Re: proposal: possibility to read dumped table's name from file - Mailing list pgsql-hackers

On 9/21/21 3:28 PM, Alvaro Herrera wrote:
> I definitely agree that we should have two files, one for config and
> another one for filter, since their purposes are orthogonal and their
> formats are likely different; trying to cram the filter specification in
> the config file seems unfriendly because it'd force users to write the
> filter in whatever alien grammar used for the config file.  Also, this
> would make it easier to use a single config file with a bunch of
> different filter files.
> 

+1, that is pretty much excatly what I argued for not too long ago.

> On 2021-Sep-21, Daniel Gustafsson wrote:
> 
>> I'm not convinced that we can/should change or remove a commandline parameter
>> in a coming version when there might be scripts expecting it to work in a
>> specific way.  Having a --filter as well as a --config where the configfile can
>> refer to the filterfile also passed via --filter sounds like problem waiting to
>> happen, so I think we need to settle how we want to interact with this file
>> before anything goes in.
> 
> I think both the filter and the hypothetical config file are going to
> interact (be redundant) with almost all already existing switches, and
> there's no need to talk about removing anything (e.g., nobody would
> argue for the removal of "-t" even though that's redundant with the
> filter file).
> 
> I see no problem with the config file specifying a filter file.
> 
> AFAICS if the config file specifies a filter and the user also specifies
> a filter in the command line, we have two easy options: raise an error
> about the redundant option, or have the command line option supersede
> the one in the config file.  The latter strikes me as the more useful
> behavior, and it's in line with what other tools do in similar cases, so
> that's what I propose doing.
> 
> (There might be less easy options too, such as somehow combining the two
> filters, but offhand I don't see any reason why this is real-world
> useful, so I don't propose doing that.)
> 

Well, I think we already have to do decisions like that, because you can
do e.g. this:

    pg_dump -T t -t t

So we already do combine the switches, and we do this:

    When both -t and -T are given, the behavior is to dump just the
    tables that match at least one -t switch but no -T switches. If -T
    appears without -t, then tables matching -T are excluded from what
    is otherwise a normal dump.

That seems fairly reasonable, and I don't see why not to use the same
logic for combining patterns no matter where we got them (filter file,
command-line option, etc.).

Just combine everything, and then check if there's any "exclude" rule.
If yes, we're done - exclude. If not, check if there's "include" rule.
If not, still exclude. Otherwise include.

Seems reasonable and consistent to me, and I don't see why not to allow
multiple --filter parameters.


regards

-- 
Tomas Vondra
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company