On a rebuild search could try to lock 10 000 items per transaction. As this can take several hours to index its too large as it leads to the local node indexes getting out of date and could lead to data loss if the search fails or node stops
srvslscle002:~ # grep "save point" catalina.out 2011-12-18 21:03:28,166 INFO IndexManager org.sakaiproject.search.indexer.impl.TransactionalIndexWorker - Indexed 100 documents in 32133387 ms 0.0031120279975466016 documents/second into save point 19 2011-12-19 03:59:06,764 INFO IndexManager org.sakaiproject.search.indexer.impl.TransactionalIndexWorker - Indexed 9978 documents in 24929612 ms 0.40024690316078726 documents/second into save point 20 2011-12-19 08:31:20,325 INFO IndexManager org.sakaiproject.search.indexer.impl.TransactionalIndexWorker - Indexed 9992 documents in 15572889 ms 0.6416278957616663 documents/second into save point 21 srvslscle002:~ #
On a rebuild search could try to lock 10 000 items per transaction. As this can take several hours to index its too large as it leads to the local node indexes getting out of date and could lead to data loss if the search fails or node stops