I have reached the limit set on the row size of a table, so I'm not able to add any more columns to the table.
I'm getting the following error:
.#1118 - Row size too large. The maximum row size for the used table type, not counting BLOBs, is 65535. You have to change some columns to
TEXT or BLOBs
I have researched this issue on the MySQL website, but am still unsure about how to fix this problem.
Does anyone know how I can fix this issue, and what setting or script that I would need to run to modify the setting so it allows me to add more columns to the table?
Why is your row size 64k to begin with? That is your problem. Not the setting being too low.
From:
http://dev.mysql.com/doc/refman/5.0/en/column-count-limit.html
Each table has an .frm file that contains the table definition. The
server uses the following expression to check some of the table
information stored in the file against an upper limit of 64KB:
> if (info_length+(ulong) create_fields.elements*FCOMP+288+
> n_length+int_length+com_length > 65535L || int_count > 255)
So it's not likely something you can easily change (short of modifying source code and running a custom MySQL. Give us your schema and we might be able to better advise, but the short answer would seem to be that you have too many columns, or need to change some VARCHARs etc. to be text/blob.
Without seeing the (likely abomination of a) schema, it's hard to advise.
Related
I have a table with over 100 columns imported from Access into mysql. the table will be displayed in the typical shared hosting apache environment using PHP and HTML. Almost all fields were coming in as varchar(255). This caused errors of oversize row length on import so i switched many of them to text(0) for import. I would like to make these fields have a size and varchar type so I can index them for search speed. Each of the fields will only contain maybe at most 10 words.
I need to the fields to be set to as small as they can be so I don't push past mysql row maximum.
How do I calculate the size I need for the varchar?
I am a noob at mysql so if I am asking something wrong or lack understanding please explain.
SELECT MAX(LENGTH(field1)) length_field1,
MAX(LENGTH(field2)) length_field2,
-- ..........
MAX(LENGTH(fieldN)) length_fieldN
FROM source_table;
I used to use a query in mySQL that tells me how big my query is.
However, I don't remember that query and can't seem to find it now.
Does anyone know that syntax on top of their head?
Basically it allows me to know how much in size I saved from using a 11 bit integer vs 2 bit integer etc.
Thanks,
Tee
Here's an overview, also with all data types: http://dev.mysql.com/doc/refman/5.1/en/storage-requirements.html
You can use SHOW TABLE STATUS LIKE 'MY_TABLE' to return a bunch of information about the table. The Data_length column will contain the size of the data file used for that table. There is also an "average row length", Avg_row_length, that might be useful.
See here for details: http://dev.mysql.com/doc/refman/5.1/en/show-table-status.html.
As mentioned in my comment above though, the number after an int declaration, int(11), does not affect the size of the data structure that holds the integer. It only affects the display width of the column. Furthermore, you will only see its effect if you are using ZEROFILL.
I was wondering if it is possible to increase the maximum row length of MySQL with InnoDB engine. The current is 8KB.
I would also like to know what enforces this limitation. I do not remember having such a limitation with Oracle 10 or MSSQL 2005.
Thank you!
You have to change the inno_db_page_size, check http://www.mysqlperformanceblog.com/2006/06/04/innodb-page-size/ It can be 8K, 16K, 32K or 64K, 16K is the default.
MS SQL Server has this limitation as well. To get around this, you may use LOBs (like CLOB, BLOB, TEXT, etc) since they are not part of the record itself.
Alternatively you may split your table into two tables linked 1:1. Maybe you could give some background what you try to achieve and why your table is that big.
This is a restriction on InnoDB tables and cannot be changed. According to the docs:
The maximum row length, except for
variable-length columns (VARBINARY,
VARCHAR, BLOB and TEXT), is slightly
less than half of a database page.
That is, the maximum row length is
about 8000 bytes.
You will have to think about redesigning your table.
I just added a new field to my table in mysql and it came back with a warning of "1117: too many columns"
The table has (gasp) 1449 columns. I know, I know it's a ridiculous number of columns and we are in the process of refactoring the schema but I need to extend this architecture just a bit more. That said, this doesn't seem to be reaching the theoretical limit of 3398 as per the mysql documentation. We are also not close to the 64K limit per row as we are in the 50K range right now.
The warning does not prevent me from adding fields to the schema so not sure how it fails if at all. How do I interpret this error given that it does not seem to cause any issues?
