We have some sites which use solr as an internal search. This is done with the extension ext:solr from DKD. Within the extension there is an install script which provides core for multiple languages.
This is working well on most systems.
Meanwhile we have some bigger sites and as there are some specialities we get problems:
We have sites which import data on a regulary base from outside of TYPO3. To get the solr index up to date we need to rebuild the complete index (at night). But as the site gets bigger the reindex takes longer and longer. And if an error occurs the index is broken the next day.
You could say: no problem just refresh all records, but that would leave information in the index for records which are deleted meanwhile (there is no 'delete' information in the import, except that a deleted record is no longer in the import. So a complete delete of all records before the import (or special marking and explicit deletion afterwards) is necessary.
Anyway, the reindex takes very long and can't be triggered any time. And an error leaves the index incomplete.
In theory there is the option to work with two indices: one which is build up anew and the other one is used for search requests. In this way you always have a complete index, so it might be not up to date. After the new index is build you can swap the indices and rebuild the older one.
That needs to be triggered from inside of TYPO3, but I have not found anything about such a configuration.
Another theoretic option might be a master-slave configuration, but as far as I think about it:
when the index of master is reset to rebuild it, this reset would be synchronized to slave which looses all the information it should provide until the rebuild is complete.
(I think the problem is independent of a specific TYPO3 or solr version, so no version tag)
