= Full Text Search in VitaDiet =

== Introduciton == 

Full Text Search (FTS) is a technique for searching natural language text in a database. Unlike a simple LIKE search which matches exact character patterns, FTS understands language — it normalizes words to their root form, ignores common words like "the" and "a", and ranks results by relevance.

For example a LIKE search for '%chicken%' will:
*Scan every row in the table sequentially
*Only match the exact string "chicken"
*Return results in no particular order
*Become slower as the table grows

A FTS search for 'chicken' will:
*Use a GIN index to find matches instantly
*Match "chicken", "chickens", "chickened"
*Rank results by relevance
*Perform consistently regardless of table size

For VitaDiet, FTS is used to power the food search feature, allowing users to search 350,000+ foods quickly and accurately.

== How PostgreSQL FTS Works ==

PostgreSQL FTS is built around two core data types:

tsvector — a preprocessed representation of a text document. It stores the normalized lexemes (root forms of words) of a text column. For example:
SELECT to_tsvector('english', 'Grilled Chicken Breast');
Result: 'breast':3 'chicken':2 'grill':1
*"Grilled" becomes "grill" (stemmed to root form)
*Numbers indicate the position of each word
*Stop words like "and", "the" are removed

tsquery — a processed search query. It converts user input into a format that can be matched against a tsvector:
SELECT plainto_tsquery('english', 'grilled chicken');
Result: 'grill' & 'chicken'
The @@ operator checks if a tsquery matches a tsvector:
SELECT to_tsvector('english', 'Grilled Chicken Breast') 
    @@ plainto_tsquery('english', 'grilled chicken');
Result: true