Universally unique identifier
A universally unique identifier (UUID) is a standardized 128-bit identifier designed to distinguish entities with an extremely low probability of collision across independently generated values.
The Well-Grounded Python Developer: How the pros use Python and Flask
A universally unique identifier (UUID) is a standardized 128-bit identifier conventionally represented as a hexadecimal string and intended to be globally unique.
- How it is used
- Identifies user records during authentication and keeps primary keys distinct when database tables are merged.
- How deep it goes
- Explains UUID primary keys through a generator and table-merge scenario, but does not detail identifier internals.
- Examples
- Illustrates a generated User key, conflicting integer IDs during a table merge, and integer-versus-UUID order URLs.
- What you can do after
- Apply it via Python’s `uuid4()` and SQLAlchemy to assign UUID primary keys to user records.
Data Pipelines with Apache Airflow, Second Edition
A UUID is a universally unique identifier represented as a fixed-format value intended to identify an entity with extremely low collision probability.
- How it is used
- Identifies recipe and chunk content so an ingestion pipeline can choose creation, update, or no processing.
- How deep it goes
- Works through UUID generation, whitespace normalization, schema properties, and comparison decisions; does not detail the generation algorithm.
- Examples
- Uses ingredient and instruction chunks, `generate_uuid5` calls, UUID-typed collection fields, and create/update/unchanged recipe cases.
- What you can do after
- Build it from scratch using `generate_uuid5` for recipe and chunk keys, then compare them to classify incoming records.
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100 SQL Server Mistakes and How to Avoid Them
A globally unique identifier (GUID) is a 16-byte identifier designed to be unique across a broad system scope.
- How it is used
- Uses GUIDs to assess primary-key design trade-offs and to identify symmetric keys during encryption.
- How deep it goes
- Explains GUID size and clustered-index write consequences, but defers deeper GUID generation internals.
- Examples
- Demonstrates NEWID() for GUID generation and KEY_GUID('SalaryKey') within ENCRYPTBYKEY() for salary encryption.
- What you can do after
- Evaluate/understand when GUID primary keys impose index-storage, fragmentation, and write-performance costs.
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ScyllaDB in Action
A UUID is a standardized 128-bit identifier format designed to provide uniqueness across systems and commonly represented as hexadecimal characters.
- How it is used
- Uses UUID-based types to assign unique entity and primary-key identifiers in ScyllaDB data models.
- How deep it goes
- Explains formatting, binary storage, randomness, temporal ordering, generation functions, and selection trade-offs; defers detailed UUID versions.
- Examples
- Demonstrates uuid() and now() in CQL and assigns TIMEUUID values to article, summary, and author identifiers.
- What you can do after
- Operate/configure ScyllaDB identifiers by choosing UUID or TIMEUUID and generating values with CQL or application code.
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Data-Oriented Programming: Reduce software complexity
A UUID is a 128-bit identifier represented in a standardized textual form and designed for practical global uniqueness.
- How it is used
- Uses UUIDs to create distinct filenames for captured data used by unit tests.
- How deep it goes
- Defines UUID-based naming and library choices, but stops short of explaining UUID generation internals or collision probabilities.
- Examples
- Demonstrates UUIDs in captured search data paths and replayable JSON fixtures.
- What you can do after
- Apply it via a UUID library to generate distinct filenames for captured test data.
Kubernetes for Developers
A UUID is a 128-bit identifier designed to be generated with a very low probability of collision across clients and systems.
- How it is used
- Supports horizontally scalable databases by letting clients generate record identifiers independently.
- How deep it goes
- Defines the identifier and explains its scaling rationale, but stops short of generation algorithms or implementation details.
- Examples
- Uses the identifier 8fe05a6e-e65d-11ea-b0da-00155d51dc33 as a concrete hexadecimal example.
- What you can do after
- Apply UUIDs when independently generated identifiers support scaling better than centralized incrementing keys.
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Just Use Postgres!
A UUID is a standardized 128-bit identifier designed to be globally unique without relying on a database sequence.
- How it is used
- Uses UUIDs as database primary keys when applications need identifiers independent of numeric sequences.
- How deep it goes
- Defines UUID primary keys and generation functions, but defers broader identifier design and administration.
- Examples
- Demonstrates UUIDs in sales.orders and order_items, including a generated default and an application-supplied order identifier.
- What you can do after
- Operate/configure Postgres tables with UUID primary keys and generate values through defaults or application input.
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Amazon Web Services in Action, Third Edition: An in-depth guide to AWS
A UUID is a standardized 128-bit identifier designed to be unique across systems and generated without centralized coordination.
- How it is used
- Uses client-generated identifiers to address distributed objects and make database operations idempotent across retries.
- How deep it goes
- Defines UUIDs and demonstrates insert-if-absent behavior, but does not explain generation algorithms or collision probabilities.
- Examples
- Uses an object-store key and a blog-post UUID, including the value 550e8400-e29b-11d4-a716-446655440000.
- What you can do after
- Apply UUIDs as client-generated primary keys to prevent duplicate database records during retries.
PostgreSQL Mistakes and How to Avoid Them
UUID is a 128-bit identifier data type whose values are conventionally represented as 32 hexadecimal digits separated by hyphens.
- How it is used
- Frames UUIDs as identifier choices in PostgreSQL schema and performance decisions.
- How deep it goes
- Defines UUIDs, explains UUIDv4, and measures storage and indexing costs, but does not survey UUID variants beyond UUIDv4.
- Examples
- Demonstrates UUIDv4 and bigint identifiers through 100-million-row inserts, timing output, column sizes, and primary-key index sizes.
- What you can do after
- Evaluate UUID versus bigint identifier costs using PostgreSQL timing, column-size, and index-size measurements.
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Practical Automation with PowerShell: Effective scripting from the console to the cloud
A universally unique identifier (UUID), also commonly called a GUID, is a 128-bit identifier designed to distinguish entities with an extremely low probability of collision.
- How it is used
- Prevents output collisions when multiple remote systems write results to shared storage.
- How deep it goes
- Defines GUID structure and generation, but stops short of explaining UUID versions or generation internals.
- Examples
- Uses remote extension collection, shared output files, system names, and New-Guid-generated filename components.
- What you can do after
- Apply it via New-Guid to create safer unique names for distributed PowerShell output.
Related concepts
- Objectpart of · java.lang.Object is the root class of Java’s reference-type hierarchy and defines methods inherited by Java reference types.
- unique identifierkind of · A unique identifier is a value or name that distinguishes an entity or record from others within a defined scope or namespace.
- structkind of · A struct is a composite data type or structure that groups related fields or values into a single unit.
- Weaviateused by · Weaviate is an open-source vector database and search engine for storing, indexing, and retrieving data using vector representations.
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