On Wed, Oct 25, 2023 at 10:06:23PM -0700, Jeff Davis wrote: > Thank you for the report! I was able to reproduce and observe that the > buffer is not marked dirty. > > The call (hashovfl.c:671): > > XLogRegisterBuffer(1, wbuf, REGBUF_STANDARD) > > is followed unconditionally by: > > PageSetLSN(BufferGetPage(wbuf), recptr) > > so if the Assert were not there, it would be setting the LSN on a page > that's not marked dirty. Therefore I think this is a bug, or at least > an interesting/unexpected case. > > Perhaps the registration and the PageSetLSN don't need to happen when > nitups==0?
Hmm. Looking at hash_xlog_squeeze_page(), it looks like wbuf is expected to always be registered. So, you're right here: it should be OK to be less aggressive with setting the page LSN on wbuf if ntups is 0, but there's more to it? For example, it is possible that bucketbuf, prevbuf and wbuf refer to the same buffer, causing is_prim_bucket_same_wrt and is_prev_bucket_same_wrt to be both true. Particularly, if nextbuf and wbuf are the same buffers, we finish by registering twice the same buffer with two different IDs to perform the tuple insertion and the opaque area updates in two steps. And that's.. Err.. not really necessary? I mean, as far as I read this code you could just reuse the buffer registered at ID 1 and update its opaque area if is_prim_bucket_same_wrt is true? -- Michael
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