Some days back, i was having an issue whilst activating the PL/Tcl extension/language on PostgreSQL. Luckily, it was possible with the help from Mauricio Cortes, a guy from the Facebook group PostgreSQL Server. Let's first see what is TCL package. "PL/Tcl is a loadable procedural language for the PostgreSQL database system that enables the Tcl language to be used to write functions and trigger procedures." - PostgreSQL This facilitates us to load the module and unload it if same is not being used. You can also activate it for a particular user.
Initially, after installing the package postgresql95-tcl, as per the documentation, i made a "create extension" but same was returning the error " ERROR: could not open extension control file "/usr/pgsql-9.5/share/extension/pltcl.control : No such file or directory" I also noticed that the file pltcl.control is not present. The guy recommended me to try out a "create language" instead of "create extension" and it works!!.
How silly it may found that, on the official documentation, it was mentioned that the create language has been deprecated and now the create extension is being used. I immediately understand that i was using a bad repository. I would advice to use the official rpm file from the official website yum.postgresql.org.
Lets see how to activate it:
1.Simply fire a yum install postgresql95-tcl Make sure that you are using the right repo (https://www.postgresql.org/download/linux/redhat/) to be able to use the create extension
2.After login, you can verify same with the command \dx to have a list of installed extensions or \dx+ to have more details about the object
3. Now, here is the catch, if you are using PostgreSQL having the version older than 9.5, this should be activated with a create language pltcl; otherwise if its version 9.5 or beta 9.6, you can use a create extension pltcl;.
After some more research i notice that the advantage of this feature is that when a create extension is performed for any plugin the dump of the database will also consist of the extension otherwise in older version the Tcl language would not be included in the dump.
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