ONE_LINE

jsonb

https://nandovieira.com/using-postgresql-and-jsonb-with-ruby-on-rails

jsonb = [1]avoids reparsing, [2]supports indexing, [3] no key ordering

hstore = [1]not allow a nested structure, [2]store as strings, require type coercion

jsonb is better than hstore

PSQL search

index = [1]use b tree, [2]avoid sequential scan

GIN (Generalized Inverted Index) = [1]use for array or hash, [2] build value -> where

Delete & destroy for association

1. delete 沒有 dependent: :destroy只清空*_id

2. delete 有 dependent: :destroy皆刪除record

3. destroy 不論有無dependent: :destroy皆刪除record

destroy(*id)
destroy_all()