Better documentation for RIR term?

I have had hard times understanding what RIR rules are while reading
some threads in pgsql-hackers. One example is 'Virtual generated
columns'. I was trying to grep 'RIR rules', when I just started to
read kernel sources. And I only today I finally bumped into this note
in rewriteHandler.c

```
* NOTES
* Some of the terms used in this file are of historic nature: "retrieve"
* was the PostQUEL keyword for what today is SELECT. "RIR" stands for
* "Retrieve-Instead-Retrieve", that is an ON SELECT DO INSTEAD SELECT rule
* (which has to be unconditional and where only one rule can exist on each
* relation).
*

```

Maybe I'm really bad at searching things and nobody before had
problems understanding what RIR stands for. If not, should we enhance
documentation in some way? If yes, what is the proper place?

--
Best regards,
Kirill Reshke