Re: PoC/WIP: Extended statistics on expressions

On 8/16/21 3:31 AM, Justin Pryzby wrote:
> On 1/22/21 5:01 AM, Justin Pryzby wrote:
>>> In any case, why are there so many parentheses ?
>
> On Fri, Jan 22, 2021 at 02:09:04PM +0100, Tomas Vondra wrote:
>> That's a bug in pg_get_statisticsobj_worker, probably. It shouldn't be
>> adding extra parentheses, on top of what deparse_expression_pretty does.
>> Will fix.
>
> The extra parens are still here - is it intended ?
>

Ah, thanks for reminding me! I was looking at this, and the problem is
that pg_get_statisticsobj_worker only does this:

prettyFlags = PRETTYFLAG_INDENT;

Changing that to

prettyFlags = PRETTYFLAG_INDENT | PRETTYFLAG_PAREN;

fixes this (not sure we need the INDENT flag - probably not).

I'm a bit confused, though. My assumption was "PRETTYFLAG_PAREN = true"
would force the deparsing itself to add the parens, if needed, but in
reality it works the other way around.

I guess it's more complicated due to deparsing multi-level expressions,
but unfortunately, there's no comment explaining what it does.

regards

--
Tomas Vondra
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