在开始和结束时动态创建数组

Question

如何在PostgreSQL中动态创建数组？

考虑这个,例如:

CREATE OR REPLACE FUNCTION fun( )
RETURNS SETOF void AS
$BODY$
DECLARE

i numeric;

BEGIN

 FOR i in 1..10   LOOP
     //I have to create an array as 
     arr1[] ,arr2[] ... based on length
 END LOOP;
END;

$BODY$
LANGUAGE plpgsql

Answer 1

为此目的有一个特殊功能 - array_fill:

postgres=# select array_fill(0, ARRAY[10]);
      array_fill       
-----------------------
 {0,0,0,0,0,0,0,0,0,0}
(1 row)

postgres=# select array_fill('Hello'::text, ARRAY[10]);
                          array_fill                           
---------------------------------------------------------------
 {Hello,Hello,Hello,Hello,Hello,Hello,Hello,Hello,Hello,Hello}
(1 row)

postgres=# select array_fill(0, ARRAY[3,3]);
        array_fill         
---------------------------
 {{0,0,0},{0,0,0},{0,0,0}}
(1 row)

在PL/pgSQL中(但对于大型数组(超过100个项目)来说速度要慢得多:

DO $$
DECLARE
result int[] = '{}';
BEGIN
  FOR i IN 1..10
  LOOP
    result := result || 0;
  END LOOP;
  RAISE NOTICE '%', result;
END;
$$;