UUID_GENERATE_V4

Generate a new random UUID (version 4).

Syntax

UUID_GENERATE_V4()

Description

## Overview Generates a new random UUID conforming to version 4 of RFC 4122. This function exists as a compatibility alias for PG-compat code that expects the `uuid_generate_v4()` name from the `uuid-ossp` extension. UUID_GENERATE_V4 is semantically identical to UUID and GEN_RANDOM_UUID. ## Behavior - Non-deterministic: every call returns a different value. - Uses a cryptographically secure random source. - Returns a 36-character lowercase hyphenated string (version 4, variant 10xx). - Never returns NULL. - Side effect free. ## Compatibility - PG-compat alias for UUID and GEN_RANDOM_UUID.

Examples

-- Generate a single UUID
SELECT UUID_GENERATE_V4();

-- Use as a primary key value on insert
INSERT INTO crm.catalog.contacts (id, name)
VALUES (UUID_GENERATE_V4(), 'Acme Corp');

-- Each call produces a distinct value
SELECT UUID_GENERATE_V4() AS id_1, UUID_GENERATE_V4() AS id_2;

-- Freeze a UUID for reuse across references in the same query
WITH id AS (SELECT UUID_GENERATE_V4() AS v) SELECT id.v FROM id JOIN id i2 ON id.v = i2.v;

-- Round-trip validation
SELECT IS_UUID(UUID_GENERATE_V4()) AS ok;  -- true

Pitfalls

• Non-deterministic: the value changes on every call. Freeze in a CTE if you need the same UUID used in multiple expressions within one query.
• UUID v4 is explicitly random and is not time-ordered. For write-heavy time-series workloads, this can hurt index locality; consider a timestamp-prefixed scheme when ordering matters.
• This function name comes from a PG-compat extension. In pure ANSI SQL, prefer UUID() for portability.
• Do not parse the output to extract timestamps. Version 4 UUIDs contain no timing information.

See Also

• gen_random_uuid
• uuid
• is_uuid