FOSDEM 2025 — UUID Standards in Open Source Databases

FOSDEM 2025 was held in Brussels on February 1–2, 2025. The Free and Open Source Software Developers’ European Meeting draws over 8,000 attendees and features devrooms across dozens of technology domains. The databases devroom and the PostgreSQL developer room both featured UUID-related content.

PostgreSQL Devroom — UUID v7 Implementation Review

The PostgreSQL devroom hosted a technical session reviewing the internal implementation of uuidv7() scheduled for PostgreSQL 18. The session covered:

• The timestamp extraction algorithm: read clock_gettime(CLOCK_REALTIME) in the backend, convert to Unix milliseconds, pack into the high 48 bits
• The random bit generation: uses PostgreSQL’s internal CSPRNG (pg_strong_random), the same source used by gen_random_uuid()
• The monotonic counter: PostgreSQL 18’s implementation does not include a per-session monotonic counter by default — rapid successive calls within the same millisecond produce UUIDs with equal timestamps and independent random bits

The session noted that the lack of a monotonic counter is consistent with RFC 9562’s optional treatment of Method 1. For applications that require within-millisecond ordering, application-layer generation with a library that implements a counter (like the uuid npm package) is recommended.

MariaDB and MySQL Status

A cross-database session compared UUID v7 support across the major open source relational databases:

For MariaDB and MySQL deployments, the recommended pattern remains application-layer generation with BINARY(16) storage:

-- MariaDB / MySQL
CREATE TABLE orders (
    id BINARY(16) PRIMARY KEY,
    status VARCHAR(50) NOT NULL
);

INSERT INTO orders (id, status)
VALUES (UUID_TO_BIN(?, 1), 'pending');
-- The second argument `1` swaps byte groups for better index locality

Open Source ORM Sessions

Talks on SQLAlchemy and Django ORM covered the ORM-level changes needed to take advantage of PostgreSQL 18’s native uuidv7():

SQLAlchemy 2.x:

from sqlalchemy import Column, text
from sqlalchemy.dialects.postgresql import UUID

class Order(Base):
    __tablename__ = "orders"
    id = Column(UUID(as_uuid=True), primary_key=True,
                server_default=text("uuidv7()"))

server_default=text("uuidv7()") tells SQLAlchemy to let PostgreSQL generate the value, ensuring every insert — including raw SQL — gets a UUID v7.

Extension Ecosystem

Talks also covered the pg_uuidv7 extension as a bridge for PostgreSQL 14–17 users who cannot yet upgrade to PostgreSQL 18. The extension provides uuid_generate_v7() with identical semantics to the upcoming built-in.

Related Open Source Resources

• FOSDEM 2025 talk recordings
• PostgreSQL 18 UUID functions documentation
• MariaDB UUID v7 JIRA ticket
• pg_uuidv7 extension for PostgreSQL 14–17
• MySQL UUID_TO_BIN documentation
• RFC 9562 — UUID v7 specification