Hello Charles,
> Went through the documents listed by you, and they are helpful!
> It seems the main purpose of extension pg_protobuf is to parse
> a protobuf struct and return the decoded field. May I ask how these kinds
> of extensions are used in postgreSQL (or in other words, the scenarios to
> use these plugins)?
There are a few ideas behind all of this.
1) Sometimes people are not quite happy with strict relational schema by
various reasons and prefer something more agile, like XML or JSON. These
formats are indeed more convenient under certain circumstances, for
instance in terms of ease of changing and migrating the schema.
2) One drawback of JSON is redundancy. For instance, you have to store
the names of all document fields. These names don't carry much
information but consume disk space and RAM thus affecting the overall
performance. ZSON extension [1] partially solved this issue. However I
wouldn't call it particularly convenient and the whole approach of
compressing JSON seems to me more like a dirty hack, not a solution. The
problem appeared because of using the wrong data format in the first
place.
3) Unlike JSON, formats like Protobuf or Thrift are binary formats and
most importantly don't store any field names. Thus they don't create a
problem described above. However, PostgreSQL is not capable to access
Protobuf fields out-of-the-box, for instance to index these fields. This
is what pg_protobuf is for.
Hopefully this answers you question. If you have other questions please
don't hesitate to ask!
[1]: https://github.com/postgrespro/zson
--
Best regards,
Aleksander Alekseev
