TSVECTOR

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The TSVECTOR data type stores a list of lexemes, optionally with integer positions and weights. TSVECTOR values are used in full-text search.

Syntax

A TSVECTOR comprises individual lexemes in the form: 'These' 'lexemes' 'are' 'not' 'normalized' 'lexemes.'.

You can optionally add the following to each lexeme:

• One or more comma-separated integer positions:

  'These':1 'lexemes':2 'are':3 'not':4 'normalized':5 'lexemes.':6

• A weight letter (A, B, C, or D), in combination with an integer position:

  'These':1 'lexemes':2B 'are':3 'not':4 'normalized':5A 'lexemes.':6B

  If not specified, a lexeme's weight defaults to D. The lexemes in a TSQUERY and TSVECTOR will only match if they have matching weights. For more information about weights, see the PostgreSQL documentation.

To be usable in full-text search, the lexemes must be normalized. You can do this by using the to_tsvector() built-in function to convert a string input to TSVECTOR:

SELECT to_tsvector('These lexemes are not normalized lexemes.');

       to_tsvector
--------------------------
  'lexem':2,6 'normal':5

Normalization removes the following from the input:

• Derivatives of words, which are reduced using a stemming algorithm.
• Stop words. These are words that are considered not useful for indexing and searching, based on the text search configuration. In the preceding example, "These", "are", and "not" are identified as stop words.
• Punctuation and capitalization.

In the preceding output, the integers indicate that normal is in the fifth position and lexem is in both the second and sixth position in the input.

Examples

For usage examples, see Full-Text Search.

See also

• Full-Text Search
• TSQUERY
• Data Types

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