On Fri, Mar 22, 2024 at 1:22 PM Tomas Vondra <tomas.von...@enterprisedb.com> wrote: > Right, this will happen: > > pg_combinebackup: error: unable to use accelerated copy when manifest > checksums are to be calculated. Use --no-manifest > > Are you saying we should just silently override the copy method and do > the copy block by block?
Yes. > I'm not strongly opposed to that, but it feels > wrong to just ignore that the user explicitly requested cloning, and I'm > not sure why should this be different from any other case when the user > requests incompatible combination of options and/or options that are not > supported on the current configuration. I don't feel like copying block-by-block when that's needed to compute a checksum is ignoring what the user requested. I mean, if we'd had to perform reconstruction rather than copying an entire file, we would have done that regardless of whether --clone had been there, and I don't see why the need-to-compute-a-checksum case is any different. I think we should view a flag like --clone as specifying how to copy a file when we don't need to do anything but copy it. I don't think it should dictate that we're not allowed to perform other processing when that other processing is required. >From my point of view, this is not a case of incompatible options having been specified. If you specify run pg_basebackup with both --format=p and --format=t, those are incompatible options; the backup can be done one way or the other, but not both at once. But here there's no such conflict. Block-by-block copying and fast-copying can happen as part of the same operation, as in the example that I showed, where some files need the block-by-block copying and some can be fast-copied. The user is entitled to specify which fast-copying method they would like to have used for the files where fast-copying is possible without getting a failure just because it isn't possible for every single file. Or to say it the other way around, if there's 1 file that needs to be copied block by block and 99 files that can be fast-copied, you want to force the user to the block-by-block method for all 100 files. I want to force the use of the block-by-block method for the 1 file where that's the only valid method, and let them choose what they want to do for the other 99. -- Robert Haas EDB: http://www.enterprisedb.com
