Re: foreign data wrappers

Le 29/03/2011 13:28, Zheng Yang a écrit :
> Hi guys,
>
>>>
>>> I've briefly gone through the slides. Regarding the 6 callbacks, is that correct to say that a full table scan will always be performed irregardless of the sql statement,
>>> the FDW is blind to the sql query performed, right?
>>
>> Yes, fairly much. If the feed is large you need some way to pass a limit to the foreign side, possibly via table options. I'm fairly sure you won't be able to get it via the SELECT statement.
>>
>
>
> Regarding the previous flickr example, I'm wondering how this 'free text search' function can be done if the FDW is blind to the SELECT statement.
>
> For instance, the following query is to retrieve a photo relevant to 'panda':
>
> SELECT photo FROM flickr_table WHERE search LIKE '%panda%';
>
> In this case, the FDW can only open a connection to flickr web service and return the next 'row' .
> The problem is that there are a huge number of photos in flickr server and retrieving them sequentially is not realistic.
> Any ideas on how this can be done?
>

It probably means that flickr is not a good example of a nice fdw.

--
Guillaume
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