From: Andrew Gierth <andrew@tao11.riddles.org.uk>
To: Tom Lane <tgl@sss.pgh.pa.us>
Cc: pgsql-hackers@lists.postgresql.org
Subject: Re: SQL-spec incompatibilities in similar_escape() and related stuff
Date: Mon, 13 May 2019 19:39:14 +0100
Message-ID: <87d0kmfbpq.fsf@news-spur.riddles.org.uk> (raw)
In-Reply-To: <4486.1557769997@sss.pgh.pa.us>
References: <14047.1557708214@sss.pgh.pa.us>
<8736lihni6.fsf@news-spur.riddles.org.uk>
<87v9yeg69c.fsf@news-spur.riddles.org.uk>
<87k1eufem8.fsf@news-spur.riddles.org.uk>
<4486.1557769997@sss.pgh.pa.us>
>>>>> "Tom" == Tom Lane <tgl@sss.pgh.pa.us> writes:
Tom> Hmm. Oddly, you can't fix it by adding parens:
Tom> regression=# select 'foo' similar to ('f' || escape) escape escape from (values ('oo')) v(escape);
Tom> psql: ERROR: syntax error at or near "escape"
Tom> LINE 1: select 'foo' similar to ('f' || escape) escape escape from (...
Tom> ^
Tom> Since "escape" is an unreserved word, I'd have expected that to
Tom> work. Odd.
Simpler cases fail too:
select 'f' || escape from (values ('o')) v(escape);
psql: ERROR: syntax error at or near "escape"
select 1 + escape from (values (1)) v(escape); -- works
select 1 & escape from (values (1)) v(escape); -- fails
in short ESCAPE can't follow any generic operator, because its lower
precedence forces the operator to be reduced as a postfix op instead.
Tom> The big picture here is that fixing grammar ambiguities by adding
Tom> precedence is a dangerous business :-(
Yeah. But the alternative is usually reserving words more strictly,
which has its own issues :-(
Or we could kill off postfix operators...
--
Andrew (irc:RhodiumToad)
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To: pgsql-hackers@postgresql.org
Cc: andrew@tao11.riddles.org.uk, tgl@sss.pgh.pa.us, pgsql-hackers@lists.postgresql.org
Subject: Re: SQL-spec incompatibilities in similar_escape() and related stuff
In-Reply-To: <87d0kmfbpq.fsf@news-spur.riddles.org.uk>
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