Re: [PATCH] Compression dictionaries for JSONB

Hi hackers,

> 8272749e added a few more arguments to CastCreate(). Here is the rebased patch.

After merging afbfc029 [1] the patch needed a rebase. PFA v10.

The patch is still in a PoC state and this is exactly why comments and
suggestions from the community are most welcome! Particularly I would
like to know:

1. Would you call it a wanted feature considering the existence of
Pluggable TOASTer patchset which (besides other things) tries to
introduce type-aware TOASTers for EXTERNAL attributes? I know what
Simon's [2] and Nikita's latest answers were, and I know my personal
opinion on this [3][4], but I would like to hear from the rest of the
community.

2. How should we make sure a dictionary will not consume all the
available memory? Limiting the amount of dictionary entries to pow(2,
16) and having dictionary versions seems to work OK for ZSON. However
it was pointed out that this may be an unwanted limitation for the
in-core implementation.

[1]:
https://git.postgresql.org/gitweb/?p=postgresql.git;a=commitdiff;h=c727f511;hp=afbfc02983f86c4d71825efa6befd547fe81a926
[2]: https://www.postgresql.org/message-id/CANbhV-HpCF852WcZuU0wyh1jMU4p6XLbV6rCRkZpnpeKQ9OenQ%40mail.gmail.com
[3]: https://www.postgresql.org/message-id/CAJ7c6TN-N3%3DPSykmOjmW1EAf9YyyHFDHEznX-5VORsWUvVN-5w%40mail.gmail.com
[4]: https://www.postgresql.org/message-id/CAJ7c6TO2XTTk3cu5w6ePHfhYQkoNpw7u1jeqHf%3DGwn%2BoWci8eA%40mail.gmail.com

-- 
Best regards,
Aleksander Alekseev