![]() ![]() Besides the quadruple disk space used, which may be largely negligible after additional data is added, they appear to me to be the same. What I am essentially trying to discover is difference in efficiency between the two approaches. This means that the storage requirements are different - a CHAR always takes the same amount of space regardless of what you store, whereas the storage requirements for a VARCHAR vary depending on the specific string stored. The use case for this type of set up would be the traditional primary key for inter-table relationships, with unique identifier used for inter-system relationships. sisve i think mysql encourage to store 128 bit data in binary, mysql have no support for ipv6 but it have function to convert ipv6 to binary and vice versa the same as with uuid, because mysql has function to convert binary to uuid so i think mysql recommend storing uuid in binary, no need for native data type if it can do the same just with. A CHAR field is a fixed length, and VARCHAR is a variable length field. Whereas many people stress over the advantages of either, what are the disadvantages cancelled out by using both data types? I was initially sceptical towards using UUIDs as primary keys, and indeed I still am, however I see potential here to create a flexible database that can use both. The test and results are shown below, but if you just want the summary, it indicates that INT AUTOINCREMENT and BINARY(16) RANDOM have identical performance on data ranges up to 200,000 (the database was pre-populated prior to tests). It was when I reached the final one BINARY(16) that I started to compare performance with basic auto-increment integer. The formats I used changed as I became less naive from: Now, we create our domain class using Hibernate annotations to map it to our existing MySQL table. While doing this, I discovered that about half our UUIDs are v1, and the other half are v4. I was recently asked to add a column to this table of VARCHAR(32) that stores the non-dashed UUID hex. ![]() They are stored in the standard VARBINARY(16). The rest of the table structure can be similar to the image. I have a MySQL InnoDB table with tens of millions of rows. You then use UUIDTOBIN () or BINTOUUID () to convert from binary to the text human readable UUID stuff. That means compressing the 32 characters (36 or more with separators) to the 16-bit format or back to the human-readable format. You can store as CHAR (36) or store as VARCHAR (36) (both make sense) or store as STRING (probably better to use CHAR (36)) but you can store it as BINARY (16) as well. It is designed in such a way that it generates a number which is unique globally according to space and time. I've been using UUIDs in my systems for a while now for a variety of reasons ranging from logging to delayed correlation. Since we know the format of the UUID when represented as a String, we know that it has a length of 36 characters, so we can define the column as VARCHAR (36). These function will be used to convert from the human-readable format (char/varchar) to the compact format (binary) and back. A UUID is a Universal Unique Identifier specified by RFC 4122 (It is a Universally Unique Identifier URN Namespace) and 128-bit long value. ![]()
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