plugin function for this to work with versions of the c-pdk after the v1.0 release.

[mhmd-azeez]

Hello @jrandall, thanks for reporting the issue, I have opened a PR (#8) that should fix the problem, can you please take a look at and test it out?

[jrandall]

Thanks @mhmd-azeez so much for the rapid work to implement this. I can confirm that PR #8 fixes these issues for me and works with c-pdk 1.1.0.

[mhmd-azeez]

@jrandall perfect, thanks for trying it out!

[jrandall]

@mhmd-azeez while the update does now compile and run with c-pdk 1.1.0, I've found that neither logging nor higher level input functions appear to work properly. My testing earlier was still using the lower-level input loading rather than the extism_load_input function - when I use this, I get empty input.