Re: Yet another fast GiST build

On 13 January 2021 20:04:10 EET, Heikki Linnakangas <hlinnaka@gmail.com> wrote:
>
>
>On 13 January 2021 13:53:39 EET, Heikki Linnakangas <hlinnaka@iki.fi> wrote:
>>Looks like the LSN on the page is not set to GistBuildLSN as expected.
>>Weird.
>>
>>Thorntail is a sparc64 system, so little-endian, but the other
>>little-endian buildfarm members are not reporting this error. Any idea
>>what might be going on?
>
>Status update on this: I am building Postgres in a qemu sparc64 emulated virtual machine, hoping to be able to
reproducethis. It's very slow, so it will take hours still to complete. 
>
>I don't think this is a problem with the test, or with the new pageinspect functions, but a genuine bug in the gist
building code. Or there is something special on that animal that causes the just-created index pages to be dirtied. It
doesseem to happen consistently on thorntail, but not on other animals. 

Ah, silly me. Thorntail uses "wal_level=minimal". With that, I can readily reproduce this.

I'm still not sure why it happens, but now it should be straightforward to debug.

- Heikki