Re: PG 15 (and to a smaller degree 14) regression due to ExprEvalStep size

On 8/10/22 9:27 AM, Amit Langote wrote:
> On Wed, Aug 10, 2022 at 3:57 AM Andres Freund <andres@anarazel.de> wrote:
>> One way this code could be drastically simplified is to force all
>> type-coercions to go through the "io coercion" path, which could be
>> implemented as a single execution step (which thus could trivially
>> start/finish a subtransaction) and would remove a lot of the complicated code
>> around coercions.
> 
> Could you please clarify how you think we might do the io coercion
> wrapped with a subtransaction all as a single execution step?  I
> would've thought that we couldn't do the sub-transaction without
> leaving ExecInterpExpr() anyway, so maybe you meant the io coercion
> itself was done using some code outside ExecInterpExpr()?
> 
> The current JsonExpr code does it by recursively calling
> ExecInterpExpr() using the nested ExprState expressly for the
> coercion.

With RMT hat on, Andres do you have any thoughts on this?

Thanks,

Jonathan