I'm working with a mySQL database located on a separate cluster. Since the changes were few, I was just dumping the whole db and porting it to a fresh database each time. But now changes on the main db are more frequent, so I am looking for something that allows me to just "update" the tables of my existing db after having dumped it from the main site.
I am dumping the db using
mysqldump --master-data -h my_main_server -u my_dump_user -pmy_password mydb > dbdump.sql
How can I use it to "update" my current db?
Since you'd have the tables created already, the dump would fail whilst trying to create them, so for you to be able to execute the dump, you need to drop all the existing tables in the database.
You could have instructions in your dump to do that, so you could execute that command without a problem, or you can just reset the database.
If you really need to update some parts of the db with that dump, you could just comment out all the ALTER and CREATE TABLE instructions and just keep the INSERTS, if that's what you want.
Related
I have a mariaDB database with a rails application.
I'm planning to setup the rails application normally first, then use its user interface to create the database data first, then export those data using mysqldump.
mysqldump -u username -p database_name > data-dump.sql
My question is, if I do migration later, can I still load the mysql dump without facing a problem?
For example, if my migration removes a column, should I create a new database backup using mysqldump again?
And is there anything I need to be careful about schema?
When you do a mysqldump, by default the table create statements are included. They are only excluded if you pass in the --no-create-info flag. Since your migrations are just alterations to the tables, you can be assured that when you load your data later, it will have all of your migrations applied to it up to the point in time your database was dumped.
Furthermore, when you run migrations, rails keeps track of which have been run in the schema_migrations table. So if you roll back to a point in time where you had more migrations afterwards, you can re-run rake db:migrate and only those new ones will run, since that data was all part of your backup.
I have set up a system whose purpose it is to generate incremental dumps of our production data to our data warehouse. "Incremental" in this sense means that we can "synchronize" the production database with our data warehouse every minute or so without having to generate a full dump. Instead, we are just dumping and inserting the new/changed data.
On our replication save, I have set up a system where every relevant table of our production database has one insert TRIGGER and one update TRIGGER. These copy every row which is inserted or updated into an "audit table" in a different schema. This audit schema contains tables with the same structure as the production tables, but no indexes, and by using those TRIGGERs the audit tables will only contain the new or updated rows since the last export.
At the moment I'm using the mysql command line client to do the following for each of these audit tables:
LOCK TABLES table WRITE
SELECT * FROM table
DELETE FROM table
UNLOCK TABLES
I then pipe the output to some other scripts for further processing.
Now this works perfectly fine, however it creates the problem that while the state of every individual table will be consistent, the entire set of tables won't be. For example, if I have a clicks table and an impressions table and there is a 1 minute delay between dumping the former and the latter, the entire dump will be in a state which is inconsistent, obviously.
Now my question is: How do I do the following:
Lock ALL tables
Generate dumps for ALL tables
Delete all data from ALL tables
Unlock tables
I cannot use the mysql command line client because I cannot keep the lock across different sessions, and each table requires a new command. Also, I checked mysqldump which allows dumping multiple tables at a time, but I didn't find a way to delete all data from the tables before releasing the locks.
Any ideas?
To perform the first two points the command could be this one :
mysqldump --lock-all-tables -u root -p DATABASENAME > nameofdumpfile.sql
Since it is not possible to perform step 3 and 4 without releasing the lock, at least with mysqldump utility, why don't copy all the tables into another database (backup db) and then export the dump file from it ?
CREATE DATABASE backupdb;
USE originaldb;
FLUSH TABLES WITH READ LOCK;
keep this prompt(Prompt 1) open and then clone the database from another command prompt(Prompt 2) :
mysqldump --lock-all-tables -u root -p originaldb | mysql -u backup -p password backupdb;
Drop the original database from the Prompt 1 :
USE backupdb;
DROP DATABASE originaldb;
Then restore the empty database back with its original name (note the -d flag ) :
mysqldump --lock-all-tables -u root -p backupdb | mysql -u backup -p password originaldb;
This could be an example of a workaround that you can apply to achieve what you need.
Situation: our production mysql database makes a daily dump into a .sql file. I'd like to keep a shadow database that is relatively up to date.
I know that to create a mysql database from a .sql file, one uses:
mysql -u USERNAME -p DATABASENAME < FILE.SQL
For our db, this took 4-5 hours. Needless to say, I'd like to cut that down, and I'm wondering if there's a way to just update the db with what's new/changed. On Day 2, is there a way to just update my shadow database with the new .sql file dumped from the production db?
