Re: BUG #13645: pg_basebackup backup hash index & unlogged table

On Mon, Oct 5, 2015 at 10:37 AM, Bruce Momjian <bruce@momjian.us> wrote:
> On Mon, Sep 28, 2015 at 06:15:24AM +0000, digoal@126.com wrote:
>>    Hash index and unlogged table don't generate XLOG record, when we use
>> pg_basebackup's backup datafile & xlog archive recovery database, unlogged
>> table datafile will purged, and hash index also has unconsistent data page.
>>   Why pg_basebackup not filter the hash index datafile & unlogged table
>> datafile, these file waste net band and backup file's capcity.
>
> We will issue a warning in 9.5 when hash indexes are created.  I am not
> sure why we don't filter out hash indexed and unlogged tables.

basebackup.c does not have much logic yet to see if the file it is
working on is a relation file (this already exists in
filemap.c@isRelDataFile in pg_rewind), and a WAL sender is not
connected to a particular database, which would be needed for pg_class
lookups, so it seems to me that this would be a complicated
infrastructure for a niche use case. Note to mention that perhaps, in
a perhaps-distant day, hash indexes will have WAL support.
--
Michael