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Database-Administration.md

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Database Administration

⚠️ This page has not been maintained for a long time

Database dump and restore

Don't forget to backup the database before doing mass changes. You can create a script for that purpose.

MongoDB dump script

#!/bin/sh
# Usage :
# - Edit this file to match the setup of the project
# - Copy this file to /etc/cron.hourly/
target="/path/to/db/backupdir"
mkdir -p $target
mongodump -o $target/mongodb_`/bin/date +%y%m%d-%H:%M`

You can copy this script to /etc/cron.hourly/mongodb-dump for an hourly automated backup.

MySQL dump script

#!/bin/sh
# Usage :
# - Edit this file to match the setup of the project
# - Copy this file to /etc/cron.hourly/
db_name=damasdb
db_user=damas
db_pass=XXXXXXXX
target="/path/to/db/backupdir"
mkdir -p $target
/usr/bin/mysqldump -u$db_user -p$db_pass $db_name | /bin/bzip2 > $target/${db_name}_`/bin/date +%y%m%d-%H:%M`.sql.bz2

JSON dump and restore

Dump from Mongodb

mongoexport --jsonArray -d node -c node > db.json
Restore a JSON dump using Python:
#!/bin/python
#
# put your server URL here,
# then call with
# python damas-restore.py <db.json>
#
import damas
import json
import sys

project = damas.http_connection('http://localhost:8092/api')
file = open(sys.argv[1],"r")
j = json.loads(file.readline())
i = 0
while i < len(j):
    project.create(j[i:i+50])
    i = i+50
    print i,"/",len(j)

Database Queries Examples

MongoDB: list the 10 last modified files

db.node.find({file:{$exists:true}}).sort({time:-1}).limit(10)

MongoDB: Update some file synchonization flags on PSD files

In a MongoDB shell, this will print all your files having the .psd file extension:

db.node.find({file:/.*.psd/}).forEach(function(n){print(JSON.stringify(n))})

Update the files, for example removing some sync flags:

db.node.update({file:/.*.psd/}, {$unset:{dmn_angouleme:1, pipangai:1, dream_wall:1}}, {multi:true})

depending on MongoDB version you have different syntaxes and options available https://docs.mongodb.org/manual/reference/method/db.collection.update/

MongoDB: Mass-change a key type

Context: due to issue #91 the protocol was changing some timestamps values from Integers to Strings during their transfer. To list every String time key:

db.node.find({time: {$type: 2}});

Then we convert their type back to Integers. Warning, we use NumberLong, which is encoded using 64 bits instead of NumberInt:

db.node.find({time:{$type:2}}).forEach(function(obj){obj.time = NumberLong(obj.time); db.node.save(obj) })

MySQL: Invert graph edges direction

You may need to invert the direction of the edges. This was useful for us to migrate our data from the MySQL scheme in the 2.3 version before importing to the newer MongoDB scheme

UPDATE link SET src_id=(@temp:=src_id), src_id = tgt_id, tgt_id = @temp;

Miscelaneous

Add every file of the repository recursively

In a shell with the damas command line interface:

find . -type f -exec damas add {} \;