Fix XML conversion

[vapaj]

Converting sqltype=xml values into Haskell types seem to fail:

*** Exception: Incompatible {errSQLType = "xml", errSQLTableOid = column number 1 is out of range 0..-1
Nothing, errSQLField = "column number 1 is out of range 0..-1
", errHaskellType = "Text", errMessage = "types incompatible"}

This is because Persistent tries to parse it as PersistText (using the Database.PostgreSQL.Simple.FromField instance of Text), however the oid of xml, 142, does not match the oid's of name, text, char, bpchar or varchar, resulting in an Incompatible error.

To fix this, I simply changed the type from Text to (unknown) ByteString.

Before submitting your PR, check that you've:

• Documented new APIs with Haddock markup
• Added @since declarations to the Haddock

After submitting your PR:

• Update the Changelog.md file with a link to your PR
• Bumped the version number if there isn't an (unreleased) on the Changelog
• Check that CI passes (or if it fails, for reasons unrelated to your change, like CI timeouts)

[parsonsmatt]

I've fixed CI, mind rebasing and trying again?

[parsonsmatt]

Interesting.

So, based on what you're saying - the xml type shouldn't ever have worked, right? So no existing working code should be affected by this change?

[vapaj]

That's right.

[parsonsmatt]

Wonderful, thanks! 😄