Re: BUG #13909: String concat error with CITEXT after 9.5.0 upgrade.

hein(at)bitechsystems(dot)co(dot)za writes:
> m_text = 'test' || isnull(m_text,''); --code breaks here!

ISNULL is a keyword, which I can't really recommend using as a function
name. This example used to accidentally fail to fail before 9.5 because
ISNULL was considered to bind tighter than ||. But now it binds less
tightly, meaning that the first part of the expression is parsed as
(('test' ||) IS NULL), which is not what you meant.

You could fix this with more parentheses:

m_text = 'test' || (isnull(m_text,''));

or by double-quoting the function name so it doesn't look like a keyword:

m_text = 'test' || "isnull"(m_text,'');

but you might be better advised to rename the function.

regards, tom lane