At Linux Plumbers 2019 Dr Richard Hipp presented a talk about SQLite (https://youtu.be/-oP2BOsMpdo?t=5525 ). One of the slides was titled "Things to discuss" (https://sqlite.org/lpc2019/doc/trunk/slides/sqlite-intro.html/#6 ) and had a few questions: 1. Reliable ways to discover detailed filesystem properties 2. fbarrier() 3. Notify the OS about unused regions in the database file For 1. I think Jan Kara said that supporting it was undesirable for details like just how much additional fsync were needed due to competing constraints (https://youtu.be/-oP2BOsMpdo?t=6063 ). Someone mentioned there was a patch for fsinfo to discover if you were on a network filesystem (https://www.youtube.com/watch?v=-oP2BOsMpdo&feature=youtu.be&t=5525 )... For 2. there was a talk by MySQL dev Sergei Golubchik ( https://youtu.be/-oP2BOsMpdo?t=1219 ) talking about how barriers had been taken out and was there a replacement. In https://youtu.be/-oP2BOsMpdo?t=1731 Chris Mason(?) seems to suggest that the desired effect could be achieved with io_uring chaining. For 3. it sounded like Jan Kara was saying there wasn't anything at the moment (hypothetically you could introduce a call that marked the extents as "unwritten" but it doesn't sound like you can do that today) and even if you wanted to use something like TRIM it wouldn't be worth it unless you were trimming a large (gigabytes) amount of data (https://youtu.be/-oP2BOsMpdo?t=6330 ). However, there were even more questions in the briefing paper (https://sqlite.org/lpc2019/doc/trunk/briefing.md and search for '?') that couldn't be asked due to limited time. Does anyone know the answer to the extended questions and whether the the above is right deduction for the questions that were asked? -- Sitsofe | http://sucs.org/~sits/
