Manipulating Queries

Updated on 2024-09-30 GMT+08:00

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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:

     
        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

SELECT numnode('foo & bar'::tsquery);
 numnode
---------
       3

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:

     
        SELECT querytree(to_tsquery('!defined'));
 querytree 
-----------
 T
(1 row)

Parent topic: Additional Features

Previous topic: Manipulating tsvector

Next topic: Rewriting Queries

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