Postgres

DEV INSTALL

There may be one or more system postgres'es already installed. That's fine, just make sure they don't start.

sudo emacs -nw /etc/postgresql/(tab-tab)
sudo emacs -nw /etc/postgresql/10/main/start.conf # change auto > manual
sudo emacs -nw /etc/postgresql/9.6/main/start.conf # change auto > manual
sudo service postgres(tab-tab to determine if there are more than one) stop

• use mh to install postgres and libpqxx to /usr/local

mh-install-postgres

• set up a linux user named "postgres"

# On gentoo:
sudo useradd postgres
# On ubuntu:
sudo adduser postgres
# Put the password in private

• set up a data folder where postgres will put all its data and its log

# Standardize on [/home/m/development/postgres], but always consider symlinking to a large/redundant location.
# Here, we are choosing to use a larger RAID drive.
# WARNING NTFS will not let you chown a folder (you'd have to mount the whole thing as the target owner).  
# So on viper, I had to use the tiny primary drive directly, no symlink to ~m/bigdata.  Fuck off.
mkdir /spiceflow/softraid/development/postgres
cd ~/development && ln -s /spiceflow/softraid/development/postgres postgres
sudo chown -R postgres:postgres postgres /spiceflow/softraid/development/postgres
sudo chmod g+x /spiceflow/softraid/development # and any other parent that is missing this bit, so postgres user can cd to its folder

# We must init the data folder as a postgres "database cluster"
su postgres -c '/usr/local/bin/initdb -D /home/m/development/postgres/data'

START SERVER

Use mh-start-postgres to start postgres (if the server is not already running):

mh-start-postgres

ADD A USER + DB

Use mh-add-postgres-db to add a user (aka role) and matching database. The user only has access to that db (best practice). This will prompt for pw.

mh-add-postgres-db [name]
# Add name+pw to private

Readable UNIX epoch

select to_timestamp((json->>'timestamp')::int) at time zone 'utc', * from stockquotes where (json->>'quote')::float < 0.0;

Yes it's that ridiculous. Yes it's really even worse than that.

NOSQL via JSON

BASICS

GORGEOUS POSTGRES JSON QUERY! inject blobs of JSON, then you can crack open the json inside a cell!

   CREATE TABLE stocks (
     id integer NOT NULL,
     board_id integer NOT NULL,
     data jsonb
   );
   INSERT INTO stocks VALUES (1, 1, '{"symbol": "GOOG", "tags": ["hot", "trending"], "owned": true}');

   # returns count of data that HAS the field ingredients
   SELECT count(*) FROM stocks WHERE data ? 'ingredients';

   # ->> will return the property as integer or text (the parsed form of the attribute).
   SELECT * FROM stocks WHERE data->>'owned' = 'true';         # if data.owned == true

   # -> will return the attribute as a JSON object
   SELECT jsonb_array_elements_text(data->'tags') as tag FROM stocks WHERE id = 1;
   # returns the actual tag values, eg:
       tag
       --------------
       Improvements
       Office
       (2 rows)

PARTIAL UPDATE

INSERT INTO mytable(id, json) VALUES ('1', '{"name":"homey","set":{"some_prop": 99}}'); 
UPDATE SET json = 
    jsonb_set(mytable.json, array['set','some_prop'], '88', true)
where json->>'name' = 'homey';

UPSERTS

Upsert example, from SO:

INSERT INTO live_data(rec_id, control_data) VALUES ('1', '{"set":{"some_prop": 99}}'); 

INSERT INTO live_data(rec_id, control_data) 
VALUES ('1', '{"set":{"some_prop": 88}}')
ON CONFLICT (rec_id) DO 
UPDATE SET control_data = 
    jsonb_set(live_data.control_data, array['set','some_prop'], '88', true)
RETURNING *;

INDEXING

   # NEXT: EXPLORE INDEXING!
   https://blog.codeship.com/unleash-the-power-of-storing-json-in-postgres/