RE: Better performance no-throw conversion?

> From: Michael Lewis <mlewis@entrata.com> 
> Sent: Wednesday, September 8, 2021 13:40
> To: Tom Lane <tgl@sss.pgh.pa.us>
> Cc: ldh@laurent-hasson.com; pgsql-performance@postgresql.org
> Subject: Re: Better performance no-throw conversion?
>
> On Wed, Sep 8, 2021 at 11:33 AM Tom Lane <mailto:tgl@sss.pgh.pa.us> wrote:
> "mailto:ldh@laurent-hasson.com" <mailto:ldh@laurent-hasson.com> writes:
> > Some databases such as SQLServer (try_cast) or BigQuery (safe.cast) offer not-throw conversion.
> > ...
> > I couldn't find a reference to such capabilities in Postgres and wondered if I missed it, and if not, is there any
planto add such a feature?
 
>
> There is not anybody working on that AFAIK.  It seems like it'd have
> to be done on a case-by-case basis, which makes it awfully tedious.
>
> Do you just mean a separate function for each data type? I use similar functions (without a default value though) to
ensurethat values extracted from jsonb keys can be used as needed. Sanitizing the data on input is a long term goal,
butnot possible immediately.
 
>
> Is there any documentation on the impact of many many exception blocks? That is, if such a cast function is used on a
datasetof 1 million rows, what overhead does that exception incur? Is it only when there is an exception or is it on
everyrow?
 
>
>

Hello Michael,

There was a recent thread (Big Performance drop of Exceptions in UDFs between V11.2 and 13.4) that I started a few
weeksback where it was identified that the exception block in the function I posted would cause a rough 3x-5x
performanceoverhead for exception handling and was as expected. I identified a separate issue with the performance
plummeting100x on certain Windows builds, but that's a separate issue.
 

Thank you,
Laurent.