pg_map

pg_lake : Map type for PostgreSQL, bundled as a required pg_lake component.

Overview

Packages

Source

pig build pkg pg_lake;		# build rpm/deb

Install

Make sure PGDG and PIGSTY repo available:

pig repo add pgsql -u   # add both repo and update cache

Install this extension with pig:

pig install pg_lake;		# install via package name, for the active PG version
pig install pg_map;		# install by extension name, for the current active PG version

pig install pg_map -v 18;   # install for PG 18
pig install pg_map -v 17;   # install for PG 17
pig install pg_map -v 16;   # install for PG 16

Create this extension with:

CREATE EXTENSION pg_map;

Usage

Sources:

• pg_map README at the reviewed commit
• pg_map install SQL at the reviewed commit
• pg_map C implementation at the reviewed commit

pg_map applies a one-argument PostgreSQL function to every element of an array and returns an array of the function results. Its two overloads identify the mapped function by OID or by text; a text signature containing parentheses is resolved as a specific regprocedure, while a bare name is resolved as regproc.

Map a Function over an Array

CREATE EXTENSION pg_map;

SELECT pg_map(
  'upper(text)',
  ARRAY['alpha', 'beta', 'gamma']::text[]
);

The example applies upper(text) to each element and returns an uppercase text array. Supplying a full signature avoids ambiguity when a function name is overloaded.

Caveats

• Upstream only claims compatibility with PostgreSQL 9.6devel. It does not document support for modern PostgreSQL releases.
• The version 1.0 C implementation uses PostgreSQL internal array, catalog, and function-manager APIs. Build and regression-test it against the exact server source before use.
• The mapped function must accept one argument. The implementation attempts an element-type cast when the array element type differs from the function argument type and errors if no cast function is available.
• Upstream publishes no license or release compatibility matrix.