[HACKERS] Notes on testing Postgres 10b1

Folks,

I've put together some demos on PostgreSQL 10beta1.  Here's a few
feedback notes based on my experience with it.

Things I tested
----------------

* Logical replication pub/sub with replicating only two tables out of a
12-table FK heirarchy, including custom data types

* Partitioning a log-structured table, including a range type, exclusion
constraint, and foreign key.

* Various Parallel index queries on a 100m-row pgbench table

* Full text JSON search in a books database

* SCRAM authentication for local connections and replication

Positive changes beyond the obvious
-----------------------------------

* Yay defaults with replication on!

* Having defaults on the various _workers all devolve from max_workers
is also great.

* Constraint exclusion + partitioning Just Worked.

Questions
----------

Q1. Why does wal_level default to "replica" and not "logical"?

Q2: I thought we were going to finally change the pg_dump default to
"custom" format in this release?  No?

Problems
--------

P1. On the publishing node, logical replication relies on the *implied*
correspondence of the application_name and the replication_slot both
being named the same as the publication in order to associate a
particular publication with a particular replication connection.
However, there's absolutely nothing preventing me from also creating a
binary replication connection by the same name  It really seems like we
need a field in pg_stat_replication or pg_replication_slots which lists
the publication.


P2: If I create a subscription on a table with no primary key, I do not
recieve a warning.  There should be a warning, since in most cases such
a subscription will not work.  I suggest the text:

"logical replication target relation "public.fines" has no primary key.
Either create one, or set REPLICA IDENTITY index and set the published
relation to REPLICA IDENTITY FULL."


P3: apparently jsonb_to_tsvector with lang parameter isn't immutable?
This means that it can't be used for indexing:

libdata=# create index bookdata_fts on bookdata using gin ((
to_tsvector('english',bookdata)));
ERROR:  functions in index expression must be marked IMMUTABLE

... and indeed it's not:

select proname, prosrc, proargtypes, provolatile from pg_proc where
proname = 'to_tsvector';  proname   |         prosrc         | proargtypes | provolatile
-------------+------------------------+-------------+-------------to_tsvector | jsonb_to_tsvector      | 3802        |
sto_tsvector| to_tsvector_byid       | 3734 25     | ito_tsvector | to_tsvector            | 25          | sto_tsvector
|json_to_tsvector       | 114         | sto_tsvector | jsonb_to_tsvector_byid | 3734 3802   | sto_tsvector |
json_to_tsvector_byid | 3734 114    | s
 

... can we fix that?


-- 
Josh Berkus
Containers & Databases Oh My!