Does mysql have any datarows limit.
I mean there's gotta be a limit somewhere, or maybe just a limit for a user.
Anyone knows if there is a limit for a user?
Yes there is a limit (Actually there are a few).
The file size of your filesystem. Since MySQL (all engines) stores the table in a maximum of 1 file (InnoDB can store multiple tables in one file), the filesystem's file size limit will be restrictive of how many rows you can have. Now, if you're using a modern filesystem, it won't be too bad. See this list for more information: Comparison of filesystem limits.
The row pointer in the storage engine (MyISAM for instance is 6 bytes by default, 7 bytes max). Granted, these numbers are huge (256TB default, 65,536TB max for MyISAM), but they are there.
Data type of your primary key. If you use INT, you're capped at 2.1 billion rows (4.3 if you used unsigned). If you used a BIGINT, you're capped at 9.2x10^18 rows (18.4x10^18 if unsigned). Of course this doesn't apply to tables without an auto-incremeneted PK.
InnoDB's maximum tablespace size is 64TB, so that's the max table size in Inno.
There may be more, but that's what I can think of...
Check out this documentation page for more information...
As far as I know, there is no row limit as such, and there definitely is no per-user limit - it would not make sense in a database system.
See E.7. Limits in MySQL in the manual and the duplicate link I posted.
Related
We have a table partitioned by key (binary(16))
Is there any option to calculate which partition record will go outside of MySQL?
What is the hash function (not linear one)?
The reason is to sort the CSV files outside MySQL and insert them in parallel in right partitions with LOAD DATA INFILE and then index in parallel too.
I can't find the function in MySQL docs
What's wrong with Linear? Are trying to LOAD in parallel?
How many indexes do you have? If only that hash, sort the table, then load into a non-partitioned InnoDB with the PK already in place. Meanwhile, make sure every column uses the smallest possible datatype. How much RAM do you have?
If you are using MyISAM, consider MERGE - With that, you can load each partition-like table as in a separate thread. When finished, construct the "merge" table that combines them.
What types of queries will you be using? Single row lookups by the BINARY(16)? Anything else might have big performance issues.
How much RAM? We need to tune either key_buffer_size or innodb_buffer_pool_size.
Be aware of the limitations. MyISAM defaults to a 7-byte data pointer and a 6-byte index pointer. 15TB would need only a 6-byte data pointer if the rows are DYNAMIC (byte pointer), or 5 bytes if they are FIXED (row number). So that could be 1 or 2 bytes to be saved. If anything is variable length, go with Dynamic; it would waste too much space (and probably not improve speed) to go fixed. I don't know of the index pointer can be shrunk in your case.
You are in 5.7? MySQL; 8.0 removes MyISAM. Meanwhile, MariaDB still handles MyISAM.
Will you first split the data by "partition"? Or send off INSERTs to different "partitions" one by one. (This choice adds some more wrinkles and possibly optimizations.)
Maybe...
Sort the incoming data by the binary version of MD5().
Split into chunks based on the first 4 bits. (Or do the split without sorting first) Be sure to run LOAD DATA for one 4-bit value in only one thread.
Have PARTITION BY RANGE with 16 partitions:
VALUES LESS THAN 0x1000000000000000
VALUES LESS THAN 0x2000000000000000
...
VALUES LESS THAN 0xF000000000000000
VALUES LESS THAN MAXVALUE
I don't know of a limit on the number of rows in a LOAD DATA, but I would worry about ACID locks having problems if you go over, say, 10K rows at a time.
This technique may even work for a non-partitioned table.
I currently have a table with 10 million rows and need to increase the performance drastically.
I have thought about dividing this 1 table into 20 smaller tables of 500k but I could not get an increase in performance.
I have created 4 indexes for 4 columns and converted all the columns to INT's and I have another column that is a bit.
my basic query is select primary from from mytable where column1 = int and bitcolumn = b'1', this still is very slow, is there anything I can do to increase the performance?
Server Spec
32GB Memory, 2TB storage, and using the standard ini file, also my processor is AMD Phenom II X6 1090T
In addition to giving the mysql server more memory to play with, remove unnecessary indexes and make sure you have index on column1 (in your case). Add a limit clause to the sql if possible.
Download this (on your server):
MySQLTuner.pl
Install it, run it and see what it says - even better paste the output here.
