![]() We need a guess if the database needs to be vacuumed, we can't detect much about it (see better vacuum section below for information), we will just try to use the freelist to detect if big changes have happened in the database and it needs to be shrinked.This approach is actually the best one, but has some glitches: Better vacuum support in SQLite: this is the long term solution.Vacuum on idle: This is the currently taken in count solution.Third it would put someting storage related in update code. First of all there is a feeling that making upgrades slower will cause users to delay them. Vacuum on major upgrade: This would be a good compromise, but has some drawback.Vacuum in background: Possible for small databases, but for databases like places.sqlite that can take one hundred megabytes, is just not feasible.Vacuum with a button: discarded, we don't want users to have to rememeber they should vacuum.Eventually JOURNAL_MODE=OFF could become a solution for mobile. JOURNAL_MODE=MEMORY and SYNC=OFF times 17s, this is the fastest one, but doesnot have any protection against DB corruption, so we are not going to sacrifice that for 5s.įinal choice is to temporary move the journal file to memory while vacuuming, then resetting it back.Ĭould this be a problem for Mobile? Most likely a mobile DB will contain fair less history (they use smaller prefs) and bookmarks, we expect it to be quite smaller.JOURNAL_MODE=OFF and SYNC=FULL times 21s, does not really make a difference.JOURNAL_MODE=MEMORY and SYNC=FULL is a trick we used migrating 3.0 users to 3.5, pulls down time to 22s.JOURNAL_MODE=TRUNCATE and SYNC=FULL is the default, 36s. ![]() There is some option we can tweak to enhance this: Vacuuming an 86MBs DB takes about 36s on a laptop with a relatively slow disk. the time needed to vacuum a database is independent from database status, a just vacuumed database won't take less time to vacuum it again.the database can't be used while a vacuum is running.In fact, because it moves pages around within the file, auto-vacuum can actually make fragmentation worse." it can make fragmentation even worse: "Auto-vacuum does not defragment the database nor repack individual database pages the way that the VACUUM command does.it does not actually defragment the database, it just remove unused space.incremental vacuum can'tbe used for 2 reasons:.vacuum completely regenerates the database, copying page by page from the old database to a new one.vacuum is a slow operation, it takes seconds to vacuum database, depending on its size.make it dependent on user's actions (add UI and manual vacuuming).fix sqlite fragmentation issues app-wide. ![]()
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