PostgreSQL函數子查詢中不能識別的變量？

Question

工作的解決方案：

CREATE OR REPLACE FUNCTION my_search(tsq tsquery, translation_id integer, lang regconfig, count integer DEFAULT 10, skip integer DEFAULT 0) 
RETURNS TABLE(id int, chapter int, number int, headline text) AS $$ 
     SELECT id, chapter, number, ts_headline($3, text, $1, 'StartSel = <em>, StopSel = </em>'::text) FROM (
      SELECT id, chapter, number, text FROM lyrics 
      WHERE $1 @@ search_text AND translation_id = $2 
      LIMIT $4 OFFSET $5) AS matches; 
$$ LANGUAGE SQL STABLE; 

原件以下問題。

---

我一直在試圖創建存儲這樣的過程PostgreSQL的：

CREATE OR REPLACE FUNCTION my_search(tsq tsquery, translation_id integer, lang text, count integer DEFAULT 10, skip integer DEFAULT 0) 
RETURNS TABLE(id int, chapter int, number int, headline text) AS $$ 
     SELECT id, chapter, number, ts_headline(lang, text, tsq, 'StartSel = <em>, StopSel = </em>') FROM (
      SELECT (id, chapter, number, text) FROM my_texts 
      WHERE tsq @@ search_text AND translation_id = translation_id 
      LIMIT count OFFSET skip) AS matches; 
$$ LANGUAGE SQL STABLE; 

但是當我嘗試將其加載到數據庫中，我得到這個錯誤：

psql:scriptura.pgsql:7: ERROR: column "tsq" does not exist 
LINE 5:   WHERE tsq @@ search_text AND translation_id = tran... 
         ^

看來函數變量確實不會進入子查詢的範圍。我一直在淘寶PostgreSQL文檔，我似乎無法找出原因。任何人都可以弄清楚我的變量會發生什麼？

Answer 1

LANGUAGE SQL只接受位置參數：

CREATE OR REPLACE FUNCTION my_search(tsq tsquery, translation_id integer, lang text, count integer DEFAULT 10, skip integer DEFAULT 0) 
RETURNS TABLE(id int, chapter int, number int, headline text) AS $$ 
     SELECT id, chapter, number, ts_headline($3, text, $1, 'StartSel = <em>, StopSel = </em>') FROM (
      SELECT (id, chapter, number, text) FROM my_texts 
      WHERE $1 @@ search_text AND translation_id = $2 
      LIMIT $4 OFFSET $5) AS matches; 
$$ LANGUAGE SQL STABLE; 

從documentation：

Arguments to the SQL function are referenced in the function body using the syntax $n : $1 refers to the first argument, $2 to the second, and so on. If an argument is of a composite type, then the dot notation, e.g., $1.name , can be used to access attributes of the argument.