There is not enough information to reliably diagnose the issue, but you state that you're using "the default" my.cnf / my.ini file on a system with 32G of memory.
From the MySQL Documentation the following pre-configured files are shipped:
Small: System has <64MB memory, and MySQL is not used often.
Medium: System has at least 64MB memory
Large: System has at least 512MB memory and the server will run mainly MySQL.
Huge: System has at least 1GB memory and the server will run mainly MySQL.
Heavy: System has at least 4GB memory and the server will run mainly MySQL.
Best case, you're using a configuration file that utilizes 1/8th of the memory on your system (if you are using the "Heavy" file, which as far as I recall is not the default one. I think the default one is Medium or perhaps Large).
I suggest editing your my.cnf file appropriately.
There several areas of MySQL for which the memory allocation can be tweaked to maximize performance for your particular case. You can post your my.cnf / my.ini file here for more specific advice. You can also use MySQL Tuner to get some automated advice.
I made something that make a big difference in the query time
but it is may not useful for all cases, just in my case
I have a huge table (about 2,350,000 records), but I can expect the exact place that I should play with
so I added this condition WHERE id > '2300000' as I said this is my case, but it may help others
so the full query will be:
SELECT primary from mytable where id > '2300000' AND column1 = int AND bitcolumn = b'1'
The query time was 2~3 seconds and not it is less than 0.01
First of all, your query
select primary from from mytable where column1 = int and bitcolumn = b'1'
has some errors, like two from clauses. Second thing, splitting the table and using an unnecessary index never helps in performance. Some tips to follow are:
1) Use a composite index if you repeatedly query some columns together. But precautions must be taken, because in a composite index the order of placing a column in the index matters a lot.
2) The primary key is more helpful if it's on int column.
3) Read some articles on indices and optimization, they are so many, search on Google.
I am running a query that creates a temporary table however the limit is 64mb and I am not able to change the limit due to access permissions etc. When a large date range is selected the temporary table runs out of space and results in a mysql error.
Is there anyway I can determine the size or amount of memory the query will use before attempting to run the query, so I can avoid the above problem gracefully?
There's no way to limit the size of the temp table directly, except by querying for a smaller number of rows in your base SQL query.
Can you be more specific about the error you're seeing? MySQL temporary tables can exist in memory up to the lesser of tmp_table_size and max_heap_table_size. If the temp table is larger, MySQL converts it to an on-disk temp table.
This will make the temp table a lot slower than in-memory storage, but it shouldn't result in an error unless you have no space available in your temp directory.
There's also a lot of ways MySQL uses memory besides temp table storage. You can tune variables for many of these, but it's not the same as placing a limit on the memory a query uses.
The error 1114 indicates that you've run out of space. If it were an InnoDB table on disk, this probably means you have an ibdata1 file without autoextend defined for the tablespace. For a memory table, it means you're hitting the limit of max_heap_table_size.
Since you can't change max_heap_table_size, your options are to reduce the number of rows you put into the table at a time, or else use an on-disk temp table instead of in memory.
Also be careful about using the most current release of the major version of MySQL. I found bug 18160 that reports MySQL calculating table size incorrectly for heap tables (which are used for in-memory temp tables). So for example make certain you're using at least MySQL 5.0.23 or 5.1.10 to get the fix for that bug.
I'm not aware of a direct way to accomplish this, but you could use the information about the used tables provided by SHOW TABLE STATUS like for example the average row size and then calculate the number of records returned by your query using SELECT COUNT(*) .... If you need to be really save calculate the maximum size of a row by using the columns types.
Maybe it would be easier to check the number of records which can be handled and then either specify a fixed LIMIT clause or to react on SELECT COUNT(*) ....
How many records can a MySQL MyISAM table store? How many InnoDB can?
You can't count by number of records because your table can have really short records with only a few int fields or your records might be really long with hundreds of fields.
So it has to be measured in the file size of the tables.
For MYSQL: The table size limit is based on the operating system drive file system that MySQL is installed on, ranging from 2GB to 2TB.
See the MySQL reference manual for full explanations of limits for each operating system.
Concerning InnoDb and MyIsam i do not know.
From the MySQL site:
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.
The more practical limit will be the size of your key -- if your primary key is an int field, then the max number of rows will be the largest number that can be held in an int.
So if you're expecting a big table size, use bigint ... or something even bigger.
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.