Composite

Row-shaped composite type declared with TYPE name AS (...).

Basic composite type

SCHEMA public {
    TYPE address AS (
        street      TEXT,
        city        TEXT,
        state       CHAR(2),
        postal_code TEXT,
        country     CHAR(2)
    );
}

-- emits
CREATE TYPE "public"."address" AS (
    "street"      text,
    "city"        text,
    "state"       char(2),
    "postal_code" text,
    "country"     char(2)
);

Adding an attribute

Adding an attribute emits ALTER TYPE ... ADD ATTRIBUTE — SAFE.

-- before
TYPE contact AS (name TEXT, email TEXT);

-- after (add phone)
TYPE contact AS (name TEXT, email TEXT, phone TEXT);

-- emits (SAFE)
ALTER TYPE "public"."contact" ADD ATTRIBUTE "phone" text;

Attribute comments and renames

Each attribute can carry its own { } block, written with PostgreSQL’s own ATTRIBUTE keyword. It accepts COMMENT and RENAMED FROM.

TYPE address AS (
    street_line TEXT,
    city        TEXT
) {
    ATTRIBUTE street_line {
        RENAMED FROM street;
        COMMENT 'First line of the street address';
    }
}

-- emits
ALTER TYPE "public"."address" RENAME ATTRIBUTE "street" TO "street_line";
COMMENT ON COLUMN "public"."address"."street_line" IS 'First line of the street address';

Several attributes can be grouped in a plural block:

TYPE address AS (street TEXT, city TEXT) {
    ATTRIBUTES {
        street { COMMENT 'Street and number'; }
        city   { COMMENT 'City name'; }
    }
}

Changes and safety

Change	DDL emitted	Safety
Attribute added	`ALTER TYPE name ADD ATTRIBUTE attr type`	`SAFE`
Attribute removed	`ALTER TYPE name DROP ATTRIBUTE attr`	`DESTRUCTIVE`
Attribute type or `COLLATE` changed	`ALTER TYPE name ALTER ATTRIBUTE attr TYPE type`	`DESTRUCTIVE`
Attribute renamed (`RENAMED FROM`)	`ALTER TYPE name RENAME ATTRIBUTE old TO new`	`SAFE`
Attribute comment changed	`COMMENT ON COLUMN name.attr IS '...'`	`SAFE`