When a query runs against an InnoDB table, only the row s which are involved are locked, the rest of the table remains available for CRUD operations. This means queries can run simultaneously on the same table, provided they do not use the same row.
This feature in InnoDB is known as concurrency. As great as concurrency is, there is a major drawback that applies to a select range of tables, in that there is an overhead in switching between kernel threads, and you should set a limit on the kernel threads to prevent the server coming to a halt. MyISAM offers no data integrity - Hardware failures, unclean shutdowns and canceled operations can cause the data to become corrupt. This would require full repair or rebuilds of the indexes and tables.
InnoDB, on the other hand, uses a transactional log, a double-write buffer and automatic checksumming and validation to prevent corruption. Before InnoDB makes any changes, it records the data before the transactions into a system tablespace file called ibdata1. If there is a crash, InnoDB would autorecover through the replay of those logs.
In conclusion, InnoDB should be your default storage engine of choice. One more thing: you can backup InnoDB tables just by taking a snapshot of the filesystem. Basically, if you have another copy of the data and are only caching it in MySQL e. In my experience, the most significant difference is the way each engine handles locking. Before MySQL 5.
It is based on the older ISAM storage engine. MyISAM is optimized for environments with heavy read operations, and few writes, or none at all. The reason MyISAM allows for fast reads is the structure of its indexes: each entry points to a record in the data file, and the pointer is offset from the beginning of the file.
Thus, the rows are of constant length. A typical area in which one could prefer MyISAM is data warehouse, because it involves queries on very big tables, and the update of such tables is done when the database is not in use usually by night. Inserts are easy too, because new rows are appended to the end of the data file. However, delete and update operations are more problematic: deletes must leave an empty space, or the rows' offsets would change; the same goes for updates, as the length of the rows becomes shorter; if the update makes the row longer, the row is fragmented.
MySQL 5. XtraDB is maintained by Percona. Sign up to join this community. The best answers are voted up and rise to the top. Stack Overflow for Teams — Collaborate and share knowledge with a private group.
Create a free Team What is Teams? Learn more. Ask Question. Asked 10 years, 10 months ago. Active 4 years, 8 months ago. Viewed k times. Organization is half the battle, and that counts for all things digital too. A DBMS allows you to easily process, save, and permanently store large amounts of data. It is a storage subsystem and in recent years it has become one of the most popular choices thanks to its high levels of performance and reliability compared to other storage engines.
Does it have any disadvantages? Medium-sized and large companies choose the cloud from Germany. IaaS and PaaS are services for champions. Thanks to its combination of high performance and high reliability, it was made the default storage engine from Version 5.
A DBMS is a tool that allows you to store, index, and retrieve data in a table. MySQL can handle large volumes of reads and writes e. InnoDB provides MySQL with the storage engine needed to fulfil these functions, which operates as a module that can be easily integrated into the software. However, it is MySQL that determines how data is saved to a database. Databases consist of multiple tables, each of which is assigned to a specific storage engine like InnoDB when they are set up.
Most storage engines either store the data on a disk or keep it in the main memory for quick access. InnoDB implements isolated transactions which means data is only written to the corresponding storage medium when a specific transaction is complete. This ensures incomplete changes are not stored to the database.
Transactions are data packets consisting of a set of related operations that are treated as a whole. If any one operation cannot be completed, the entire transaction fails. The primary key uniquely identifies a row in a table. Every row in the table should have a primary key value, and no two rows can have the same primary key value. Typically, it is the most important column that you refer to in WHERE clauses when looking up a single row. Choose the column and its data type carefully.
Prefer numeric columns over character or string ones. Consider using an auto-increment column if there is not another stable, unique, non-null, numeric column to use. An auto-increment column is also a good choice if there is any doubt whether the value of the primary key column could ever change. Changing the value of a primary key column is an expensive operation, possibly involving rearranging data within the table and within each secondary index.
Consider adding a primary key to any table that does not already have one. Use the smallest practical numeric type based on the maximum projected size of the table. This can make each row slightly more compact, which can yield substantial space savings for large tables. The space savings are multiplied if the table has any secondary indexes , because the primary key value is repeated in each secondary index entry.
In addition to reducing data size on disk, a small primary key also lets more data fit into the buffer pool , speeding up all kinds of operations and improving concurrency. This design change can produce substantial space savings in the secondary indexes.
If you spread related information across multiple tables, typically each table uses the same column for its primary key. For example, a personnel database might have several tables, each with a primary key of employee number. A sales database might have some tables with a primary key of customer number, and other tables with a primary key of order number.
Because lookups using the primary key are very fast, you can construct efficient join queries for such tables. It is a 6-byte value that might be longer than you need, thus wasting space. Because it is hidden, you cannot refer to it in queries. If you set up a numeric ID column for the primary key, use that value to cross-reference with related values in any other tables, particularly for join queries.
For example, rather than accepting a country name as input and doing queries searching for the same name, do one lookup to determine the country ID, then do other queries or a single join query to look up relevant information across several tables. Rather than storing a customer or catalog item number as a string of digits, potentially using up several bytes, convert it to a numeric ID for storing and querying.
A 4-byte unsigned INT column can index over 4 billion items with the US meaning of billion: million. For the ranges of the different integer types, see Section You must not delete the ibdata files that represent the InnoDB system tablespace.
Methods of moving or copying InnoDB tables to a different server are described in Section Testing and Benchmarking with InnoDB. InnoDB Multi-Versioning. MyISAM won't enable you to do mysql level check. For instance if you want to update the imgId on both tables as a single transaction:.
Trust me, this really come at hand and is way less error prone. If answer to any of these questions is "yes", then you should definitely use InnoDB. Otherwise, you should answer the following questions :. Unless your tables are very large and you expect large load on your database, either one works just fine.
I would like to add something that people may benefit from: I've just created a InnoDB table leaving everything as the default, except changing the collation to Unicode , and populated it with about , records rows.
Stack Overflow for Teams — Collaborate and share knowledge with a private group. Create a free Team What is Teams? Collectives on Stack Overflow. Learn more. Ask Question. Asked 10 years, 1 month ago.
Active 4 years, 1 month ago. Viewed 8k times. Improve this question. This question begs debate IAbstract - You speak of something I'm unaware of but would be glad to oblige if you elaborate The way the question is asked will beg debate over which is better But since Programmers exists now and allows a greater deal of subjectivity in questions, seems like a better fit
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