Lookup operation
A lookup operation locates or retrieves data associated with a specified key, identifier, index, or other locating value.
Apache Kafka in Action
A lookup is the retrieval of a corresponding value from stored state by a key or identifier.
- How it is used
- Uses keyed table state to enrich or join each incoming stream message with its corresponding stored record.
- How deep it goes
- Explains per-message state lookup through stream-table joins and data enrichment, without descending into state-store internals.
- Examples
- Demonstrates product-sales enrichment and loyalty-card customer joins using keyed tables.
- What you can do after
- Apply it via stream-table join APIs to enrich incoming records with current master or reference data.
Learn Haskell by Example
lookup is a standard Haskell function that searches an associative list for a key and returns its associated value when present.
- How it is used
- Implements value retrieval for maps built from associative lists and supports graph-based programs.
- How deep it goes
- Explains recursive traversal, Maybe results, defaults, and worst-case full-list scanning, then points toward replacement.
- Examples
- Uses AssocMap definitions, findWithDefault, graph lookups, and a profiling report showing lookup as the main cost center.
- What you can do after
- Builds a recursive map lookup, handles missing keys with defaults, and diagnoses associative-list performance bottlenecks.
Read how Learn Haskell by Example explains lookup operation →
Related concepts
- constant timemeasured by · Constant time is an asymptotic complexity in which the running time remains bounded independently of input size, conventionally denoted O(1).
- embeddingimplemented by · A numerical vector representation of an item or input that encodes features or relationships useful for computational tasks.
- nonclustered indexuses · A nonclustered index is a separate database structure that stores keys and row locators without determining a table’s physical row order.
- moduleproduced by · A module is a distinct, bounded software unit that groups related code or functionality and provides an organizational or interaction boundary within a larger system.
- false positiveproduces · A false positive is a result that incorrectly indicates a condition or class is present when it is absent.
- Mapuses · A map is an associative data structure that stores key-value pairs and supports retrieving values by key.
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