Teodor Sigaev <teo...@sigaev.ru> writes:
>> 2. Unless I'm missing something, contrib/bloom is making no effort
>> to ensure that bloom index pages can be distinguished from other pages
>> by pg_filedump.  That's fine if your expectation is that bloom will always
>> be a toy with no use in production; but otherwise, not so much.  You need
>> to make sure that the last two bytes of the page special space contain a
>> uniquely identifiable code; compare spgist_page_id in SPGiST indexes.

> Now contrib/bloom is a canonical example how to implement yourown index and 
> how 
> to use generic WAL interface. And it is an useful toy: in some cases it could 
> help in production system, patch attached. I'm a little dissatisfied with 
> patch 
> because I had to add unused field to BloomPageOpaqueData, in opposite case 
> size 
> of BloomPageOpaqueData struct equals 6 bytes but special size is MAXALIGNED, 
> so, 
> last two bytes will be unused. If unused field is not a problem, I will push 
> this patch.

Yes, it will mean that the special space will have to be 8 bytes not 4.
But on the other hand, that only makes a difference on 32-bit machines;
if MAXALIGN is 8 then you won't be able to fit anything into those bytes
anyway.  And someday there might be a use for the other two bytes ...
so I'm not particularly concerned by the "wasted space" argument.

                        regards, tom lane

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