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There is a performance bug that makes *everything* slow in versions 6.4.0 and 6.4.1. The problem is fixed in 6.4.2. It is described by SOLR-10130. This is highly version specificspecifica and only applies to VERY old versions, so if you are not running one of the affected versions, don't worry about it. The rest of this document outside of this one paragraph is not specific to ANY version of Solr.
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