Hi Jakub,
For a stable/consistent pagination, ORDER BY is always necessary. Even if data
are constant and statistics of indexes are not refreshed between fetching
different pages, the optimizer can chose different ordering depending on number
of rows to skip and return.
Best Regards
Hugh Williams
Professional Services
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On 24 Mar 2014, at 14:55, Jakub Kotowski <ja...@sindicetech.com> wrote:
> Hello everyone,
>
> what is the recommended way of getting large SPARQL result sets?
>
> Normally one should paginate through the results by LIMIT and OFFSET.
> But that normally requires ORDER BY to get consistent results.
>
> Are there some circumstances under which the ORDER BY would not be
> necessary?
>
> For example, if the dataset is not being updated in the background? Or
> maybe subsequent queries with different LIMITs and OFFSETs could be
> evaluated by different threads which could lead to different natural
> order (?) making the ORDER BY always necessary? In such case, would an
> ORDER BY on a subject URI be inexpensive because of an index?
>
> What would be the recommended way of getting the whole dump of a large
> result set if I have control over the server?
>
> Regards,
>
> Jakub
>
>
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