I wanted to see what error(s) would be reported if "exit" or "continue" is used, in PL/pgSQL, outside of a loop—and in particular if these were reported as syntax errors or runtime errors. There were no surprises with "continue". But I was surprised by this: create procedure p() language plpgsql as $body$ begin exit; end; $body$; It causes the 42601 syntax error: EXIT cannot be used outside a loop, unless it has a label "unless it has a label"? Eh? I Googled this for that message and found this: “Thread: Better testing coverage and unified coding for plpgsql loops”, Tom Lane, 31 December 2017 The message is mentioned. But I couldn't find any opinion about the intention. I tried this (using Version 15.3): create function f(n in int) returns text language plpgsql as $body$ declare v text not null := 'a'; begin <<b1>>begin v := v||'1'; exit b1 when length(v) > n; v := v||'2'; exit b1 when length(v) > n; v := v||'3'; end b1; return v; end; $body$; It completed without error. I tried "select f(1)" and then with the actuals "2" and "99"—and I got the outcomes that the code asks for. In other words, "exit" can, in at least some scenarios, be used to emulate "goto". (Rather like a premature "return" in the middle of a procedure.) What is the rationale for supporting what seems to be on its face this strange functionality? As it happens, Oracle's PL/SQL has a "goto" statement. But PL/pgSQL does not. (I assume that this is because "goto" is considered a bad thing.) But PL/SQL programmers do use it. However, the doc section: "Porting from Oracle PL/SQL" doesn't mention "goto". But "exit <label>" might help. |
