TSQUERY

The TSQUERY stores a list of lexemes separated by operators. TSQUERY values are used in .

Syntax

A TSQUERY comprises individual lexemes and operators in the form: 'These' & 'lexemes' & 'are' & 'not' & 'normalized' & 'lexemes.'.

The operators in a TSQUERY are used to . Valid TSQUERY operators are:

• & (AND). Given 'one' & 'two', both one and two must be present in the matching TSVECTOR.
• | (OR). Given 'one' | 'two', either one or two must be present in the matching TSVECTOR.
• ! (NOT). Given 'one' &! 'two', one must be present and two must not be present in the matching TSVECTOR.
• <-> (FOLLOWED BY). Given 'one' <-> 'two', one must be followed by two in the matching TSVECTOR.
  • <-> is equivalent to <1>. You can specify an integer <n to indicate that lexemes must be separated by n-1 other lexemes. Given 'one' <4> 'two', one must be followed by three lexemes and then followed by two in the matching TSVECTOR.

You can optionally add the following to each lexeme:

• One or more weight letters (A, B, C, or D):

  'These' & 'lexemes':B & 'are' & 'not' & 'normalized':A & 'lexemes':B

  If not specified, a lexeme’s weight defaults to D. It is only necessary to specify weights in a TSQUERY if they are also to be used in a comparison. 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 , the lexemes must be normalized. You can do this by using the to_tsquery(), plainto_tsquery(), or phraseto_tsquery() to convert a string input to TSQUERY:

SELECT to_tsquery('These & lexemes & are & not & normalized & lexemes.');

           to_tsquery
--------------------------------
  'lexem' & 'normal' & 'lexem'

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 . In the preceding example, “These”, “are”, and “not” are identified as stop words.
• Punctuation and capitalization.

Examples

For usage examples, see .

See also