I have a mysql database, and today I woke up and noticed that some of my tables are empty (like if they were truncated) but some aren't. This is not an SQL injection since I took care of that, but still haven't figured out what really happened.
Now I need to recover that data that was deleted, but the only thing I have are the lib files, so, is there a way to recover a database data using those files? We never deleted any file.
Basically I have ib_logfile, ibdata files but I never enabled Binary Logging.
Related
I'm trying to create a DataBase for a very little program that just I and 2 more friends use, so the database will be little.
What I want to do is to share this database with these 2 friends, so I thought about storing the data in a OneDrive shared folder.
At the moment, I'm using a txt file as a "database". Which is placed in a shared OneDrive folder, so when my friends execute the program, it can read the data from there and make it sort of real time "online".
The thing is that I can't find the my.ini file in my
C:\Program Files\MySQL\MySQL Server 8.0\
directory, so I can't change the data folder.
Another trouble I have is that I also don't have the Data folder in that directory, instead I've found it in this one:
C:\Program Files\MySQL\MySQL Workbench 8.0 CE
Is it possible to do what I want to do? And how should I proceed?
Do you think I should be using MySQL 5.x version?
Thanks
If you want to share a database with a couple of other users, putting the datadir in OneDrive isn't going to work.
MySQL stores data in the files under the datadir, that's true. They're stored in files called tablespaces which have the .ibd extension.
But as you do INSERT/UPDATE/DELETE operations, data is temporarily stored in memory and in the transaction logs (ib_logfile*. MySQL has to do a delicate coordination between these, to save data in a durable way, while ensuring good performance. It works well, but only if the MySQL Server is the only process writing to the files.
OneDrive is not coordinating with MySQL at all. It will periodically check for files that have changed since it last did a sync. The interval OneDrive checks files is about every 10 minutes, and this is not configurable.
OneDrive may choose to sync the files at a moment after you've done some INSERT/UPDATE/DELETE operations, and the data is modified in RAM, but hasn't yet been updated in the tablespace files on disk.
Once you've committed a change, it must also be safely stored in the transaction log, even if it isn't updated in the tablespace. But if your friends receive the files in this state (transaction log contains changes which aren't present in the tablespace), they can reconstruct the data from your RAM that they didn't get. This is called InnoDB crash recovery. MySQL Server does if automatically if it starts up and finds the transaction log contains changes that aren't in the tablespace. It assumes you had a sudden reboot and lost what was in RAM.
If your friends try to just keep their MySQL Server running continuously, reading a datadir that is simultaneously being updated by their one OneDrive, it'll basically overwrite their files and MySQL will become confused. It only checks to see if it should do crash recovery as MySQL Server starts. So if the files change in unexpected ways while MySQL Server is already running, it'll just conclude that your hard drive has gotten corrupted. It'll probably report a fatal error and shut down MySQL.
Also if your friends try to make changes of their own to the database, their changes would conflict with the updates from OneDrive. Then their attempts to overwrite files would eventually be synchronized in the opposite direction via OneDrive, and would eventually corrupt your database too. This would happen without warning at 10 minute intervals, whenever OneDrive chose to do its file sync.
So I'm afraid OneDrive is not the solution to share your database.
Alternatives that do have a chance of working include:
Hosting a single instance of MySQL Server on a website that you all share, and giving each of you a client that can use the database. A popular free client is phpMyAdmin. That way there'd be only one instance of MySQL Server, one datadir, even though you each would be concurrent clients reading and writing data. This is the simplest solution, most likely to work.
Exporting the data from your MySQL Server instance using mysqldump periodically, and putting the export file on OneDrive, or sending it to your friends through email or any other means. Then they would have to import that data to their MySQL Server manually. This would overwrite any changes they had done to their database, but it wouldn't appear as corruption. If they want to send changes back to you, they could do a similar operation: export their database, put the dump file on OneDrive, then you'd get their dump file and import it to your MySQL Server instance, overwriting any changes you had done locally since the last time you sent your export to your friends.
Use a MySQL add-on for multi-server synchronous replication, such as InnoDB Group Replication or Percona XtraDB Cluster. But this is probably too complex for you to set up if you're a newbie with MySQL.
I am attempting to restore my old databases to a new Wamp installation. However, I did not take a backup of Mysql files before I did this. Thankfully the uninstallation has not deleted all the files, but in my data folder I have :
1) All the databases (As folders)
2) auto.cnf
There are no ib* files in the old folder. Is it still possible to restore my databases somehow?
I have tried to replace the entire mysql5.6.17 folder (there has been no change of version between the installations), but Wamp remains orange and never turns green.
If I replace only the data folder, the MySQL service starts, I can see the databases, but not the tables.
If I change the path in my.ini to point to the old wamp's data folder, I cannot see the old databases at all.
EDIT : Was experimenting a bit, copying the database folders directly into the new Wamp's data folder allows me to get a list of all the tables properly, but there is no actual data in the tables, and trying to query it using MySQLWorkbench gives me the error :
Error Code: 1146. Table 'testdb.users' doesn't exist
EDIT 2 : Found this in the error log file in my data folder :
2014-08-03 06:24:46 25164 [Warning] InnoDB: Cannot open table testdb/users from the internal data dictionary of InnoDB though the .frm file for the table exists. See http://dev.mysql.com/doc/refman/5.6/en/innodb-troubleshooting.html for how you can resolve the problem.
As I thought, its a problem with InnoDB's own mapping. Is there a way to resolve this manually?
If you created an INNODB database, and made no other config changes to store the actual data in seperate table spaces then all the actual data for that INNODB databases will have been stored in the \wamp\bin\mysql\mysql5.6.17\ibdata1 file.
