Postgresql - 测试记录类型（用于字段或空）

Question

我在处理 plpgsql 和 RECORD 类型时遇到问题。

有谁知道一种方法可以简单地测试返回的 RECORD 类型以了解它是否已设置？

基本模式：

一个函数返回一个 RECORD 并且它可能未设置（即选择返回没有记录）或者它被设置为单个记录。

create or replace function blah()
returns RECORD as $$
declare
  rec RECORD;
begin
   rec := row(null); --Do not want to hear about it not being assigned
   select *, status_field into rec ... ;
   if found then
       raise notice '%', rec.status_field is not null   --prints 't'
   end if

   if not found then
       raise notice '%', rec.status_field is not null   --Throws Error (I just want it to say 'f'
   end if; 
end; $$

create or replace function callblah()
returns text as $$
declare
  rtText text;
  blahRec RECORD;
begin
 blahRed := blah(...);

 -- what test can I do to determine if record is set or not.
 -- Try: if blah is not null then -- nope always returns false for is null and is not null
 -- Try: if blah.status is not null then -- nope throws error on field not existing
 -- What test condition do I need to add here to simply test if record is either (NOT FOUND) or (FOUND where field will exist).
 ...
 end if
end; $$

Answer 1

Ah.. is null 运算符在 RECORD 上是（所有字段都为空），而不是空（所有字段都不为空）。因为我有一些字段 null 我需要做

if blah is null then
   -- No record found
else
   if blah.status is not null then
   -- Record found with field I want
   end if;
end if;