在 PL/pgSQL 中使用 USING 关键字清理用户输入

Question

这就是我创建search_term 的方式：

    IF char_length(search_term) > 0 THEN
        order_by := 'ts_rank_cd(textsearchable_index_col, to_tsquery(''' || search_term || ':*''))+GREATEST(0,(-1*EXTRACT(epoch FROM age(last_edited)/86400))+60)/60 DESC';
        search_term := 'to_tsquery(''' || search_term || ':*'') @@ textsearchable_index_col';
    ELSE
        search_term := 'true';
    END IF;

我在使用 PLPGSQL 函数时遇到了一些问题：

    RETURN QUERY EXECUTE '
        SELECT
            *
        FROM
            articles
        WHERE
            $1 AND
            ' || publication_date_query || ' AND
            primary_category LIKE ''' || category_filter || ''' AND
            ' || tags_query || ' AND
            ' || districts_query || ' AND
            ' || capability_query || ' AND
            ' || push_notification_query || ' AND
            ' || distance_query || ' AND
            ' || revision_by || ' AND
            ' || publication_priority_query || ' AND
            ' || status_query || ' AND
            is_template = ' || only_templates || ' AND
            status <> ''DELETED''
        ORDER BY ' || order_by || ' LIMIT 500'
        USING search_term;
    END; $$;

返回错误：

AND 的参数必须是布尔类型，而不是在字符 64 处键入文本

相对于：

        RETURN QUERY EXECUTE '
            SELECT
                *
            FROM
                articles
            WHERE
                ' || search_term || ' AND
                ' || publication_date_query || ' AND
                primary_category LIKE ''' || category_filter || ''' AND
                ' || tags_query || ' AND
                ' || districts_query || ' AND
                ' || capability_query || ' AND
                ' || push_notification_query || ' AND
                ' || distance_query || ' AND
                ' || revision_by || ' AND
                ' || publication_priority_query || ' AND
                ' || status_query || ' AND
                is_template = ' || only_templates || ' AND
                status <> ''DELETED''
            ORDER BY ' || order_by || ' LIMIT 500';
        END; $$;

...这行得通。我错过了什么吗？
我的目标是清理我的用户输入。

Answer 1

如果您的某些输入参数可以是 NULL 或 empty 并且在这种情况下应该被忽略，您最好根据用户输入动态构建整个语句 - 并省略各自的WHERE / ORDER BY 子句完全。

关键是在处理过程中正确、安全（优雅地）处理NULL和空字符串。对于初学者来说，search_term <> '' 是比char_length(search_term) > 0 更智能的测试。见：

• Best way to check for "empty or null value"

而且您需要对 PL/pgSQL 有深入的了解，否则您可能会不知所措。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，因此您可以省略调用中不适用的参数。喜欢：

SELECT * FROM my_func(_publication_date_query => '2016-01-01');

更多：

• Functions with variable number of input parameters
• The forgotten assignment operator "=" and the commonplace ":="

注意concat_ws() 的战略用途。见：

• How to concatenate columns in a Postgres SELECT?

这是一个相关的答案，有很多解释：

• Test for null in function with varying parameters