If you do not have that file from the old install then your data is lost.
There will also be info in a \wamp\bin\mysql\mysql5.6.17\data\DATA_BASE_NAME\ folder, one .frm file for each table that was in the database, but this is basically just schema information and not actual data.
For future reference, InnoDB Backup and Recovery
GOLDEN RULE:
Always backup database (from phpmyadmin) before major changes.. better to spend 1 minute for that, than going into trouble..
How to Copy data folder
If you want to copy the database, then INSTALLATION/mysql versions should be same.. then rename newly installed data folder to i.e. data_my_old,so now there you can place the backuped data folder (it should contain ibdata1 file).
Depends on innodb_file_per_table setting.
If it was OFF then all your tables were in ibdata1. Now you have quite new ibdata1 (since you see errors "Cannot open table testdb/users from the internal data dictionary", that means InnoDB runs fresh new dictionary). That means that now the data is somewhere on the disk. The recovery is quite difficult and requires a lot of tedious work. You need to take an image of the disk, scan it with stream_parser to find InnoDB pages, then recover the InnoDB dictionary, then find index_id of every table and if the stream_parser has found this index run c_parser to extract records from the index.
If innodb_file_per_table was ON and you do see .ibd files in the databases directories then recovery is much easier. First, you may try to reconnect individual ibd files with ibdconnect or extract records from the ibd files with stream_parser/c_parser.
The mentioned tools are part of TwinDB data recovery toolkit
i have just done a google search and found this....
Go to C:\wamp\bin\mysql\mysql5.5.24\data
Find a file called "mysql-bin.index"
Rename that file to "mysql-bin.index-corrupt"
Restart the server and it will work fine, all your database will be where you left them.
I want to purge the ibdata1, ib_logfile0 and ib_logfile1 files in MySQL. Because these files are taking too much space of my C:\ disk. And I don't want to move these files anywhere else in the Hard disk. I heard about purging which can shrink the data. I am using Windows Vista. What are the steps to be done to purge the data ?
The log files can be removed anytime. Only the most recent log is kept open/locked. However, deleting id_data will trash all of your InnoDB databases - that's the actual data store.
As pointed out by MarcB, you can delete the (old) logfiles without problems; MySQL does not need them to run.
The data file ibdata* must not be deleted, it contains the actual database data.
I will grow as the database grows; unfortunately there is not way to shrink it, even if you later delete data from the database. The only way is to dump and reimport the whole database.
Also see this question: MySQL data file won't shrink
It explains various options to better cope with growing data files.
Short answer: There's no way to reduce the size of the ibdata files once they grew to a certain size. MySQL recommends dumping all innodb type data, shutting down mysql, deleting the ibdata files and restarting, then loading the data again. A one-click "compact" solution like other systems have is still missing.
I am having to restore a mysql database from .myd and .frm files. And Ii have no idea where to begin, I tried just copying them over while preserving file permisssions but to no avail what other steps do i need to take?
I have a feeling its got something to do with the ib_logfile0, ib_logfile1 and ib_data files. But dont know what to do.
You shouldn't be doing backups by dealing with the raw MySQL files. It's trivially easy to end up with a corrupted database that way. Consider what happens when you start copying the files to your backup medium - the copy will take a non-zero amount of time, during which the database could potentially write new data in various places, including the parts you've already copied. Now you're copying a modified file, a mix of old data and new data. This modified copy is almost guaranteed to be corrupted.
You should be using mysqldump or mysqlhotcopy instead, which guarantee a consistent backup.
However, on the chance that your database is relatively quiet and you managed to get a good clean backup copy, the files you need to restore depend on the type of tables you're restoring. InnoDB stores all of its data in the ib* files, regardless of database/table name. MyISAM uses files in directories named according to the database/table names.
After copying the backup copies into the correct locations, you'll have to restart MySQL, as it will still be accessing the original copies of the files.
The short question:
Is it safe skip ib_logfile* files while creating custom-made backup of MySQL installation with InnoDB engine used?
Custom-made backup is just copy all (or subset of) /var/lib/mysql + /etc/my.cnf to safe place.
As I know ib_logfile* files are recreated by MySQL on start + the files are really huge, so that may not be wise to store them in backup. And yes, assume MySQL is (correctly) stopped before backup.
It's not safe to back up a database in the manner you're describing.
The reason is that you cannot know if some data pages are still in MySQL Server's memory, pending an I/O flush to disk. So copying the files has a good chance of copying garbage, whether or not you include the ib_log files.
Don't do what you're doing. Use mysqlbackup or InnoDB's Hot Backup product.
edit:
Read Farhan Mashraqi's blog article about InnoDB Performance Optimization, in which he says you can delete the ib_log files if you have shut down MySQL Server.
InnoDB log resizing: is not as simple
as changing option and restarting. You
need to shut down MySQL server and
make sure it shuts down normally
(check error log for errors to
confirm). Then move away InnoDB log
files ib_log*. Then start the MySQL
server and check error log files to
see if it successfully created new log
files.
So yes, you should be able to do a filesystem copy of the ibdata files only. You don't need to include the ib_log files, because they should be recreated as MySQL Server starts up. I reiterate, however, that I do not recommend backing up databases with filesystem copy.
Suppose you back up a database today in this manner, using MySQL 5.0. Someday later you need to restore the backup, but by that time you'll be using some future version like MySQL 6.5 for example. Do the ib_data files still use the same internal format in that future version? Will MySQL 6.5 read those files you backed up today? You can't be sure. The backup format is intended to be more portable.