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doc-exports/docs/dws/dev/dws_06_0098.html
Lu, Huayi a24ca60074 DWS DEVELOPER 811 version 
Reviewed-by: Hasko, Vladimir <vladimir.hasko@t-systems.com>
Co-authored-by: Lu, Huayi <luhuayi@huawei.com>
Co-committed-by: Lu, Huayi <luhuayi@huawei.com>
2023-01-19 13:37:49 +00:00

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Manipulating Queries

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:

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    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:

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    SELECT querytree(to_tsquery('!defined'));
 querytree 
-----------
 T
(1 row)
Parent topic: Additional Features