I have DB InnoDb innodb_db_1. I have turned on innodb_file_per_table.
If I go to var/lib/mysql/innodb_db_1/ I will find files table_name.ibd, table_name.frm, db.opt.
Now, I'm trying to copy these files to another DB for example to innodb_db_2(var/lib/mysql/innodb_db_2/) but nothing happened.
But if my DB will be MyIsam, I can copy in such way and everything be ok.
What suggestions to move the DB by copying the file of InnoDb DB?
Even when you use file-per-table, the tables keep some of their data and metadata in /var/lib/mysql/ibdata1. So you can't just move .ibd files to a new MySQL instance.
You'll have to backup and restore your database. You can use:
mysqldump, included with MySQL, reliable but slow.
mydumper, a community contributed substitute for mysqldump, this supports compression and parallel execution and other neat features.
Percona XtraBackup, which is free and performs high-speed physical backups of InnoDB (and also supports other storage engines). This is recommended to minimize interruption to your live operations, and also if your database is large.
Re your comment:
No, you cannot just copy .ibd files. You cannot turn off the requirement for ibdata1. This file includes, among other things, a data dictionary which you can think of like a table of contents for a book. It tells InnoDB what tables you have, and which physical file they reside in.
If you just move a .ibd file into another MySQL instance, this does not add it to that instance's data dictionary. So InnoDB has no idea to look in the new file, or which logical table it goes with.
If you want a workaround, you could ALTER TABLE mytable ENGINE=MyISAM, move that file and its .frm to another instance, and then ALTER TABLE mytable ENGINE=InnoDB to change it back. Remember to FLUSH TABLES WITH READ LOCK before you move MyISAM files.
But these steps are not for beginners. It would be a lot safer for you to use the backup & restore method unless you know what you're doing. I'm trying to save you some grief.
There is an easy procedure to move the whole Mysql InnoDB from pc A to pc B.
The conditions to perform the procedure are:
You need to have innodb_file_per_table option set
You need to be able to make a shutdown of the database
In my case i had to move whole 150Gb MySql database (the biggest table had aprox. 60Gb). Making sqldumps and loading them back was not an option (too slow).
So what I did was I made a "cold backup" of the mysql database (mysql doc) and then simply move files to another computer.
The steps to make after moving the databse are described here dba stackexchange.
I am writing this, because (assuming you are able to follow mentioned conditions) this is by far the fastest (and probalby the easiest) method to move a (large) MySql InnoDb and nobody mentioned it yet.
You can copy MyISAM tables all day long (safely, as long as they are flushed and locked or the server is stopped) but you can't do this with InnoDB, because the two storage engines handle tables and tablespaces very differently.
MyISAM automatically discovers tables by iterating the files in the directory named for the database.
InnoDB has an internal data dictionary stored in the system tablespace (ibdata1). Not only do the tables have to be consistent, there are identifiers in the .ibd files that must match what the data dictionary has stored internally.
Prior to MySQL 5.6, with the introduction of transportable tablespaces, this wasn't a supported operation. If you are using MySQL 5.6, the link provides you with information on how this works.
The alternatives:
use mysqldump [options] database_name > dumpfile.sql without the --databases option, which will dump the tables in the specified database but will omit any DATABASE commands (DROP DATABASE, CREATE DATABASE and USE), some or all of which, based on the combination of options specified, are normally added to the dump file. You can then import this with mysql [options] < dumpfile.sql.
CREATE TABLE db2.t1 LIKE db1.t1; INSERT INTO db2.t1 SELECT * FROM db1.t1; (for each table; you'll have to add any foreign key constraints back in)
ALTER TABLE on each table, changing it to MyISAM, then flushing and locking the tables with FLUSH TABLES WITH READ LOCK;, copying them over, then altering everything back to InnoDB. Not the greatest idea, since you'll lose all foreign key declarations and have to add them back on the original tables, but it is an alternative.
As far as I know, "hot copying" table files is a very bad idea (I've done it two times, and only made it work with MyISAM tables, and i did it only because I had no other choice).
My personal recomendation is: Use mysqldump. On your shell:
mysqldump -h yourHost -u yourUser -pYourPassword yourDatabase yourTable > dumpFile.sql
To copy the data from a dump file to another database, on your shell:
mysql -h yourHost -u yourUser -pYourPassword yourNewDatabase < dumpFile.sql
Check: mysqldump — A Database Backup Program.
If you insist on copying InnoDB files by hand, please read this: Backing Up and Recovering an InnoDB Database
Related
this isn't my exact situation but close enough for description.
