The key differences v4 vs v7
Understanding structure, performance, and database implications
Structure & generation
Version 4
Random
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- 122 bits of pure randomness
- Maximum entropy
- No temporal sorting
Draft Spec
Version 7
Time-Ordered
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- 48-bit timestamp (milliseconds)
- 74 bits of randomness
- Natural time-based sorting
Version 7 draft status
Specification
Draft-04- IETF Draft "New UUID Formats"
- Stable specification
- Wide industry adoption
Implementation
Production Ready- PostgreSQL 13+ support
- Multiple language libraries
- Major cloud platform adoption
Performance impact
Database performance
Index operations
1x
v4 baseline
Random distribution
2.1x
v7 faster
Sequential writes
Range queries
1x
v4 baseline
Full scan needed
95x
v7 faster
B-tree optimized
Storage impact
Index size
2.1GB
v4 index
Fragmented
1.4GB
v7 index
Optimized
System impact
Page splits
48%
v4 rate
Random inserts
12%
v7 rate
Sequential inserts
Memory usage
1.2GB
v4 cache
Index cache
0.8GB
v7 cache
Index cache
Generation speed
Operations/second
10M
v4 speed
Pure random
8M
v7 speed
With timestamp
Real-world applications
High-scale systems
- Event sourcing systems: 100M+ events/day
- Distributed logging platforms
- Multi-region data synchronization
Time-critical apps
- Financial transaction systems
- Audit logging platforms
- Real-time analytics engines
Security & integration
Security considerations
UUID v4
- Unpredictable sequence
- No timestamp exposure
UUID v7
- Timestamp visible in ID
- Partial randomness maintained
Integration patterns
Distributed systems
- Multi-node generation
- Cross-region synchronization
Event systems
- Natural event ordering
- Causal consistency
Migration strategy
PostgreSQL migration
Open Source1. Enable UUID support
CREATE EXTENSION IF NOT EXISTS "uuid-ossp";
2. Add new column
ALTER TABLE users ADD COLUMN new_id uuid;
UPDATE users SET new_id = uuid_generate_v7();
CREATE INDEX CONCURRENTLY idx_users_new_id ON users(new_id);
UPDATE users SET new_id = uuid_generate_v7();
CREATE INDEX CONCURRENTLY idx_users_new_id ON users(new_id);
3. Validate & switch
BEGIN;
ALTER TABLE users DROP CONSTRAINT users_pkey;
ALTER TABLE users ADD PRIMARY KEY (new_id);
ALTER TABLE users DROP COLUMN id;
ALTER TABLE users RENAME COLUMN new_id TO id;
COMMIT;
ALTER TABLE users DROP CONSTRAINT users_pkey;
ALTER TABLE users ADD PRIMARY KEY (new_id);
ALTER TABLE users DROP COLUMN id;
ALTER TABLE users RENAME COLUMN new_id TO id;
COMMIT;
Performance impact
2.1x
Write speed
4.8x
Read speed
-35%
Index size
SQL Server migration
Enterprise1. Create helper function
CREATE FUNCTION dbo.GenerateUUIDv7()
RETURNS UNIQUEIDENTIFIER
AS BEGIN
RETURN CAST(
CAST(SYSDATETIME() AS BINARY(6)) +
CAST(NEWID() AS BINARY(10))
AS UNIQUEIDENTIFIER)
END
RETURNS UNIQUEIDENTIFIER
AS BEGIN
RETURN CAST(
CAST(SYSDATETIME() AS BINARY(6)) +
CAST(NEWID() AS BINARY(10))
AS UNIQUEIDENTIFIER)
END
2. Add new column
ALTER TABLE Users ADD NewId UNIQUEIDENTIFIER
DEFAULT dbo.GenerateUUIDv7();
CREATE INDEX IX_Users_NewId ON Users(NewId);
DEFAULT dbo.GenerateUUIDv7();
CREATE INDEX IX_Users_NewId ON Users(NewId);
3. Switch primary key
BEGIN TRANSACTION;
ALTER TABLE Users DROP CONSTRAINT PK_Users;
ALTER TABLE Users ADD CONSTRAINT
PK_Users PRIMARY KEY CLUSTERED (NewId);
ALTER TABLE Users DROP COLUMN Id;
EXEC sp_rename 'Users.NewId', 'Id', 'COLUMN';
COMMIT;
ALTER TABLE Users DROP CONSTRAINT PK_Users;
ALTER TABLE Users ADD CONSTRAINT
PK_Users PRIMARY KEY CLUSTERED (NewId);
ALTER TABLE Users DROP COLUMN Id;
EXEC sp_rename 'Users.NewId', 'Id', 'COLUMN';
COMMIT;
Performance impact
1.8x
Write speed
3.2x
Read speed
-28%
Page splits
Making the right choice
Choose UUID v7 when
- Building new applications
- Time-based data retrieval is important
- Database performance is critical
- Large-scale data operations
Keep UUID v4 when
- Maximum randomness is required
- Maintaining existing systems
- Small-scale applications
- Simple data access patterns