Let me try to clarify, as I still think we are talking about different things.
The version marker on a file is the oldest format version whose structure that file actually uses. A file labeled V3 contains a structure a V2 reader cannot correctly parse, or a semantic change it will get wrong. There is no partial-success path for a V2 reader on that file. (I believe this is the point Micah was trying to probe.) If a V2 reader could read it at all, labeling it V3 would be incorrect; the writer should have labeled it V2. The file becomes V3 when it contains a breaking change that older readers cannot handle, causes incorrect results, or that they would mishandle without a clear error. That is why a new encoding does not, by itself, bump the file version. A V2 reader can see an encoding or logical type it does not understand and fail on that column. Separately, “this engine supports V3” is a claim about the reader, not a stamp on every file that uses a V3-owned feature. A V3 reader is expected to handle the V3 bundle (including encodings that may also appear as preview in V2 files) by default. The encoding is owned by V3; the file is only V3 if it also contains the breaking change. If anyone has had different interpretations please let me know, but this has been my understanding On Fri, Sep 4, 2026 at 3:32 PM Antoine Pitrou <[email protected]> wrote: > > Hey Ryan, > > Let's get the process issue straight. We voted A, not A + B. Perhaps you > hoped that A implies B, but that is your personal opinion on the topic. > > (as a reminder, you were the one who insisted on a first vote on a very > minimal proposition, before discussing the specifics) > > Having the community accept B implies another discussion and a vote. And > that's the discussion we're having currently, actually, so I don't even > know why you seem to be objecting. > > Regards > > Antoine. > > > > Le 04/09/2026 à 22:02, Ryan Blue a écrit : > > From the doc, here's the point that we've been discussing: > > > >> Readers need a simple mechanism to know whether they support all > features > > they may encounter when reading a specific file. > > > > This is a follow-up to decide between options: > > - Set footer version to 3 (for example) > > - Set footer version to 3+ when preview features are present > > - Set footer version to 3/3+ and record preview feature names > > - Use magic bytes for version - PAR3 > > > > From this, it appears to me that most of us (at least those of us > > discussing it) have been working under the assumption that our vote meant > > using the version by writing it into files. Personally, I think this is > > also a natural conclusion. A reader needs to know what version a file was > > written with in order to decide whether it has guarantees (which is > another > > way to say what's in the versioning doc). > > > > I don't think that this is a dishonest or bad faith argument. > > > > My suggestion to ask the community is really to clarify what we all think > > we voted on. If there was genuine confusion about this then let's talk > > through it. But, again, I don't think that this was unclear to most > people. > > > > Do you agree that it's reasonable to ask what people thought they were > > agreeing to? > > > > Ryan > > > > On Fri, Sep 4, 2026 at 12:26 PM Antoine Pitrou <[email protected]> > wrote: > > > >> > >> Le 04/09/2026 à 20:35, Ryan Blue a écrit : > >>> It sounds like you're suggesting that we don't version data files. I > >> don't > >>> think that makes sense with versioning and I'm pretty sure most people > >> that > >>> voted to use versions would agree with me. > >> > >> The *only* implication of the vote was to move forward with the usage of > >> community-agreed versions (rather than, say, mechanistic calendar-based > >> presets) to signal levels of compatibility between readers and writers. > >> > >> If you wanted the vote to mean something more, then you should have had > >> the vote explicitly mention it. Anything else is dishonest. > >> > >>> Should I start a thread dedicated to asking the > >>> community whether most people thought that "using versions" would mean > >>> writing the version used for a file in the file metadata? > >> > >> No, you should wait for this discussion to happen in the hope of > >> reaching a consensus. > >> > >> Personally, I don't think readers should up front refuse reading a file > >> that has a version number higher than their official compatibility > >> level. Other people (Micah, Will, at least) see to be of the same > opinion. > >> > >> Regards > >> > >> Antoine. > >> > >> > >> > > > > >