On a MySQL 8.0.28 instance on an ubuntu 22.08 server, I have a database 'important' that contains only MyISAM tables. Within MySQL I:
DROP DATABASE important;
then continue to 'do stuff' with other databases etc. Some time later, I decide I want that 'important' database back (without restoring other databases). Luckily I have a physical backup of the MySQL data folder, specifically including the 'important' directory.
If I stop the server, copy the 'important' directory back in place, then restart the server I hoped (and was the case under MySQL 5) that the database would re-appear, but it doesn't.
As far as I can sell, MySQL 5 used to physically scan the directory to look for databases whereas MySQL 8 seems to have a separate idea of what databases exist. To clarify, I am only using MySQL 8.0.28 in this scenario - the backup was made under the same version as I'm restoring to.
My question is, how can I make this database reappear? Perhaps that's "How can I make MySQL 8 rescan its database of databases"?
I think you're in uncharted territory.
It's true that in MySQL 5.x, you could create a schema simply with mkdir, creating a subdirectory under the data directory. Within that directory, each MyISAM table has three files: tablename.MYD, tablename.MYI, and tablename.frm. The frm file has metadata about the table and its columns, so the MyISAM storage engine could discover new tables simply by reading their respective frm file.
This was not possible for InnoDB in 5.x, because InnoDB had an internal data dictionary stored in the ibdata1 tablespace in the data directory. The data dictionary had to maintain duplicate metadata about InnoDB tables.
In MySQL 8.0, they eliminated frm files completely. Tables of all storage engines are managed by the InnoDB data dictionary. There is no interface to the data dictionary besides DDL statements like CREATE/ALTER/DROP. There are several benefits to this change.
This means you can't use external shell commands like mkdir and cp to create schemas and tables. You have to use DDL to communicate to the data dictionary. It's not only stored on disk in the InnoDB tablespace, but it's also cached as objects in the MySQL Server process. Using DDL updates both.
I have not tried this with MyISAM tables (I haven't used MyISAM tables if I can avoid it for over ten years), but in theory you could use CREATE SCHEMA and CREATE TABLE to recreate empty tables that match the definition of the tables you're restoring. Then outside of MySQL, use cp to copy the tables you want to restore over the empty data and index files. I would shut down MySQL Server before doing this, to hopefully avoid any race conditions or conflicting with file caches.
I have no idea if that will work. I would test these steps first on a test instance (not your production instance).
I took a backup of my database from engine yard, which is downloaded in sql.gz File. Since one of the tables of my database is too large, so I want to skip it while restoring it in my local system.
I use gunzip < file_name.sql.gz | mysql -u user_name -p password database name command to restore backup.
You may have identified a solution for this by now but I figured I'd add some insight. The restore operation of MySQL does not currently offer an easy way to exclude a single table from the restore operation, but there are a few options you could consider:
If your local MySQL server offers the 'Blackhole' engine you could use gawk to alter the ENGINE definition for that table when it is created. This would be something like:
gunzip < file_name.sql.gz | gawk -v RS='' '{print gensub(/(CREATE TABLE .[table_to_be_skipped].*) ENGINE=InnoDB/, "\\1 ENGINE=Blackhole", 1)}' | mysql -u user_name -p password database name.
This instructs the database to just pass through the row inserts against this table during the reload. Once the load completes you could modify this back to the InnoDB engine with alter table [table_to_be_skipped] engine=innodb;. The drawback to this would be that you are still downloading and parsing through a larger backup.
Another option would be to use the Awk method described here to create two backup files, one representing the tables and data prior to the excluded table, and another representing everything that follows it. The tricky part here is that if you add tables on either side of the excluded table you would have to update this script. This also has the consequence of having to download and parse a larger backup file but tends to be a bit easier to remember from a syntax perspective.
By far the best option to addressing this would be to simply do a manual backup on your source database that ignores this table. Use a replica if possible, and use the --single-transaction option to mysqldump if you are using all InnoDB tables or consistency of non-InnoDB tables is of minimal importance to your local environment. The following should do the trick:
mysqldump -u user_name -p --single-transaction --ignore-table=[table_to_be_skipped] database name | gzip > file_name.sql.gz
This has the obvious benefit of not requiring any complex parsing or larger file downloads.
Not sure if this will help, but we have documentation available for dealing with database backups - also, you may want to talk to someone from support through a ticket or in #engineyard on IRC freenode.
$ user=jocular; cat ~/list|while read db; do echo rm -vi /var/lib/mysql/$user_$db; done
That is what I came up with but my instructor gave me this feedback :
Removing MySQL databases in this manner can cause catastrophic problems for the MySQL server that can lead to loss of the MySQL server. Remove a database using InnoDB tables in this fashion and attempt to restore it from a backup to learn more.
