Re: Proposal for Allow postgresql.conf values to be changed via SQL

From: Robert Haas <robertmhaas(at)gmail(dot)com>
To: Amit kapila <amit(dot)kapila(at)huawei(dot)com>
Cc: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Fujii Masao <masao(dot)fujii(at)gmail(dot)com>, "pgsql-hackers(at)postgresql(dot)org" <pgsql-hackers(at)postgresql(dot)org>, Dimitri Fontaine <dimitri(at)2ndquadrant(dot)fr>, "cedric(at)2ndquadrant(dot)com" <cedric(at)2ndquadrant(dot)com>, Greg Smith <greg(at)2ndquadrant(dot)com>, Josh Berkus <josh(at)agliodbs(dot)com>, Magnus Hagander <magnus(at)hagander(dot)net>, Christopher Browne <cbbrowne(at)gmail(dot)com>, Alvaro Herrera <alvherre(at)2ndquadrant(dot)com>
Subject: Re: Proposal for Allow postgresql.conf values to be changed via SQL
Date: 2012-11-30 19:39:17
Message-ID: CA+Tgmob4Z_oVBOBENqJtG3U2C09Fj0PyhHb0fFX3XKWWtReMeQ@mail.gmail.com
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On Wed, Nov 28, 2012 at 9:47 AM, Amit kapila <amit(dot)kapila(at)huawei(dot)com> wrote:
> 5. PERSISTENT Keyword is added to the reserved keyword list. As it was giving some errors given below while parsing gram.y
> 15 shift/reduce conflicts .

Allow me to be the first to say that any syntax for this feature that
involves reserving new keywords is a bad syntax.

The cost of an unreserved keyword is that the parser gets a little
bigger and slows down, but previous experimentation shows that the
effect is pretty small. However, adding a new reserved keyword breaks
user applications. It is hardly difficult to imagine that there are a
decent number of users who have columns or PL/pgsql variables called
"persistent". Let's not break them. Instead, since there were
multiple proposed syntaxes for this feature, let's just pick one of
the other ones that doesn't have this problem.

--
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company

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