Perhaps some of these factors are adding to the total byte count:
http://dev.mysql.com/doc/refman/5.5/en/column-count-limit.html
e.g., if a column allows nulls, that adds to the total or if unicode is used, that more than triples the space required by character columns, etc...
for MyISAM:
row length =
1 +
(sum of column lengths) +
(number of NULL columns + delete_flag + 7)/8 +
(number of variable-length columns)
you could check if it's indeed a row size issue or a column count issue, by adding just a tinyint not null column, then dropping that and adding a char(x) column until you get the error.
If it is a warning as you say, then you should remember that warnings are exactly that: warnings. It means you're okay for now but, if you continue with the behaviour that elicited the warning, you will probably be punished in one form or another.
However, it's more likely that this is an error in that it's refused to actually let you add more columns. Even if it does let you add more columns, that's unlikely to last for long.
So, regardless of whether it's a warning or error, the right response is to listen to what it's telling you, and fix it.
If you need a quick'n'dirty fix while you're thinking about the best way to fix it properly, you can split the row across two tables with a common identifier.
This will make your queries rather ugly but will at least allow you to add more columns to the "table" (quoted because it's actually two tables with a common key).
Don't use this as a final solution, not least of all because it breaks normalisation rules. But, to be honest, with more than a thousand columns, there's a good chance they're already broken :-)
I'm finding it very hard to imagine an item that would have thousands of attributes that couldn't be organised into a better hierarchy.
MySQL specifies the row format of a table as either fixed or dynamic, depending on the column data types. If a table has a variable-length column data type, such as TEXT or VARCHAR, the row format is dynamic; otherwise, it's fixed.
My question is, what's the difference between the two row formats? Is one more efficient than the other?
The difference really only matters for MyISAM, other storage engines do not care about the difference.
EDIT : Many users commented that InnoDB does care: link 1 by steampowered, link 2 by Kaan.
With MyISAM with fixed width rows, there are a few advantages:
No row fragmentation: It is possible with variable width rows to get single rows split into multiple sections across the data file. This can increase disk seeks and slow down operations. It is possible to defrag it with OPTIMIZE TABLE, but this isn't always practical.
Data file pointer size: In MyISAM, there is a concept of a data file pointer which is used when it needs to reference the data file. For example, this is used in indexes when they refer to where the row actually is present. With fixed width sizes, this pointer is based on the row offset in the file (ie. rows are 1, 2, 3 regardless of their size). With variable width, the pointer is based on the byte offset (ie. rows might be 1, 57, 163). The result is that with large tables, the pointer needs to be larger which then adds potentially a lot more overhead to the table.
Easier to fix in the case of corruption. Since every row is the same size, if your MyISAM table gets corrupted it is much easier to repair, so you will only lose data that is actually corrupted. With variable width, in theory it is possible that the variable width pointers get messed up, which can result in hosing data in a bad way.
Now the primary drawback of fixed width is that it wastes more space. For example, you need to use CHAR fields instead of VARCHAR fields, so you end up with extra space taken up.
Normally, you won't have much choice in the format, since it is dictated based on the schema. However, it might be worth if you only have a few varchar's or a single blob/text to try to optimize towards this. For example, consider switching the only varchar into a char, or split the blob into it's own table.
You can read even more about this at:
http://dev.mysql.com/doc/refman/5.0/en/static-format.html
http://dev.mysql.com/doc/refman/5.0/en/dynamic-format.html
One key difference occurs when you update a record. If the row format is fixed, there is no change in the length of the record. In contrast, if the row format is dynamic and the new data causes the record to increase in length, a link is used to point to the "overflow" data (i.e. it's called the overflow pointer).
This fragments the table and generally slows things down. There is a command to defragment (OPTIMIZE TABLE), which somewhat mitigates the issue.
This page in MySQL's documentation seems to contradict the top answer here, in that DYNAMIC row format means something for InnoDB tables as well:
https://dev.mysql.com/doc/refman/5.7/en/innodb-row-format.html
Fixed means that every row is exactly the same size. That means that if the 3rd row on a data page needs to be loaded, it will be at exactly PageHeader+2*RowSize, saving some access time.
In order to find the beginning of a dynamic record, the list of record offsets must be consulted, which involves an extra indirection.
In short, yes, there's a slight performance hit for dynamic rows. No, it's not a very big one. If you think it will be a problem, test for it.
Fixed should be faster and more secure than dynamic, with the drawback of having a fixed char-lenght.
You can find this information here: http://dev.mysql.com/doc/refman/5.0/en/static-format.html