Täistekstindeksi

Täistekstindeksi refers to a full-text index, a data structure used by database search engines and other information retrieval systems to allow for fast searching of textual content. Instead of relying on predefined fields or keywords, a full-text index analyzes and stores every word (or token) within a document or a collection of documents. This enables users to search for specific words or phrases, and the index helps locate the documents containing them very efficiently.

The process of creating a full-text index typically involves several steps. First, the text is tokenized, meaning it's broken down into individual words or meaningful units. Stop words, such as common articles and prepositions (like "the," "a," "is"), are often removed as they are unlikely to be important for search relevance. Stemming or lemmatization may also be applied to reduce words to their root form, so that variations of a word (e.g., "run," "running," "ran") are treated as the same term. These processed tokens are then stored in an inverted index, which maps each unique word to a list of documents where it appears, and often includes positional information within those documents.

Full-text indexing is crucial for applications like web search engines, document management systems, and e-discovery tools, where the ability to search through large volumes of unstructured text is paramount. It allows for sophisticated search queries, including phrase searching, proximity searching, and relevance ranking based on word frequency and distribution.