Alex <zhihui.fan1213@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.