NOTE
Elasticsearch Analyzers
Character filters, tokenizers, token filters, index/search analyzers, and why analysis is part of the search schema.
This is a historical learning note and may contain outdated or incomplete understanding.
An analyzer converts text into searchable tokens through a pipeline commonly composed of character filters, a tokenizer, and token filters.
Index-time and search-time analysis must be compatible with the intended matching semantics. Language-specific tokenization, lowercasing, stemming, synonyms, n-grams, and normalization can dramatically change recall/precision and index size.
Treat analyzer configuration as part of the index schema. Changing analysis for existing data generally requires reindexing into a new mapping/index generation.