Re: [GENERAL] pg_dump -s dumps data?!

On 01/31/2012 05:48 PM, Tom Lane wrote:
> Andrew Dunstan<andrew(at)dunslane(dot)net> writes:
>> On 01/30/2012 11:18 PM, Tom Lane wrote:
>>> As I suspected, the behavioral change from 9.1 to HEAD is not
>>> intentional. It is an artifact of commit
>>> 7b070e896ca835318c90b02c830a5c4844413b64, which is almost, but not
>>> quite, entirely broken. I won't enumerate its shortcomings here,
>> I'm perplexed about what you thing the patch does wrong or how it affects this. If I've broken something I'd like to know how, exactly, so I have a chance to fix it.
> Well, it adds a new field to all instances of DumpableObject and then
> leaves it uninitialized in most cases, which is bad style (and unlike in
> the backend, there is no forced zeroing to ensure a consistent value);
> but the proximate cause of the bug is that you put the filtering in the
> wrong place. The way this is supposed to work, or at least used to
> work, is that dump-the-data-or-not is determined by whether
> a TableDataInfo DumpableObject gets created --- see the callers of
> makeTableDataInfo. You didn't follow that convention but instead
> inserted an extra filter test in dumpTableData. The reason that
> depesz's example is not dumping the unwanted config table is that the
> code path in which getExtensionMembership calls makeTableDataInfo isn't
> ever setting the dumpdata flag. Unfortunately that means that config
> table data won't get dumped when it *is* wanted, either. Or worse,
> it means that the data might or might not get dumped depending on
> whether the pg_malloc in makeTableDataInfo is allocating new or recycled
> memory and what happens to be in that memory in the latter case.
>
> Now I'm not entirely sure that we ought to preserve the old code
> structure as-is; it might be more future-proof if we always made
> TableDataInfo objects and then used their dump flags to control whether
> to dump them. (The main potential advantage of that is that we'd deal
> more sanely with dependency chains linking through TableDataInfo
> objects; but I'm not sure there are any such at the moment.) But what
> we've got at the moment is a mess. In any case I think we'd be better
> off without the separate dumpdata field: if we need a flag we should use
> the "dump" flag of the TableDataInfo object.
>
> As far as depesz's actual complaint is concerned, I think the core of
> the problem is that getExtensionMembership is unconditionally asking for
> a config table's data to be dumped, without any consideration of whether
> pg_dump switches ought to filter that. I'm unsure whether we should
> just add more logic there, or instead put the policy logic into
> makeTableDataInfo. The latter might result in less duplicative code,
> but would require more rethinking of getTableData() --- which conditions
> tested there ought to move into makeTableDataInfo?
>
>

Here's a possible patch for the exclude-table-data problem along the
lines you suggest.

cheers

andrew