Doc update undo partition

[blogh]

Hi,

I noticed that the documentation of undo_partition lacks a mention of dropping triggers and functions. I propose to add it.

I was also quite surprise when I realized the partition where not undone in the order I thought they would. I did a bunch of drop / create on my partitions before playing with the undo function so the "logical" order was not the same as the "creation order" of the partition. I propose to add a warning about that in the undo_partition doc.

Thx for the hard work.
Benoit.

[keithf4]

There are specific undo_partition_time() and undo_partition_id() functions that will undo things in logical order. undo_partition_native() also does things in logical order. These functions only work on partitions made by pg_partman and it states this.

undo_partition is made to work on any partition set, not specifically the ones generated by pg_partman. In order to do logical order, partman would have to know the exact pattern of the partitioning names, which is why the above functions work. In a general case for any partition set, that isn't predictable, so it can only go in whatever order the list returned from pg_inherits returns.

I do have the trigger drop warning in the other functions, so I agree it should be in one you point out too. I will add that to be included in my next commit.

[blogh]

Overall, I agree with your analysis and I think I should have used undo_partition_time() from the start.

I used undo_partition because it didn't have the mention about the triggers. I thought I could just backfill the last child into the parent without removing the triggers (I was just playing around with the tool, it's not a "need" I have). I was very surprised to see the parent growing :) afterwards.

Regarding the order of the Undo, I understand the reason but was also very surprised at first. I got my answer in the code but felt like It would be worth explaining the unpredictability a bit more.

On a different topic: Is it normal that psycopg2 is not a dependency of the pg_partman package in PGDG ? I understand it's not essential but it's surprising none the less to get this message :

postgres@ulbdybbb01:~$ /usr/lib/postgresql/9.5/bin/reapply_indexes.py
Traceback (most recent call last):
  File "/usr/lib/postgresql/9.5/bin/reapply_indexes.py", line 3, in <module>
	import argparse, psycopg2, re, sys, time
ImportError: No module named psycopg2

**EDIT: Packages for ubuntu 14.04 pg 9.4 and 16.04 pg9.5

[keithf4]

I don't maintain any packages for pg_partman, so you'd have to contact the maintainers of those repositories about any dependencies.

[blogh]

Ok thanks !

I'll close this since you plan to add the comments in a future commit.

[df7cb]

Fwiw I'll update the dependency of the Debian package.