Re: jsonb format is pessimal for toast compression

Peter Geoghegan <pg@heroku.com> writes:
> I'm not surprised that it hasn't beaten HEAD. I haven't studied the
> problem in detail, but I don't think that the "cache awareness" of the
> new revision is necessarily a distinct advantage.

I doubt it's a significant advantage in the current state of the code;
I'm happy if it's not a loss.  I was looking ahead to someday fetching key
values efficiently from large EXTERNAL (ie out-of-line-but-not-compressed)
JSON values, analogously to the existing optimization for fetching text
substrings from EXTERNAL text values.  As mentioned upthread, the current
JSONB representation would be seriously unfriendly to such a thing.
        regards, tom lane