Re: Error-safe user functions - Mailing list pgsql-hackers

From David G. Johnston
Subject Re: Error-safe user functions
Date
Msg-id CAKFQuwYdQqQru9tpMpY4JpCEJ8OeN8kwmBG6DY2QyzE+5znA6Q@mail.gmail.com
Whole thread Raw
In response to Re: Error-safe user functions  (Andrew Dunstan <andrew@dunslane.net>)
Responses Re: Error-safe user functions  (Tom Lane <tgl@sss.pgh.pa.us>)
List pgsql-hackers
On Wed, Dec 7, 2022 at 8:04 AM Andrew Dunstan <andrew@dunslane.net> wrote:

On 2022-12-07 We 09:20, Tom Lane wrote:
> Andrew Dunstan <andrew@dunslane.net> writes:
>> Perhaps we should add a type in the regress library that will never have
>> a safe input function, so we can test that the mechanism works as
>> expected in that case even after we adjust all the core data types'
>> input functions.
> I was intending that the existing "widget" type be that.  0003 already
> adds a comment to widget_in saying not to "fix" its one ereport call.


Yeah, I see that, I must have been insufficiently caffeinated.


>
> Returning to the naming quagmire -- it occurred to me just now that
> it might be helpful to call this style of error reporting "soft"
> errors rather than "safe" errors, which'd provide a nice contrast
> with "hard" errors thrown by longjmp'ing.  That would lead to naming
> all the variant functions XXXSoft not XXXSafe.  There would still
> be commentary to the effect that "soft errors must be safe, in the
> sense that there's no question whether it's safe to continue
> processing the transaction".  Anybody think that'd be an
> improvement?
>
>                       


I'm not sure InputFunctionCallSoft would be an improvement. Maybe
InputFunctionCallSoftError would be clearer, but I don't know that it's
much of an improvement either. The same goes for the other visible changes.


InputFunctionCallSafe -> TryInputFunctionCall

I think in create type saying "input functions to handle errors softly" is an improvement over "input functions to return safe errors".

start->save->finish describes a soft error handling procedure quite well.  safe has baggage, all code should be "safe".

fmgr/README: "Handling Non-Exception Errors" -> "Soft Error Handling"

"typical safe error conditions include" -> "error conditions that can be handled softly include"

(pg_input_is_valid) "input function has been updated to return "safe' errors" -> "input function has been updated to soft error handling"


Unrelated observation: "Although the error stack is not large, we don't expect to run out of space." -> "Because the error stack is not large, assume that we will not run out of space and panic if we are wrong."?

David J.

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