What would be the safest command to remove the unmapped databases ?
Your instructor is right, InnoDB makes it harder to manipulate tables and databases using shell tools. The reason is that InnoDB manages a "data dictionary" inside the ibdata1 file, which catalogs the databases and tables and which tablespace files they belong in. If you move or rename or delete files in the shell, InnoDB's data dictionary now references out-of-date information, and subsequently trying to use those table names or database names runs into conflicts.
Sort of like when you get a new phone, and you keep getting calls from friends of the former owner of that phone number.
If you use SQL or other MySQL commands to drop the database, InnoDB makes sure to update its data dictionary and keep it in sync with reality.
user=jocular; cat ~/list | while read db; do mysqladmin drop "${user}_${db}" ; done
Mysqladmin prompts you before dropping a database, since there's no undoing that change. But you can also use the -f option to force dropping without prompting. Just be careful you don't drop the wrong database!
Want to copy some big tables which are used very often from main server to local server in production mode ofc.
Is it safe?
Some suggestions, tools are welcome. :)
I'm guessing from asking about MYI tables that all of your tables are MyISAM tables and not InnoDb ones. Each MyISAM table is made up of three files: .frm, .MYD and .MYI they contain the structure, data and index respectively.
People advise against copying these raw files from running systems but I've found that as long as you're sure nothing's writing to the tables then copying them works fine (I've done this more times than I care to remember).
If you're doing this on a replica then just stop replication on the slave before copying. If it's just a single server or the master I'd recommend running FLUSH TABLES WITH READ LOCK before you start copying files, this will prevent any process from writing to the tables. When you're done release the lock with UNLOCK TABLES.
I would always recommend doing a CHECK TABLE on the tables you've copied in this manner. I think this is what I've used in the past mysqlcheck --all-tables --fast --auto-repair
If you're using LVM on the server then taking an LVM snapshot could be another way of getting hold of a clean snapshot.
If you're going to be doing this regularly I'd recommend either using replication to keep the local server up to date or to setup a slave which you can use for taking backups (as it's not the main database there's no problem with you stopping it, dumping tables, etc)
Yes it's alright if you
Shut the mysql server down cleanly before you copy the files, or at least take a global read lock
Take the .frm .MYI and .MYD files at the same time.
Have identical my.cnf and run the same MySQL version on each system
So it's basically ok, but not necessarily a good idea.
If you have different versions of mysql (You can only generally move to a more recent version, not an older one), or are running with a significantly different my.cnf (i.e. any of the fulltext indexing parameters differ, and you have fulltext indexes), you may need to rebuild the table. Rebuilding the table can be done on the destination server with ALTER TABLE blah ENGINE=MyISAM; this might still be a bit faster than a mysqldump / restore.
I need to dump a database from a shared hosting that somehow doesn't have mysqldump installed. In fact, I only have mysql and mysqladmin available from the whole set of MySQL utilities.
Is it doable or I'll need to resort to installing something like phpMyAdmin?
You could use the following methods (from Database Backups in the documentation)
Making Backups by Copying Files
MyISAM tables are stored as files, so it is easy to do a backup by copying files. To get a consistent backup, do a LOCK TABLES on the relevant tables, followed by FLUSH TABLES for the tables. You need only a read lock; this allows other clients to continue to query the tables while you are making a copy of the files in the database directory. The FLUSH TABLES statement is needed to ensure that the all active index pages are written to disk before you start the backup.
FLUSH TABLES WITH READ LOCK;
Closes all open tables and locks all tables for all databases with a read lock until you explicitly release the lock by executing UNLOCK TABLES. This is very convenient way to get backups if you have a file system such as Veritas that can take snapshots in time.
UNLOCK TABLES;
Making Delimited-Text File Backups
To create a text file containing a table's data, you can use:
SELECT * INTO OUTFILE 'file_name' FROM tbl_name
This method works for any kind of data file, but saves only table data, not the table structure.
To reload the output file, use"
LOAD DATA INFILE
how about shutting down the server and copying the datadir itself?
You can get SQLYog. It has a back up database as SQL Dump option for each database.
Anyways,
I had to resort to using the Sypex dumper, a web-based tool for fast (really fast, much faster than phpMyAdmin for instance) MySQL database dumping. It's in Russian, but the interface is fairly obvious.
You can connect to a server remotely with mysqldump. For example:
mysqldump -u poweruser -h remote.mysql.host database
Maatkit seems quite appropriate for this with mk-parallel-dump and mk-parallel-restore.