Updated on 2024-01-25 GMT+08:00

Handling TSQuery

GaussDB(DWS) provides functions and operators that can be used to manipulate queries that are already in tsquery type.

  • tsquery && tsquery

    Returns the AND-combination of the two given tsqueries.

  • tsquery || tsquery

    Returns the OR-combination of the two given tsqueries.

  • !! tsquery

    Returns the negation (NOT) of the given tsquery.

  • numnode(query tsquery) returns integer

    Returns the number of nodes (lexemes plus operators) in a tsquery. This function is useful to determine if the query is meaningful (returns > 0), or contains only stop words (returns 0). For example:

     1
     2
     3
     4
     5
     6
     7
     8
     9
    10
    11
    12
    13
    SELECT numnode(plainto_tsquery('the any'));
    NOTICE:  text-search query contains only stop words or doesn't contain lexemes, ignored
    CONTEXT:  referenced column: numnode
     numnode 
    ---------
           0
    (1 row)
    
    SELECT numnode('foo & bar'::tsquery);
     numnode
    ---------
           3
    (1 row)
    
  • querytree(query tsquery) returns text

    Returns the portion of a tsquery that can be used for searching an index. This function is useful for detecting unindexable queries, for example those containing only stop words or only negated terms. For example:

    1
    2
    3
    4
    5
    SELECT querytree(to_tsquery('!defined'));
     querytree 
    -----------
     T
    (1 row)