• Data Warehouse Service

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  5. Additional Features
  6. Manipulating Queries

Manipulating Queries

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
    SELECT numnode('foo & bar'::tsquery);
  • 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'));
    (1 row)