MAP: Dynamic Key-Value Pairs

Concepts covered: dmMapType

Flexible Attributes Without Schema Changes A MAP column stores key-value pairs where the keys are not predefined in the schema. A user preferences column might contain {'theme': 'dark', 'language': 'en', 'notifications': 'off'}. Each user can have different keys. Adding a new preference does not require ALTER TABLE. MAPs are the escape hatch for data that does not have a fixed schema. Event properties, configuration settings, A/B test parameters, custom metadata. Anything where the set of keys varies per row and evolves over time. The Tradeoff The hybrid pattern: store the full event payload as a MAP or JSON column for flexibility, and extract frequently-queried fields as top-level typed columns for performance. The JSON column preserves everything; the typed columns make the hot-path quer

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