Automatic tablespace management in pg_basebackup

Hi,

Manually specifying tablespace mappings in pg_basebackup, especially in environments where tablespaces can come and go, or with incremental backups, can be tedious and error-prone. I propose a solution using pattern-based mapping to automate this process.

So rather than having to specify.

-T /path/to/original/tablespace/a=/path/to/backup/tablespace/a -T /path/to/original/tablespace/b=/path/to/backup/tablespace/b

And then coming up with a new location to map to for the subsequent incremental backups, perhaps we could have a parameter (I’m just going to choose M for “mapping”), like so:

-M %p/%d_backup_1.1

Where it can interpolate the following values:
%p = path
%d = directory
%l = label (not sure about this one)


Using the -M example above, when pg_basebackup finds:

/path/to/original/tablespace/a
/path/to/original/tablespace/b

It creates:

/path/to/original/tablespace/a_backup_1.1
/path/to/original/tablespace/b_backup_1.1


Or:

-M /path/to/backup/tablespaces/1.1/%d

Creates:

/path/to/backup/tablespaces/1.1/a
/path/to/backup/tablespaces/1.1/b


Or possibly allowing something like %l to insert the backup label.

For example:

-M /path/to/backup/tablespaces/%f_%l -l 1.1

Creates:

/path/to/backup/tablespaces/a_1.1
/path/to/backup/tablespaces/b_1.1


This of course would not work if there were tablespaces as follows:

/path/to/first/tablespace/a
/path/to/second/tablespace/a

Where %d would yield the same result for both tablespaces.  However, this seems like an unlikely scenario as the tablespace name within the database would need to be unique, but then requires them to use a directory name that isn't unique.  This could just be a scenario that isn't supported.

Perhaps even allow it to auto-increment a version number it defines itself.  Maybe %v implies “make up a version number here, and if one existed in the manifest previously, increment it”.

  -T /Users/thombrown/Development/tablespaces/ts_c=/Users/thombrown/Development/backups/tablespaces/1.5/backup_ts_c

  -T /Users/thombrown/Development/tablespaces/ts_d=/Users/thombrown/Development/backups/tablespaces/1.5/backup_ts_d

  -T /Users/thombrown/Development/backups/tablespaces/1.4/ts_c=/Users/thombrown/Development/backups/tablespaces/2.0_combined/ts_c

  -T /Users/thombrown/Development/backups/tablespaces/1.4/ts_d=/Users/thombrown/Development/backups/tablespaces/2.0_combined/ts_d

pg_combinebackup

  -M /Users/thombrown/Development/backups/tablespaces/%v_combined/%d

  -o /Users/thombrown/Development/backups/%v_combined/%d

  /Users/thombrown/Development/backups/{1.0_full,1.1,1.2,1.3,1.4}/data