mkroetzsch added a comment. @JanZerebecki I understand what you are saying about what "indexing" means here. Makes sense to me. What you are saying about my example query sounds as if you are planning to implement query execution manually. I hope this is not the case and you can just give the query to Titan to get it answered for you.
You mentioned splitting certain statements with duplicate qualifiers. This changes the structure, and the original structure is no longer represented and can no longer be faithfully recovered. I don't know if this is an issue with the current data (which duplicate qualifiers are actually used?) but it is an issue in general. It also means that with a mere 40 qualifiers (20 properties, each with two values) on one forged statement, I could create a million statements in your index -- a possible DOS attack vector? An alternative technique for handling such cases is to use a special encoding for overflowing values. This is done successfully in some database implementations, but it may mean additional checks during query answering, and depending on how low in the query answering process you can do these checks, they may or may not add significant cost (hence it's a pity that Titan does not support this efficiently out of the box). TASK DETAIL https://phabricator.wikimedia.org/T86278 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, mkroetzsch Cc: Aklapper, Smalyshev, Lydia_Pintscher, Multichill, Magnus, daniel, JeroenDeDauw, JanZerebecki, aude, mkroetzsch, Denny, Sjoerddebruin, Tobi_WMDE_SW, jkroll, Wikidata-bugs, GWicke, Manybubbles _______________________________________________ Wikidata-bugs mailing list Wikidata-bugs@lists.wikimedia.org https://lists.wikimedia.org/mailman/listinfo/wikidata-bugs
