When I try to modify size of varchar:
alter table foo modify column content varchar(20000);
I got this error:
ERROR 1118 (42000): Row size too large. The maximum row size for the used table type,
not counting BLOBs, is 65535. This includes storage overhead, check the manual.
You have to change some columns to TEXT or BLOBs
How to use varchar with large data ?
Youssef, I think you're getting confused between varchar size and row size. A varchar can be up to 65533 in length (2 bytes are reserved to define the length) so your varchar is within the accepted size, however the other columns in your table must add up to more than 45535 bytes - thus giving you a "row" size error.
If you post your existing create table script we can confirm that this is the case.
The pertinent section in the manual is C.10.4 Limits on Table Column Count and Row Size
Related
I have fixed length data in MYSQL Database.
So my question is that which data type among the VARCHAR and CHAR is more suitable to be used with respect to performance, Space, Time and speed?
since you have data is of fixed length you should use the CHAR.
For example:
The following statement creates a table with a CHAR column having the fixed length. i.e. CHAR(3) fixed length is 3.
CREATE TABLE mysql_char_test (
status CHAR(3)
);
When defining a column in SQL Server we can do [Photo] VARBINARY(MAX), this automatically sets the length of the field to the maximum. In MySQL I've tried to do the same but it seems that that this should be done in another way. So, I've been looking for the equivalent of this in MySQL. I've tried googling by I keep coming up with the results defining the max in numeric value like 65535. Tried that, but the MySQL says it is too large for the field.
No in MySQL there's no such a const MAX which defines the maximum column length. Values in VARCHAR columns are variable-length strings. The length can be specified as a value from 0 to 65,535. The effective maximum length of a VARCHAR is subject to the maximum row size (65,535 bytes, which is shared among all columns) and the character set used.
The equivalent to varbinary(max) would LONGBLOB in MySQL:
http://dev.mysql.com/doc/refman/5.5/en/blob.html
I'm trying to update a row in a table but it comes back with:
Row size too large. The maximum row size for the used table type, not counting BLOBs, is 8126. You have to change some columns to TEXT or BLOBs
All of my fields apart from the ID are BLOBs so I have no idea what the error is meaning.
Can anybody help?
Just change your columns type to TEXT as mysql said.
I have 22 database fields of type longtext. If I try saving 12 of the fields with the following data I get the following error:
#1118 - Row size too large. The maximum row size for the used table type, not
counting BLOBs, is 8126. You have to change some columns to TEXT or BLOBs
It saves fine if I only save 11 fields. Here's the data:
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
How can I fix the issue? How can I increase the bytes of the row size so it is more than 8126?
The problem is the row size limit for InnoDB tables, in this links you can find some approaches to solve this:
http://www.mysqlperformanceblog.com/2011/04/07/innodb-row-size-limitation/
https://dba.stackexchange.com/questions/6598/innodb-create-table-error-row-size-too-large
Columns of type Varchar's, text, and blob arent included in the innodb row size limit.. so if you have a lot of columns that aren't you can get that error.
I had a load of char(1)'s that I changed to varchar and it fixed the problem nicely
Regarding innodb, someone recently told me:
"the varchar content beyond 768 bytes
is stored in supplemental 16K pages"
This is very interesting. If each varchar will be latin1, which I believe stores as 1byte per letter, would a single varchar(500) (<768 bytes) require an extra i/o as a varchar(1000) (>768 bytes) would??
(this question is to find out if all varchars or just big varchars are split into a separate page)
Is the 768 limit per varchar or for all varchars in the row added together? (for example, does this get optimized - varchar(300), varchar(300), varchar(300): [where each individual varchar column is below 768 but together they are above 768 characters]?
I am confused about if the 768 limit relates to each individual varchar or all varchars in the row totaled (as in the question). Any clarification?
EDIT: Removed part about CHARS due to finding out about their limit of 255 max.
The documentation of the current MySQL does not mention this constraint. It actually gives the impression that VARCHAR is stored in the row itself, as the sum of the length of all VARCHARs together in a row cannot be more than 65k bytes.
It also mentions that storage is length+data, which is different from what you describe.
I did find a mention of a splitted storage in MySQL compression internals:
Tables created in previous versions of
InnoDB use the “Antelope” file format,
which supports only
ROW_FORMAT=REDUNDANT and
ROW_FORMAT=COMPACT. In these formats,
InnoDB stores the first 768 bytes of
BLOB, VARCHAR and TEXT columns in the
clustered index record along with the
primary key. The 768-byte prefix is
followed by a 20-byte pointer to the
overflow pages that contain the rest
of the column value.
To me this suggests that each column is considered individually when determining whether that column needs an overflow.
This seems to contrast with newer versions of MySQL which seem to store VARCHAR quite differently. A VARCHAR in a newer version has a max length of 65k bytes, which seems to be stored in the record iself (no overflow), which results in the constraint that all columns together may not be longer than 65k byte.
a CHAR is very different. It's maximum length is 255, and it is stored in the row itself. So no CHAR(500) :)
The length of a CHAR column is fixed
to the length that you declare when
you create the table. The length can
be any value from 0 to 255. When CHAR
values are stored, they are
right-padded with spaces to the
specified length. When CHAR values are
retrieved, trailing spaces are removed
unless the PAD_CHAR_TO_FULL_LENGTH SQL
mode is enabled.