如果某些输入参数可以为 NULL 或为 空, 并且在这种情况下应被忽略,则最好根据用户输入动态地构建整个语句- 并完全省略各自的WHERE
/ORDER BY
子句。
关键是在此过程中正确,安全(优雅地)处理NULL和空字符串。对于初学者来说,这search_term <>''
您需要对PL / pgsql有深入的了解,否则您可能会陷入困境。您的案例的示例代码:
CREATE OR REPLACE FUNCTION my_func(
_search_term text = NULL -- default value NULL to allow short call
, _publication_date_query date = NULL
-- , more parameters
)
RETURNS SETOF articles AS
$func$
DECLARE
sql text;
sql_order text; -- defaults to NULL
BEGIN
sql := concat_ws(' AND '
,'SELECT * FROM articles WHERE status <> ''DELETED''' -- first WHERE clause is immutable
, CASE WHEN _search_term <> '' THEN '$1 @@ textsearchable_index_col' END -- ELSE NULL is implicit
, CASE WHEN _publication_date_query <> '' THEN 'publication_date > $2' END -- or similar ...
-- , more more parameters
);
IF search_term <> '' THEN -- note use of $1!
sql_order := 'ORDER BY ts_rank_cd(textsearchable_index_col, $1) + GREATEST(0,(-1*EXTRACT(epoch FROM age(last_edited)/86400))+60)/60 DESC';
END IF;
RETURN QUERY EXECUTE concat_ws(' ', sql, sql_order, 'LIMIT 500')
USING to_tsquery(_search_term || ':*') -- $1 -- prepare ts_query once here!
, _publication_date_query -- $2 -- order of params must match!
-- , more parameters
;
END
$func$ LANGUAGE plpgsql;
我为函数参数添加了默认值,因此您可以忽略在调用中不适用的参数。喜欢:
SELECT * FROM my_func(_publication_date_query => '2016-01-01');