On Thu, May 9, 2019 at 9:30 PM Tom Lane <t...@sss.pgh.pa.us> wrote: > Alex <zhihui.fan1...@gmail.com> writes: > > Someone add some code during backend init which used palloc. but at that > > time, the CurrentMemoryContext is PostmasterContext. at the end of > > backend initialization, the PostmasterContext is deleted, then the error > > happens. the reason why it happens randomly is before the palloc, there > > are some other if clause which may skip the palloc. > > > I still can't explain why PostmasterContext may have impact "index info" > > MemoryContext sometime, but now I just can't reproduce it (before the > > fix, it may happen in 30% cases). > > Well, once the context is deleted, that memory is available for reuse. > Everything will seem fine until it *is* reused, and then boom! > > The error would have been a lot more obvious if you'd enabled > MEMORY_CONTEXT_CHECKING, which would overwrite freed data with garbage. >
Thanks! I didn't know this before and " once the context is deleted, that memory is available for reuse. Everything will seem fine until it *is* reused". I have enabled enable-cassert now. That is normally turned on in --enable-cassert builds. Anybody who's been > hacking Postgres for more than a week does backend code development in > --enable-cassert mode as a matter of course; it turns on a *lot* of > helpful cross-checks. > > > regards, tom lane >