MySQL Replication is the way to go.
But, in cases, where that is not possible, use the following procedure:
Have a modifed timestamp column in all your tables and update this value whenever a row is inserted/changed.
Use the following mysqldump options to take the incremental SQL file (this uses REPLACE commands instead of insertcommands, since the existing record will be updated in the backup database).
Keep a timestamp value somewhere placed in the file system. and use it in the where condition. MDFD_DATE is the column name on which you need to filter. On successful backup, update the value stored in the file.
skip-tz-utc prevents MSQL from automatically adjusting the timestamp values, based on your timezone.
mysqldump --databases db1,db2 --user=user --password=password --no-create-info --no-tablespaces --replace --skip-tz-utc --lock-tables --add-locks --compact --where=MDFD_DATE>='2012-06-13 23:09:42' --log-error=dump_error.txt --result-file=result.sql
Use the new sql file and run it in your server.
Limitations:
This method will not work if some records are deleted in your database. You need to manually delete them from the backup databases. Otherwise, keep a DEL_FLAG column and update it to 'Y' in production for deleted records and use this condition to delete records in the backup databases.
This problem can be solved using mysql synchronization.
Some links to guide you:
http://www.howtoforge.com/mysql_database_replication
Free MySQL synchronization tool
https://launchpad.net/mysql-proxy
https://www.google.com.br/search?q=mysql+synchronization
I've exported a mysqldump of a database with InnoDB tables and foreign key relationships in them, using the --single-transaction flag (that I read somewhere I should use for InnoDB). No problems.
But when trying to import that dump into another existing database (same database, different server) I get all sorts of errors when trying to drop the tables because it would break the InnoDB relationships.
I also read that I should use foreign_key_checks=0 to avoid this, but this is a server variable, not part of the dump process. So I'm trying to figure out how to automate all this since I have a script that backs up the DB, it was working when all we had were MyISAM tables:
mysqldump -u user -p'password' --single-transaction -q database | ssh user#backup.com mysql -u user -p'password' database
Thanks.
You can dump into a file, add the required SET FOREIGN_KEY_CHECKS=0; in that file, and then feed the file to mysql.
It turns out that the mysqldump file is smart enough to detect that they are InnoDB tables and puts the appropriate comments at the top of the file. My problem was that when I exported through PHPMyAdmin it didn't put the correct comments on the file, hence causing all this trouble.
Thanks for your response.
You can also add to the mysql command line when restoring without editing the original file. This is very useful as mysql backups can become huge, and editing a GB+ file takes lots of CPU time versus adding this to the commandline,
mysql -D YourDatabaseName -u YourUserName -p --init-command="set ##foreign_key_checks=0"<YourBackupDumpFile.sql
I have a mysql dump created with mysqldump that holds all the tables in my database and all their data. However I only want to restore two tables. (lets call them kittens and kittens_votes)
How would I restore those two tables without restoring the entire database?
Well, you have three main options.
You can manually find the SQL statements in the file relating to the backed up tables and copy them manually. This has the advantage of being simple, but for large backups it's impractical.
Restore the database to a temporary database. Basically, create a new db, restore it to that db, and then copy the data from there to the old one. This will work well only if you're doing single database backups (If there's no CREATE DATABASE command(s) in the backup file).
Restore the database to a new database server, and copy from there. This works well if you take full server backups as opposed to single database backups.
Which one you choose will depend upon the exact situation (including how much data you have)...
You can parse out CREATE TABLE kittens|kitten_votes AND INSERT INTO ... using regexp, for example, and only execute these statements. As far as I know, there's no other way to "partially restore" from dump.
Open the .sql file and copy the insert statements for the tables you want.
create a new user with access to only those 2 tables. Now restore the DB with -f (force) option that will ignore the failed statements and execute only those statements it has permission to.
What you want is a "Single Table Restore"
http://hashmysql.org/wiki/Single_table_restore
A few options are outlined above ... However the one which worked for me was:
Create a new DB
$ mysql -u root -p CREATE DATABASE temp_db
Insert the .sql file ( the one with the desired table ) into the new DB
$ mysql -u root -p temp_db < ~/full/path/to/your_database_file.sql
dump the desired table
$ mysqldump -u root -p temp_db awesome_single_table > ~/awesome_single_table.sql
import desired table
$ mysql -u root -p original_database < ~/awesome_single_table.sql
Then delete the temp_db and you're all golden!