Is there any limit to maximum row of table in DBMS (specially MySQL)?
I want create table for saving logfile and it's row increase so fast I want know what shoud I do to prevent any problem.
I don't think there is an official limit, it will depend on maximum index sizes and filesystem restrictions.
From mySQL 5.0 Features:
Support for large databases. We use MySQL Server with databases that contain 50 million records. We also know of users who use MySQL Server with 200,000 tables and about 5,000,000,000 rows.
You should periodically move log rows out to a historical database for data mining and purge them from the transactional database. It's a common practice.
There's probably some sort of limitation, dependent on the engine used and the table structure. I've got a table with appx 45 million entries in a database I administrate, I've heard of (much) higher numbers.
Related
Is it OK to keep 10000+ tables in a MySQL database?
I'm making a messaging/chat script, so I'm thinking about partitioning data's over several tables as it will be a huge amount of data after some days.
IS IT OK?
Or it has some effect?
Well, as a table can hold millions of rows so I was thinking maybe a database can hold large number of tables too
or, the question could be like, how does Facebook stores their huge amount of daily chat messages?
I'm a newbie in MySQL, please help
MySQL has no limit on the number of tables. The underlying file system may have a limit on the number of files that represent tables. Individual storage engines may impose engine-specific constraints. InnoDB permits up to 4 billion tables.
Even so, the typical DBMS will 'handle' such large databases, but there is more strain on the system catalog than usual in such systems.
I have about huge tables in one database with no ill effects, other than displaying the table list in phpMyAdmin taking a while
It's possible, but I would avoid it unless you have a really good use case for it. It raises all kinds of scalability and maintainability issues. Your table size is mainly limited by available disk space.
If you really need to do it...
You'll need to increase the maximum number of file descriptors that your OS will allow to have open, since MyISAM tables use two file descriptors per table. (If you're using Linux then read the section about ulimit in the man page for bash for how to do this).
Also, there's a MySQL config value called table_cache that limits the number of allowed tables. You'll need to make sure that's large enough to support the number of tables you need.
You won't want to use the standard "flush tables" anymore (unless you're the kind of person that likes to watch paint dry) so you'll need to flush each table individually (e.g. before shutdown).
Again, I would avoid using so many tables. You're probably better off making your schema support what you need in a handful of tables, and consider archiving, warehousing (or deleting!) old data if you're concerned about storing too much data.
Our server (several Java applications on Debian) handles incoming data (GNSS observations) that should be:
immediately (delay <200ms) delivered to other applications,
stored for further use.
Sometimes (several times a day maybe) about million of archived records will be fetched from the database. Record size is about 12 double precision fields + timestamp and some ids. There are no UPDATEs; DELETEs are very rare but massive. Incoming flow is up to hundred records per second. So I had to choose storage engine for this data.
I tried using MySQL (InnoDB). One application inserts, others constantly check last record id and if it is updated, fetch new records. This part works fine. But I've met following issues:
Records are quite large (about 200-240 bytes per record).
Fetching million of archived records is unacceptable slow (tens of minutes or more).
File-based storage will work just fine (since there are no inserts in the middle of DB and selections are mostly like 'WHERE ID=1 AND TIME BETWEEN 2000 AND 3000', but there are other problems:
Looking for new data might be not so easy.
Other data like logs and configs are stored in same database and I prefer to have one database for everything.
Can you advice some suitable database engine (SQL preferred, but not necessary)? Maybe it is possible to fine-tune MySQL to reduce record size and fetch time for continious strips of data?
MongoDB is not acceptable since DB size is limited on 32-bit machines. Any engine that does not provide quick access for recently inserted data is not acceptable too.
I'd recommend using TokuDB storage engine for MySQL. It's free for up to 50GB of user data, and it's pricing model isn't terrible, making it a great choice for storing large amounts of data.
It's got higher insert speed compared to InnoDB and MyISAM and scales much better as the dataset grows (InnoDB tends to deteriorate once working dataset doesn't fit the RAM making its performance dependant on the I/O of the HDD subsystem).
It's also ACID compliant and supports multiple clustered indexes (which would be a great choice for massive DELETEs you're planning to do). Also, hot schema changes are supported (ALTER TABLE doesn't lock the tables, and changes are quick on huge tables - I'm talking gigabyte-sized tables being altered in mere seconds).
From my personal use, I experienced about 5 - 10 times less disk usage due to TokuDB's compression, and it's much, much faster than MyISAM or InnoDB.
Even though it sounds like I'm trying to advertise this product - I'm not, it's just simply amazing since you can use monolithic data-store without expensive scaling plans like partitioning across nodes to scale the writes.
