Add instruction and one of example on how to test or play with locally.

PLpgSQL/choestelus/README.md

@@ -0,0 +1,63 @@
+Code to Coffee with PL/pgSQL
+---
+
+## Prerequisite
+
+1. postgresql (tested with postgresql 13)
+2. any postgresql client (this example will use `psql`)
+
+## Instructions
+
+Using containerized postgres instance, this example comes with `docker-compose.yml` for setup local DB instance.
+
+```sh
+# make sure port 15432 is not in-use or change port exposed to
+# available unused port
+# consult with lsof manpage on macOS or ss/netstat for more info
+# for example
+# lsof -i :15432
+# ss -tulpn | grep 15432
+
+# 1. cd into directory with current readme, from root of git repository
+cd $(git rev-parse --show-toplevel)/PLpgSQL/choestelus
+
+# 2. bring up postgresql instance
+docker-compose up -d
+
+# 3. assuming psql is available in localhost, run migration ordered by name, descending
+# log below command is output example.
+
+psql -U postgres -h localhost -p 15432 -f ./1_init.sql
+
+# $ psql -U postgres -h localhost -p 15432 -f 1_init.sql
+# Password for user postgres: <refer to docker-compose.yml> which is 'coffee' in this example
+# CREATE TABLE
+# CREATE TABLE
+# CREATE TABLE
+# CREATE FUNCTION
+# CREATE FUNCTION
+# CREATE TRIGGER
+# CREATE TRIGGER
+# INSERT 0 1
+# INSERT 0 1
+
+
+# 4. run insert data migration to test migrated stored function and triggers
+# log below command is output example.
+
+psql -U postgres -h localhost -p 15432 -f ./2_consume_drink.sql
+
+# Password for user postgres: <refer to docker-compose.yml> which is 'coffee' in this example
+# psql:2_consume_drink.sql:1: NOTICE:  can i haz java gulp gulp
+# psql:2_consume_drink.sql:1: NOTICE:  coding from drinked java
+# INSERT 0 1
+# INSERT 0 1
+# INSERT 0 1
+# psql:2_consume_drink.sql:4: NOTICE:  can i haz mocha gulp gulp
+# psql:2_consume_drink.sql:4: NOTICE:  coding from drinked mocha
+# INSERT 0 1
+
+# 5. (optional) try to look around with changes made in affected tables
+psql -U postgres -h localhost -p 15432 -d postgres -c 'select * from public.codes;'
+psql -U postgres -h localhost -p 15432 -d postgres -c 'select * from public.drink_entities;'
+```