Re: Microvacuum for gist. Question about GISTPageOpaqueData flag

On 07/27/2015 06:46 PM, Teodor Sigaev wrote:
>> I need an advice, what would be better:
>> - to add new flag like F_HAS_GARBAGE,
>> - or to delete all mentions of F_TUPLES_DELETED and use it in gist microvacuum.
>
> According to commit message:
> commit 2effb72e682a7dbdc9a8a60a80c22ec1fa9d8079
> Author: Heikki Linnakangas <heikki.linnakangas@iki.fi>
> Date:   Fri Nov 7 15:03:46 2014 +0200
> ..
>       The code that generated a record to clear the F_TUPLES_DELETED flag hasn't
>       existed since we got rid of old-style VACUUM FULL. I kept the code that sets
>       the flag, although it's not used for anything anymore, because it might
>       still be interesting information for debugging purposes that some tuples
>       have been deleted from a page.
> ..
>
> If Heikki doesn't change his opinion then introduce new flag. Although I don't
> think that we need to keep F_TUPLES_DELETED.

It's certainly not needed for anything at the moment, although 
conceivably we might reintroduce code that needs it in the future. There 
are plenty of flag bits available, so let's use a new flag. If there was 
a shortage, I wouldn't blink reusing F_TUPLES_DELETED.

- Heikki