Adapt sql for postgres

[anphung]

• Adapt sql for postgres placeholder ? vs $1

[cbusbey]

Hi @anphung,

First of all, apologies for the late response. I try to respond to requests asap, this one got away from me.

It is unfortunate that the sql driver placeholders are not abstracted... In the best interests of longer term planning to support a range of db impls, instead of a conditional block based on the underlying driver, we would rather either use a dep to handle this abstraction, or handle it internally with our own polymorphism (probably the latter). I'll create an issue so that we can track this to be fixed in master.