I am surprised by the level of quoting seemingly required by org-mode to pass a variable to psql in :cmdline

The following works:

#+PROPERTY: header-args:sql :engine postgresql :dbhost  my.host :database mydb :dbuser me

#+PROPERTY: header-args:sql+ :tangle no :results table :exports both

#+BEGIN_SRC sql :cmdline "-v this=\\'that\\'"

select :this as this

#+END_SRC

#+RESULTS:

| this |

|------|

| that |

However, I found no other quote/escape combination to work.  At first I expected to work:

:cmdline "-v this=\'asdf\'"

… but it is an error.

Is this expected and consistent with other emacs behavior? 

Is there another, perhaps simpler, way to pass variables to postgresql  code block in org ob-sql?

Thanks,

Malcolm