Re: BUG #16615: Cannot determine type of Date for "is null" expression

From: "David G(dot) Johnston" <david(dot)g(dot)johnston(at)gmail(dot)com>
To: yuanhang <yuanhang(dot)zheng(at)qq(dot)com>
Cc: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, PostgreSQL mailing lists <pgsql-bugs(at)lists(dot)postgresql(dot)org>
Subject: Re: BUG #16615: Cannot determine type of Date for "is null" expression
Date: 2020-09-14 18:29:12
Message-ID: CAKFQuwaYggLSS9Q3fs6wZd7UGGQQtj3bhPazEZqmaDUAxwvSvQ@mail.gmail.com
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On Mon, Sep 14, 2020 at 12:02 AM yuanhang <yuanhang(dot)zheng(at)qq(dot)com> wrote:

> 2. I don’t understand why the type cannot be parsed in T_NullTest. It can
> be parsed when using the SQL below.
>

Equality is a binary operator so the unknown argument can be inferred from
the known one.

Is Null is a unary operator so there is nothing available with which to
infer a type.

David J.

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