From: | Peter Eisentraut <peter_e(at)gmx(dot)net> |
---|---|
To: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
Cc: | pgsql-hackers(at)postgreSQL(dot)org |
Subject: | Re: Precedence of standard comparison operators |
Date: | 2015-02-20 20:12:18 |
Message-ID: | 54E79522.1000105@gmx.net |
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Thread: | |
Lists: | pgsql-hackers |
On 2/20/15 2:41 PM, Tom Lane wrote:
> I don't believe there is any practical way for us to generate useful
> warnings here; as I said to Kevin, I don't think that Bison exposes
> sufficient information to detect when a parsing decision was made
> differently than before because of precedence.
We could check if there is a >= or <= as a child of another general
operator. That is already quite unlikely to begin with (except for the
obvious common case I am forgetting right now). We could even do this
in an external module with a hook. Or to be more precise, check whether
the >= or <= was in parentheses, which we could record in the parser.
Neither might be absolutely accurate, but it would at least give users a
list of things to check.
The above would imply that we add these checks before changing the
precedence. Creating a check under the new precendence would be much
harder.
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