Add Raw SQL escape hatch

[k0001]

As much as I don't like having to reach out to unsafe escape hatches, at times it is just necessary to be able to write raw SQL given that Opaleye doesn't support 100% of PostgreSQL. Of course, we should be adding safe support for as many features as possible, but not being able to write raw SQL as a temporal workaround while Opaleye adds support for any missing feature can certainly be a deal-breaker.

I propose adding this as an internal function:

unsafeRawSqlQuery :: String -> Query a

Without this escape hatch, it is many times hard to recommend Opaleye for a large project.

Some issues that can benefit or could have benefited from this: #211 #175 #164 #139 #134 and many others.

[tomjaguarpaw]

A very good idea!

[DiegoNolan]

Any work on this? I want to want to use the @@ operator for text search. Doesn't appear it is supported.

[tomjaguarpaw]

The escape hatch has not been implemented. It's probably much easier to add the @@ than add the escape hatch at this point.

[centromere]

Any work on this? I want to use the UPSERT feature as described in #139.

[tomjaguarpaw]

Same answer as for UPSERT. No one's done the work yet.

[DanBurton]

Bump. Just want to express continued interest in this feature request.

[tomjaguarpaw]

@DanBurton Are you interested in this issue per se, or just in order to achieve #134?

[DanBurton]

@tomjaguarpaw mainly interested in #134 at the moment, but this issue still seems like a good idea.