cztamas-plv8ify-experiment

PLV8ify

Introduction

plv8ify bundles typescript/javascript input and writes SQL file(s) containing Postgres functions using PLV8.

Why

• Interchange code between API and Database
• Write code in Typescript and use it in Postgres

Example

1. npm install -g plv8ify
2. Sample input.ts

const { point: turfPoint } = require('@turf/helpers')

export function point(lat, long) {
  const pt = turfPoint([lat, long])
  return pt
}

1. Run plv8ify generate
2. Step 3 emits SQL file with names like ./plv8-dist/plv8ify_point.plv8.sql (one for each exported function)
3. Execute the generated ./plv8-dist/plv8ify_point.plv8.sql using a Postgres client
4. Call the generated function using a Postgres client SELECT plv8ify_point(52.5200,13.4050);

See all examples in the examples folder. Use yarn examples to apply any changes to all the examples.

Deploy on custom schema

To generate a function to be deployed on a schema different than the default one (usually: public) decorate the function with a //@plv8ify-schema-name <schemaname> comment

//@plv8ify-schema-name testschema
export function hello() {
  return 'world'
}

will generate

DROP FUNCTION IF EXISTS testschema.plv8ify_hello();
CREATE OR REPLACE FUNCTION testschema.plv8ify_hello() RETURNS text AS $plv8ify$
// input.ts
function hello() {
  return "world";
}


return hello()

$plv8ify$ LANGUAGE plv8 IMMUTABLE STRICT;

Trigger functions

To write a trigger function, the name of the function should end with Trigger, and have the function return a testRow type where testRow defines the type of the row for the trigger. You can also add a NEW parameter for insert and update triggers, and OLD for update and delete triggers. (Tip: you can add @types/pg and @types/plv8-internals to get all standard postgres types/defines and plv8 specific functions recognized by the type checker)

type Row = {
  // Either JS or plv8 types can be used here
  id: number
  event_name: string
  event_date_time: Date
}

export function testTrigger(NEW: Row, OLD: Row): Row {
  plv8.elog(NOTICE, 'NEW = ', JSON.stringify(NEW));
  plv8.elog(NOTICE, 'OLD = ', JSON.stringify(OLD));
  plv8.elog(NOTICE, 'TG_OP = ', TG_OP);
  plv8.elog(NOTICE, 'TG_ARGV = ', TG_ARGV);
  if (TG_OP === 'UPDATE') {
    NEW.event_name = NEW.event_name ?? OLD.event_name
    return NEW
  }
  if (TG_OP === 'INSERT') {
    NEW.id = 102
    return NEW
  }
}

Custom Postgres Types

By default plv8ify converts typescript types to postgres types using the following map:

  private _typeMap = {
    number: 'float8',
    string: 'text',
    boolean: 'boolean',
  }

and defaults all other types to either JSONB or the type passed in using the --fallback-type option It is possible to define additional type mapping by using a custom file (by default types.ts) with the following format:

typeMap = {
  test_type: 'test_type',
  'test_type[]': 'test_type[]',
}

The custom types will be merged with the default ones at runtime and will allow using either internal postgres type or custom defined types

Example: types.ts

typeMap = {
  test_type: 'test_type',
  'test_type[]': 'test_type[]',
}

input.ts

interface test_type {
  name: string
  age: number
}

export function hello(test: test_type[]) {
  return {
    name: `Hello ${test[0].name}`,
    age: test[0].age,
  }
}

cli command line:

plv8ify generate input.ts --types-config-file types.ts

will generate this function:

DROP FUNCTION IF EXISTS plv8ify_hello(test test_type[]);
CREATE OR REPLACE FUNCTION plv8ify_hello(test test_type[]) RETURNS JSONB AS $plv8ify$
// input.ts
function hello(test) {
  return {
    name: `Hello ${test[0].name}`,
    age: test[0].age
  };
}


return hello(test)

$plv8ify$ LANGUAGE plv8 IMMUTABLE STRICT;

CLI Usage

Version

Print the version

Generate Command Flags	Type	Description	Default

Generate

Generate PLV8 functions for an input typescript file

Generate Command Flags	Type	Description	Default
--debug	Boolean	Print additional debug information	false
--bundler	'esbuild' or 'bun'	Pick bundler. Bun runtime is needed for 'bun'	esbuild
--write-bundler-output	Boolean	Write the intermediate bundled Javascript output from bundler (currently, only ESBuild interface exists)	false
--input-file	String	Specify an input file path (only Typescript supported at the moment)	input.ts
--output-folder	String	Specify an output folder	plv8ify-dist
--scope-prefix	String	Specify a scope prefix, by default (empty string), adds provided string as prefix for exported typescript functions	plv8ify
--pg-function-delimiter	String	Specify a delimiter for the generated Postgres function	$plv8ify$
--fallback-type	String	Specify a fallback type when plv8ify fails to map a detected Typescript type to a Postges type	JSONB
--mode	'inline', 'bundle' or 'start_proc'	'inline' will bundle the library in each function, both 'bundle' and 'start_proc' creates a {prefix}_init function that loads the library. 'bundle' adds a check to each function to call 'init' if required, whereas 'start_proc' is designed to be used with plv8.start_proc	inline
--volatility	'IMMUTABLE' or 'STABLE' or 'VOLATILE'	Change the volatility of all the generated functions. To change volatility of a specific function use the comment format //@plv8ify-volatility-STABLE in the input typescript file (see examples/turf-js/input.ts). Note that for now only single-line comment syntax is supported.	IMMUTABLE
--types-config-file	String	Specify a custom types config file	types.ts

Deploy

Deploy an output folder to a Postgres database (defined by env var DATABASE_URL)

Generate Command Flags	Type	Description	Default
--output-folder	String	Specify an output folder	plv8ify-dist

Caveats

• Very early, only a small number of types supported
• Only supports typescript as input at the moment
• Scaling an application server is easier than scaling a database server, moving the logic in database as postgres functions makes it easier (IMO SQL is declarative, like React for data) to call the code/do some things but you are effectively shifting compute from application server to database server which might be a bad idea in most cases.

Prior Art

• https://github.com/CSTARS/es6-to-plv8
• https://github.com/clkao/plv8x

Contact

If you want to reach out to me, please DM me on https://twitter.com/divyenduz or email me at mail at divyendusingh.com