Thompsonbry.systap added a comment. By label lookup I assume that you mean materializing (projecting out through a SELECT expression) the actual RDF Values for URIs or Literals that have become bound by the query. In general, join processing can proceed without dictionary materialization and that materialization step is deferred until the variable bindings are projected out. At that point they require scattered IOs against the reverse dictionary index (ID2TERM). This does incur overhead.
There are options to inline the full serialization of URIs and Literals. However this decreases the effective stride of the indices and has a negative impact on join performance. So these things get traded off - join performance for statement indices and join performance for RDF Value materialization when projecting out solutions. Those scatter lookups are much faster against SSD. TASK DETAIL https://phabricator.wikimedia.org/T90116 REPLY HANDLER ACTIONS Reply to comment or attach files, or !close, !claim, !unsubscribe or !assign <username>. EMAIL PREFERENCES https://phabricator.wikimedia.org/settings/panel/emailpreferences/ To: Smalyshev, Thompsonbry.systap Cc: Thompsonbry.systap, Beebs.systap, Haasepeter, Aklapper, Manybubbles, jkroll, Smalyshev, Wikidata-bugs, Jdouglas, aude, GWicke, daniel, JanZerebecki _______________________________________________ Wikidata-bugs mailing list [email protected] https://lists.wikimedia.org/mailman/listinfo/wikidata-bugs
