Wietse Venema writes:
Unless I am mistaken, this implements the same functionality as the pipemap table. It queries tables in sequence, not in parallel.
You are correct. The patch consisted of three parts. The first two parts are used to get the basic file structure in place for the joinmap, based on the pipemap. The third part changes the functionality of the new map. The section you quoted was from the second part, copying pipemap to joinmap.
Maybe this was not a handy format to post it; I'll post a new patch tomorrow. Regards, Roel