The database schema is not a secret. If it helps, I can post it, that's no problem. Is it enough to run ".dump" on a database without data?
----- Original Message ----- From: Keith Medcalf <kmedc...@dessus.com> To: SQLite mailing list <sqlite-users@mailinglists.sqlite.org> Sent: Friday, November 1, 2019, 22:57:02 Subject: [sqlite] DELETE extremely slow On Friday, 1 November, 2019 15:12, Simon Slavin <slav...@bigfraud.org> wrote: >So the slow-down in the DELETE FROM command is caused by a TRIGGER, but >there are no TRIGGERs on DELETE ? I don't understand that. Can someone >explain, please ? The code indicates that they are AFTER DELETE so presumably they are triggers, though they are fkey.abort and .abort, so they may be also the result of the implementation of ON DELETE conditions, which are internally implemented by sub-programs and cannot really be distinguished from triggers without seeing the full schema. You might be able to tell if explain comments were enabled at compile time (SQLITE_ENABLE_EXPLAIN_COMMENTS), though I can't really say whether the extra comments would make it obvious or not without being able to see the actual schema or doing a more detailed analysis of the VDBE code. Foreign key constraints are processed in-line since the default condition is to abort/rollback the entire statement only if the fkey violation count is not zero at the end of the statement execution. If you have ON conditions attached to the foreign key constraint, they are implemented by a sub-program called after the processing of each row rather than inline. This means, for example, that if you have ON DELETE RESTRICT specified against a foreign key constraint that a statement which has no violations will effectively be "half as efficient" as one that does not have ON DELETE RESTRICT because extra constraint will be implemented as a sub-program that will re-check the constraint during statement execution so that an immediate ABORT can be raised ... or at least I think that is how it is implemented. The same applies for ON ... CASCADE or ON ... SET NULL which must be implemented as a sub-program run per-row and is not easily distinguishable from a trigger which implements the same functionality. -- The fact that there's a Highway to Hell but only a Stairway to Heaven says a lot about anticipated traffic volume. _______________________________________________ sqlite-users mailing list sqlite-users@mailinglists.sqlite.org http://mailinglists.sqlite.org/cgi-bin/mailman/listinfo/sqlite-users _______________________________________________ sqlite-users mailing list sqlite-users@mailinglists.sqlite.org http://mailinglists.sqlite.org/cgi-bin/mailman/listinfo/sqlite-users
