Subject: Re: PoC/WIP: Extended statistics on expressions
To: Justin Pryzby <pryzby@telsasoft.com>
Cc: Dean Rasheed <dean.a.rasheed@gmail.com>, pgsql-hackers@postgresql.org
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From: Tomas Vondra <tomas.vondra@enterprisedb.com>
Message-ID: <58cbfa74-9356-778b-3e10-94e3075c5807@enterprisedb.com>
Date: Mon, 16 Aug 2021 15:19:53 +0200
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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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