Keyword retrieval in Azure AI Search that uses an inverted index with BM25 ranking. It excels at exact matches on names, identifiers and product codes but does not catch paraphrased wording.
Also called keyword search.
Read more: Microsoft Learn
In the Ultra Transcenders books
Each book explains Full-text search in context, with comparison tables and the common traps.
Terms in this definition
- Azure AI Search
Managed Azure service that builds indexes over your content and answers keyword, vector, hybrid and semantically ranked queries, optionally with AI enrichment. Retrieval-augmented generation, Foundry agents and knowledge mining all use it to fetch relevant content.
- Index
Speeds up queries that filter on certain columns by keeping those columns sorted, with pointers back to each row; the price is more storage and slower writes.
- BM25
Full-text ranking function that weighs how often a term occurs, how rare it is across the corpus and how long each document is.
Related terms
- Hybrid search
One Azure AI Search request that performs vector and full-text search side by side and combines the results through Reciprocal Rank Fusion. Adding the semantic ranker yields the best relevance overall.
- LCID
A locale ID: a number standing for a language (British English, for instance, is 2057). In full-text search it decides which stemmer and word breaker are applied to an indexed column or a query.
- LIKE
Compares strings with a pattern that can contain the % and _ wildcards. Because it only understands character patterns, searching big volumes of text this way is much slower than using full-text search.