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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> */ jsdoc tag

/** @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, decorate the function with a /** @plv8ify_trigger */ jsdoc tag, 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
}

/** @plv8ify_trigger */
export function test(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;

Additionally, you can decorate your functions with special jsdoc tags to control the type mapping of params and return types on a per function basis:

Example:

input.ts

/**
 * @plv8ify_param {varchar(255)} first_name
 * @plv8ify_param {text} last_name
 * @plv8ify_return {char(255)}
 */
export function howdy(first_name: string, last_name: string): string {
  return `Howdy ${first_name} ${last_name}`
}

cli command line:

plv8ify generate input.ts

will generate this function:

DROP FUNCTION IF EXISTS howdy(first_name varchar(255),last_name text);
CREATE OR REPLACE FUNCTION howdy(first_name varchar(255),last_name text) RETURNS char(255) AS $plv8ify$
// examples/hello-custom-type/input.ts
function hello(test) {
  return {
    name: `Hello ${test[0].name}`,
    age: test[0].age
  };
}
function howdy(first_name, last_name) {
  return `Howdy ${first_name} ${last_name}`;
}


return howdy(first_name,last_name)

$plv8ify$ LANGUAGE plv8 IMMUTABLE STRICT;

JSDoc Tag Reference

Behavior JSDoc Tag Example
set the volatility of the generated Postgres function /** @plv8ify_volatility <STABLE,IMMUTABLE,VOLATILE> */ /** @plv8ify_volatility STABLE */
set the schema of the generated Postgres function /** @plv8ify_schema_name <schemaname> */ /** @plv8ify_schema_name my_schema */
set the TS->SQL type mapping for a parameter /** @plv8ify_param {<my_sql_type>} <my_param> */ /** @plv8ify_param {timestamptz} ts */
set the TS->SQL type mapping for the return type /** @plv8ify_returns {<SQL TYPE>} */ /** @plv8ify_returns {setof my_table} */
designate the function is a TRIGGER /** @plv8ify_trigger */ /** @plv8ify_trigger */

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 jsdoc /** @plv8ify_volatility STABLE in the input typescript file (see examples/turf-js/input.ts). 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
--deploy-concurrency Number Specify the maximum allowed deployment tasks to run in parallel 10

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

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