There really is no getting around how long it takes to load millions of records from disk. Your 32-bit requirement means you are limited in how much RAM you can use for memory based data structures. But, if you want to use MySQL, you may be able to get good performance using multiple table types.
If you need really fast non-blocking inserts. You can use the black hole table type and replication. The server where the inserts occur has a black hole table type that replicates to another server where the table is Innodb or MyISAM.
Since you don't do UPDATEs, I think MyISAM would be better than Innodb in this scenario. You can use the MERGE table type for MyISAM (not available for Innodb). Not sure what your data set is like, but you could have 1 table per day (hour, week?), your MERGE table would then be a superset of those tables. Assuming you want to delete old data by day, just redeclare the MERGE table to not include the old tables. This action is instantaneous. Dropping old tables is also extremely fast.
To check for new data, you can look at "todays" table directly rather than going through the MERGE table.
Is it bad to have too many tables in a database? I have about 160 tables in one database. Is it better to split it into several database rather than using a single database? Single database is more convenient for me.
There are no server limits on the number of tables in a MySQL database. You will definitely have no problems with 160 tables, and you don't need to split them into multiple databases.
You will not gain performance by splitting your tables into multiple databases. If performance remains an issue, you could consider using per-table tablespaces in order to place some sets of tables on different physical disks.
according to MySQL reference manual:
MySQL has no limit on the number of tables. The underlying file system may have a limit on the number of files that represent tables. Individual storage engines may impose engine-specific constraints. InnoDB permits up to 4 billion tables.
160 tables isn't radically huge.
16,000 might be...probably would be...more unreasonable - such databases exist in ERP or CRM systems (even into the 40-50K tables range, but many of those tables are not actually used, or are only barely used).
Even so, the typical DBMS will 'handle' such large databases, but there is more strain on the system catalog than usual in such systems.
160 is still ok. it makes SQL command more faster than making too many contents under a single table. In my case I have 8,545,214 tables in a single Mysql database. I dont want to store millions of user in a single database that's why I used multiple table to store each post a user done. it makes mysql more faster than searching on a single table with millions of rows.
WordPress Multisite creates dozens of tables for every new subsite in the same database.
So you can be so good at only 160 tables.
It might be an issue to manage them with PhpMyAdmin or other software to see and scroll through the tables. But if you work with the code it should not be a problem.
I have a MySQL database that contains millions of rows per table and there are 9 tables in total. The database is fully populated, and all I am doing is reads i.e., there are no INSERTs or UPDATEs. Data is stored in MyISAM tables.
Given this scenario, which linux file system would work best? Currently, I have xfs. But, I read somewhere that xfs has horrible read performance. Is that true? Should I shift the database to an ext3 file system?
Thanks
What about a RAM disk?
it's not about the FS but it can improve your SELECTs. did you evaluated the mysql table partitioning ?
I've a database with 3 of the tables having rows in excess of 20 million each. I've used GUIDs as primary keys (unfortunately). Now our database is about 20GB and growing 5GB per month.
It takes about 2 hrs to take full backup of the database, and 30hrs to restore on a box with 4GB RAM.
We once have all the tables from database disappeared. other mysql databases in same server were alright except one - for which only data was disappeared leaving empty tables.
A select query (among many slow queries) - which get max of a date column in one of 20m table takes about 5 mins to return result. This query used pretty frequently.
What I'm looking answers for
recommended db design changes
ways to improved select query performance - max date column on 20m records
other queries' performance
how to go about handling future db growth
Thanks all for your attention.
I've seen setups of larger size (with InnoDB as storage engine and a GUID as a primary key), and there were no such problems.
We once have all the tables from database disappeared. other mysql databases in same server were alright except one - for which only data was disappeared leaving empty tables.
The tables may seem empty if the system LSN has gone below the each page's LSN. This may happen if the InnoDB logfiles are corrupt. InnoDB, however, will issue a warning in this case.
A select query (among many slow queries) - which get max of a date column in one of 20m table takes about 5 mins to return result. This query used pretty frequently.
Create an index on this column, the query will be instant.
Please post the exact query and I'll tell you how to create the best index.
I see no problem in the DB design as such, most probably it's something with your server.
Is it possible to reproduce this behavior on another server with a clean vanilla MySQL installation?
You may also want to try to split data between the tables. Set innodb_file_per_table and restore from the backup.
A free alternaive to innodb hot backup is Percona XtraBackup Tool.
For backup, you could use the innodb hot backup tool. This not only lets you do consistent backups while your database is up, but the restore is much faster than the one you're doing (I'm assuming mysqldump?). It does cost money.
You might also try Mydumper: http://www.mydumper.org/
It is a great tool and is free and open source