Denormalization Done Right: Optimizing Data Access in Datastores
Shifting from Database to Datastore Thinking: A Beginner's Guide
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Databases (e.g., MySQL, PostgreSQL):
- Structured data: Information is organized in tables with rows (records) and columns (attributes).
- Schema-based: Defines the structure and data types of each table upfront.
- Relational: Tables are linked through foreign keys, enabling complex queries across them (e.g., JOINs).
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Datastores (e.g., Google App Engine Datastore):
- Semi-structured data: Allows flexible data formats, accommodating diverse information within a single entity.
- Schema-less (partially enforced): Defines basic constraints later, adapting to evolving data needs.
- Non-relational: No table relationships, requiring queries within entities or separate denormalized structures.
Thinking in Datastores:
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Entities and Properties:
- Imagine data as entities (like objects), each holding its own properties (like attributes).
- Example:
# Entity representing a user user = { "name": "foo", "email": "[email protected]", "age": 30, "interests": ["books", "music"] }
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Keys and Queries:
- Each entity has a unique key for identification and retrieval.
- Queries filter and retrieve entities based on their properties, but without JOINs between entities.
- Example: Find users older than 25:
# Query for users with age greater than 25 users = datastore.query(kind="User").filter("age >", 25)
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Denormalization:
- Since JOINs are absent, consider denormalization to avoid repeated queries.
- Duplicate some data in relevant entities for faster retrieval.
- Example: Store a user's name in both the user entity and their post entities for efficient access.
Related Issues and Solutions:
- Data Complexity: Datastores may struggle with complex relationships compared to relational databases. Consider alternative solutions like separate services or redesigning data structures for denormalization.
- Advanced Queries: Datastores might lack the full power of complex SQL queries. Explore alternative querying mechanisms or consider a hybrid approach using both datastores and relational databases for specific needs.
database google-app-engine google-cloud-platform