In mysql there is a hard limit of row size of 65,535 bytes which I believe is based of page size. Is there a similar restriction with Sqlite3?
I tried reading through https://www.sqlite.org/limits.html on the Sqlite site but found no specific indication there is. But then I am not a DB expert so maybe I missed something.
The limits page you link to says this:
During part of SQLite's INSERT and SELECT processing, the complete content of each row in the database is encoded as a single BLOB. So the SQLITE_MAX_LENGTH parameter also determines the maximum number of bytes in a row.
(emphasis mine)
So SQLITE_MAX_LENGTH is the maximum length of a row, including any BLOB values.
The default is 1000000000 bytes.
For what it's worth, the row length limit in MySQL of 65535 bytes does not apply to BLOB/TEXT columns. And it has nothing to do with page size.
Related
Issue is to create index for table 'visits_visit' (Django visit app), because every query lasts at least 60 ms and is going to be worse.
CREATE INDEX resource ON visits_visit (object_app(200), object_model(200), object_id(200));
It returns:
ERROR 1071 (42000): Specified key was too long; max key length is 1000 bytes
What to do? Structure of table is on the screenshot.
See the reference to a possible duplicate question already answered in comments under your question. Or should I say a canonical duplicate target to close this question to if it does close. That said, not much there in that reference in terms of storage engines or character sets.
In your case the character set factors in with the use of string-type columns in your composite index.
A side note is certainly performance. Don't expect a great one in general with what you are attempting. Your index is way too wide and may very well not even be of the intended use. Indexes and their benefit need careful scrutiny. This can be ascertained with the use of mysql explain. See the following, in particular the General Comments section.
Please see the following article Using Innodb_large_prefix to Avoid ERROR 1071 and below is an excerpt.
The character limit depends on the character set you use. For example
if you use latin1 then the largest column you can index is
varchar(767), but if you use utf8 then the limit is varchar(255).
There is also a separate 3072 byte limit per index. The 767 byte limit
is per column, so you can include multiple columns (each 767 bytes or
smaller) up to 3072 total bytes per index, but no column longer than
767 bytes. (MyISAM is a little different. It has a 1000 byte index
length limit, but no separate column length limit within that). One
workaround for these limits is to only index a prefix of the longer
columns, but what if you want to index more than 767 bytes of a column
in InnoDB? In that case you should consider using innodb_large_prefix,
which was introduced in MySQL 5.5.14 and allows you to include columns
up to 3072 bytes long in InnoDB indexes. It does not affect the index
limit, which is still 3072 bytes.
Also see the Min and Max section from the Mysql Manual Page Limits on InnoDB Tables
The 'right' answer is to shorten the fields and/or normalize them.
Do you really have 200-character-long apps, models, etc? If not, shorten the fields.
Probably model is repeated in the table a lot? If so, normalize it and replace the column with the id from normalizing it.
You seem to be using MyISAM; you could (should) also switch to InnoDB. That will change the error message, or it might make it go away.
Are you using utf8 characters? Are you doing everything in English? Changing the CHARACTER SET could make 200 characters mean 200 bytes, not 600 (utf8) or 800 (utf8mb4).
Changing the character set for ip_address would shrink its footprint from 15 * (bytes/char). So would changing from CHAR to VARCHAR. Note also that 15 is insufficient to handle IPv6.
What is the MySQL VARCHAR max size?
I have searched on stackoverflow about varchar vs text and studied the documentation.
Iam not sure if i understood it the right way but let me ask you this. I have got Mysql version 5.5.34 and yes the maximum varchar size is 65535 bytes and the text content on my website cannot exceed more than 600 characters, I would prefer using varchar(600) rather than Text.
Since varchar is stored inline with table and faster and when I read all the answers of the question.
rajukoyilandy answer
varchar has 64K row limit
paxdiablo answer
if your row size is approaching 64K, you may want to examine the schema of your database. It's a rare table that needs to be that wide in a properly set up (3NF) database - it's possible, just not very common.
If you want to use more than that, you can use the BLOB or TEXT types. These do not count against the 64K limit of the row
So I have decided to use Text
http://dev.mysql.com/doc/refman/5.0/en/column-count-limit.html
When I have seen this documentation on the very top it says
Every table (regardless of storage engine) has maximum row size of 65,535 bytes.
Storage engines may place additional constraints on this limit,
reducing the effective maximum row size
My question is, So no matter what you use Text or Varchar, the row limit is 65kb? or if you use Text there is no row limit? Any help is greatly appreciated.
http://dev.mysql.com/doc/refman/5.0/en/column-count-limit.html
BLOB and TEXT columns count from one to four plus eight bytes each
toward the row-size limit because their contents are stored separately
from the rest of the row.
So yes no matter what you use the row limit is 65KB, but since BLOB and TEXT types are stored separately the length of the contents do not count towards the row size, just the initial one to four plus eight bytes do.
This is why you can use LONGBLOB LONGTEXT to store huge files and still be able to have more than just a single LONGBLOB/LONGTEXT column in a table.
As for which is better VARCHAR(600) vs TEXT, with VARCHAR you would be taking up 1802 bytes per column so you still have lots of room to work with when it comes to the row limit. But for performance you would have to do benchmarks as this comment points out inline storage is faster if it frequently used in your queries.
The row size limit applies to the amount of space required to store the row itself, which is not the same as the amount of space required to store the data in the row. From the page you linked to:
BLOB and TEXT columns count from one to four plus eight bytes each toward the row-size limit because their contents are stored separately from the rest of the row.
This is why you can store huge amounts of data in a BLOB or TEXT field without exceeding the row-size limit.
I am updating a row in MySQL which currently has 15 varchar(2500) columns plus a few other small sized columns. I need to allow the user to enter more data in these columns, would it be better to convert them to BLOBS? Is there a maximum recommended number of BLOBS per row?
What is best practice with regards to not exceeding the maximum number of bytes per row whilst still allowing the user flexibility with regards to how much they enter in each column?
Many thanks.
No, there's no maximum recommended number of BLOBS on a row. You are really only limited by the maximum size of the row. There is some performance overhead for accessing each BLOB (the row contains a pointer to the BLOB data which is stored elsewhere, vs. accessing a column value actually stored within the row.)
The best practice is to include the most frequently accessed columns within the row, and limit the size of variable length columns to practical limits. Consider TEXT and/or BLOB columns when the size of the column exceeds the maximum allowed by other datatypes, or when the length of the row exceeds the maximum allowed. Alternatively, consider separate child table(s) for less frequently accessed "long-ish" columns.
I don't want to use TEXT if possible because of the extra overhead. Is it ok to have a VARCHAR(900) or some other high number in the ()?
If you are sure you won't exceed the limits for your column in future its fine.
http://dev.mysql.com/doc/refman/5.6/en/char.html
You row however shouldn't exceed the maximum row size fo 65535 bytes. This limit applies to all your columns in that table.
A TEXT or BLOB columns are just pointed to on disk by an address in the row. Therefore the table can't be stored in memory.
This would mean that every time you select that column you will have to access the file system which will be slower. A recommendation that i have often seen is to then keep the text column as a separate table.
But a limit of 900 should be ok to keep as varchar.
its ok no problem using varchar(900) if you limited to store 900 character than no problem
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.