Re: [PATCH] Compression dictionaries for JSONB

Hi Simon,

Many thanks for your feedback!

I'm going to submit an updated version of the patch in a bit. I just
wanted to reply to some of your questions / comments.

> Dictionaries have no versioning. [...]

> Does the order of entries in the dictionary allow us to express a priority? i.e. to allow Huffman coding. [...]

This is something we discussed in the RFC thread. I got an impression
that the consensus was reached:

1. To simply use 32-bit codes in the compressed documents, instead of
16-bit ones as it was done in ZSON;
2. Not to use any sort of variable-length coding;
3. Not to use dictionary versions. New codes can be added to the
existing dictionaries by executing ALTER TYPE mydict ADD ENTRY. (This
also may answer your comment regarding a limit on SQL statement size.)
4. The compression scheme can be altered in the future if needed.
Every compressed document stores algorithm_version (1 byte).

Does this plan of action sound OK to you? At this point it is not too
difficult to make design changes.

--
Best regards,
Aleksander Alekseev