===== PostgreSQL/Postgres =====

== init data store ==

''initdb -D /Users/dcai/.local/var/postgres12''

== start sever with data store ==
''postgres -D ~/.local/var/postgres12/''

== create super user ==
''createuser -s postgres''

== update user password ==

''ALTER USER postgres WITH PASSWORD 'xxxxx';''

== Backup ==
<code>pg_dump -h localhost -U postgres -F c -f "~/dbbackup/" dbname</code>

== Restore == 
<code>pg_restore -h localhost -U postgres -d old_db "~/dbbackup/"</code>

== Drop index == 
<code>echo "DROP INDEX mdl_quiz_xxx_idx" | sudo psql -U postgres moodle_19</code>

== Handle large db ==
backup
<code>pg_dump dbname | gzip > filename.gz</code>
restore
<code>gunzip -c filename.gz | psql dbname</code>
<code>cat filename.gz | gunzip | psql dbname</code>