Postgres uses ? as an operator; may its JDBC driver allow escaping?

[Mark Rotteveel]

On Mon, 11 Feb 2013 16:10:27 -0500, Lance Andersen - Oracle
<Lance.Andersen at oracle.com> wrote:
> Currently the intent in the JDBC spec is that the ? only be used as a
> parameter marker and at this time there is no plans to change that as I
do
> not see the demand (this is the 1st time this question has ever been
asked
> in 15 years of this spec).  I also just checked the latest ODBC spec and
I
> have not seen them make any changes to escape  the parameter marker.

Clear, so we can conclude that using '?' for anything other than a
parameter placeholder is not allowed (outside of comments or quoted text);
this might be something to state explicitly in the spec (in section 13.2).
 
>> So escaping or an alternative operator would be better. To be a bit
like
>> the JDBC defined escapes you could think about {ve ?} or {ve "?"} (ve
for
>> vendor escape, just made it up). For an alternative operator I think an
>> escape would be preferable to make it clear it is not in the actual
>> PostgreSQL language (say: {qm} or {ve qm} (qm for questionmark)).
> 
> Nothing prevents the Postgres JDBC driver from creating a vendor
specific
> way to accomplish this just care has to be taken in the design so that
it
> will not conflict with potential new features in JDBC going forward.

Predicting the future is hard to do, so designing something now that might
conflict with future JDBC or SQL changes is entirely possible. My
suggestion is that JDBC should define a 'vendor escape' (see above for an
example), where the argument(s) and result of the escape is entirely up to
the vendor.

This vendor escape would be optional, driver vendors should be
discouraged(!) to implement it but they could use it to do non-standard
things (although escaping the ?-operator is the only application that comes
to mind right now). This prevents a general requirement for driver vendors
to implement something that is not useful for them (eg by providing a
standard escape for the question mark), but will provide 1) a way out if
you really need it and 2) a clear guideline from the perspective of JDBC.

This would leave PostgreSQL with various options to implement the escape
for this query:
SELECT * FROM tbl WHERE tbl.data ? 'abc'

Simple question mark escape:
SELECT * FROM tbl WHERE tbl.data {ve qm} 'abc'

or to be more in line with the function escapes:
SELECT * FROM tbl WHERE {ve qm(tbl.data, 'abc')}

or even (although I'd guess that might be a headache to implement in their
parser):
SELECT * FROM tbl WHERE {ve tbl.data qm 'abc'}

Mark