Null value fetched and no indicator defined

[mloskot]

We have restored Oracle builds on Travis CI (#579).

Oracle build is failing due one test failure:
https://travis-ci.org/SOCI/soci/jobs/275269772

-------------------------------------------------------------------------------
String length
-------------------------------------------------------------------------------
/home/travis/build/SOCI/soci/tests/common-tests.h:4213
...............................................................................
/home/travis/build/SOCI/soci/tests/common-tests.h:4213: FAILED:
  {Unknown expression after the reported line}
due to unexpected exception with message:
  Null value fetched and no indicator defined while executing "select str,
  length(str) from soci_test order by length(str)".

The failing test was added by @vadz on 20 July in c6aef12 and I assume it has never been tried against Oracle due to missing build.

Vadim, I'm taking the liberty to pass the issue over to you :-)

[vadz]

Will check, thanks. Looks like a real bug in Oracle backend...

[vadz]

Damn, I had no idea Oracle could be that broken, but apparently it just handles empty strings in the same way as null, see e.g. https://stackoverflow.com/questions/203493/why-does-oracle-9i-treat-an-empty-string-as-null

And this looks impossible to change/work around, so I'll just have to tweak the test to deal with this.

[mloskot]

This is interesting finding. I had no idea.
Yes, tweaking the tests sound like a good idea.

BTW, this reminds me bugs/annoyances between ODBC drivers - there is no way to work around it than if-else if-else test cases.