https://github.com/dylibso/pg_extism

Wasm UDFs for Postgres, implemented as a TLE on plv8 using Extism
https://github.com/dylibso/pg_extism

extism postgresql udf wasm

Last synced: about 2 months ago
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Wasm UDFs for Postgres, implemented as a TLE on plv8 using Extism

• Host: GitHub
• URL: https://github.com/dylibso/pg_extism
• Owner: dylibso
• License: bsd-3-clause
• Created: 2023-08-18T07:11:18.000Z (over 1 year ago)
• Default Branch: main
• Last Pushed: 2024-08-27T17:56:29.000Z (5 months ago)
• Last Synced: 2024-12-08T06:31:06.324Z (about 2 months ago)
• Topics: extism, postgresql, udf, wasm
• Language: TypeScript
• Homepage:
• Size: 3.79 MB
• Stars: 30
• Watchers: 8
• Forks: 1
• Open Issues: 1
• Metadata Files:
  • Readme: README.md
  • License: LICENSE

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README

        
# pg_extism

**Note**: This is an experimental SDK.

## Getting started

Make sure [`plv8`](https://github.com/plv8/plv8) is installed on your server. Then enable it for your database:

```sql

create extension plv8;

```

Now run the script in [dist/index.sql](./dist/index.sql) and you'll get two SQL functions: `extism_create_plugin` and `extism_call`.

## Use pg_extism

Assume you have a table called `plugins`:

```sql

CREATE TABLE public.plugins (

	id int4 GENERATED ALWAYS AS IDENTITY( INCREMENT BY 1 MINVALUE 1 MAXVALUE 2147483647 START 1 CACHE 1 NO CYCLE) NOT NULL,

	"data" bytea NULL,

	"name" varchar NULL,

	CONSTRAINT plugins_pk PRIMARY KEY (id)

);

```

Insert a few plugins into the table. And then call:

```sql

select extism_call(data, 'count_vowels', 'Hello World!') from plugins where id = 2;

```

**Note:** this assumes the plugin with id `2` has a function called `count_vowels`. You can find the plugin [here](https://github.com/extism/plugins/releases).

If you want more control over your plugin, you can use `extism_create_plugin`:

```sql

-- DROP FUNCTION public.count_vowels_kv(varchar);

CREATE OR REPLACE FUNCTION public.count_vowels_kv(input character varying)

 RETURNS character varying

 LANGUAGE plv8

AS $function$

	const createPlugin = plv8.find_function("extism_create_plugin");

	const wasm = plv8.execute("select data from plugins where id = 3")[0];

	const opts = {

		useWasi: true,

		

		functions: {

			"extism:host/user": {

				kv_read(cp, offs) {

	                const key = cp.read(offs).text();

				    let result = plv8.execute("SELECT value FROM kv WHERE key = $1", [key]);

				    let value = result.length > 0 ? result[0].value : new Uint8Array([0, 0, 0, 0]);

				    return cp.store(value);

	            },

	            kv_write(cp, kOffs, vOffs) {

					const key = cp.read(kOffs).text();

				    const value = cp.read(vOffs).bytes();

				    let result = plv8.execute("SELECT value FROM kv WHERE key = $1", [key]);

				    if (result.length > 0) {

				        plv8.execute("UPDATE kv SET value = $1 WHERE key = $2", [value, key]);

				    } else {

				        plv8.execute("INSERT INTO kv (key, value) VALUES ($1, $2)", [key, value]);

				    }

	            }

			}

		}

	};

	const plugin = createPlugin(wasm, opts);

	return plugin.call("count_vowels", input).text()

$function$

;

```

The above example shows how you can use `extism_create_plugin` to supply your own host functions to the plugin. You can find th source code for the plugin [here](https://github.com/extism/plugins/tree/main/count_vowels_kvstore).