CREATE EXTENSION <name> FROM <old_version> is not supported anymore with
postgres 13. An alternative output is added for pg13 where we basically
error for that statement.
DESCRIPTION: satisfy static analysis tool for a nullptr dereference
During the static analysis project on the codebase this code has been flagged as having the potential for a null pointer dereference. Funnily enough the author had already made a comment of it in the code this was not possible due to us setting the schema name before we pass in the statement. If we want to reuse this code in a later setting this comment might not always apply and we could actually run into null pointer dereference.
This patch changes a bit of the code around to first of all make sure there is no NULL pointer dereference in this code anymore.
Secondly we allow for better deparsing by setting and adhering to the `if_not_exists` flag on the statement.
And finally add support for all syntax described in the documentation of postgres (FROM was missing).
Sait Talha Nisanci
Hadi Moshayedi
Marco Slot
Nils Dijk
Jelte Fennema
Onur TIRTIR
Philip Dubé