在 postgresql 中使用动态排序字段/顺序有哪些选项? [英] What are my options for using dynamic sort field/order in postgresql?
问题描述
我发现我可以使用动态sql来插入排序字段和排序方向的参数.我还发现将这些参数插入动态sql可以使用USING param1, param2".
I have found that i can use dynamic sql to plug in parameters for the sort field and the sort direction. I have also found that to plug those parameters into the dynamic sql one can use "USING param1, param2".
这是我正在尝试使用的 plpgsql 函数.不幸的是,postgresql 在应该插入排序方向参数的位置抛出错误.
Here is my plpgsql function i am trying to get working. Unfortunately postgresql is throwing an error at the location where the sort direction param is supposed to be interpolated.
CREATE OR REPLACE FUNCTION manager_performance_get_urls_by_crawl_id(
p_account_id character varying(64),
p_crawl_id character varying(64),
p_field character varying(20),
p_direction character varying(20),
p_page integer,
p_total integer
)
RETURNS TABLE(id character varying(64), source_url text, http_status_code integer, ref_cnt integer, utype rec_url_type, total_size numeric, total_time numeric, secured integer, mime_type character varying(100)) AS $BODY$
DECLARE
SQL text := '
SELECT u.id, u.source_url, u.http_status_code, u.ref_cnt, u.utype, u.total_size, u.total_time, u.secured, u.mime_type FROM url AS u
JOIN crawl AS c ON(u.crawl_id = c.id)
JOIN site AS s ON(c.site_id = s.id)
JOIN person AS p ON(s.person_id = p.id)
WHERE p.account_id = $1 AND u.crawl_id = $2
GROUP BY u.id ORDER BY $3 $4 LIMIT $6 OFFSET ($5 * $6);
';
BEGIN
RETURN QUERY EXECUTE SQL USING p_account_id, p_crawl_id, p_field, p_direction, p_page, p_total;
END;
$BODY$ LANGUAGE plpgsql;
返回的错误:
<b>Warning</b>: pg_query_params(): Query failed: ERROR: syntax error at or near "$4"
LINE 7: GROUP BY u.id ORDER BY $3 $4 LIMIT $6 OFFSET ($5 * $...
^
QUERY:
SELECT u.id, u.source_url, u.http_status_code, u.ref_cnt, u.utype, u.total_size, u.total_time, u.secured, u.mime_type FROM url AS u
JOIN crawl AS c ON(u.crawl_id = c.id)
JOIN site AS s ON(c.site_id = s.id)
JOIN person AS p ON(s.person_id = p.id)
WHERE p.account_id = $1 AND u.crawl_id = $2
GROUP BY u.id ORDER BY $3 $4 LIMIT $6 OFFSET ($5 * $6);
CONTEXT: PL/pgSQL function manager_performance_get_urls_by_crawl_id(character varying,character varying,character varying,character varying,integer,integer) line 12 at RETURN QUERY
推荐答案
您不能在这样的查询中使用查询参数来指定 ASC
或 DESC
:>
You cannot use a query parameter to specify ASC
or DESC
in a query like this:
ORDER BY $3 $4
您应该将方向作为 boolean
传递并像这样构造查询:
You should pass the direction as a boolean
and construct the query like that:
sql := 'SELECT ... ORDER BY $3 '
|| CASE WHEN p_ascending THEN 'ASC' ELSE 'DESC' END
|| 'LIMIT ...';
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