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10 Newer Entries Showing entries 91 to 100 of 836 10 Older Entries

Displaying posts with tag: innodb (reset)

Getting to know TokuDB for MySQL
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During last April’s Percona Live MySQL Conference and Expo, TokuDB celebrated it’s first full-year as an open source storage engine. I still remember reading the official announcement and the expectations it created one year ago. The premises were very interesting as it had the potential of helping MySQL manage “big data” in a way InnoDB just couldn’t. It also provided additional interesting features like “hot schema changes,” all the while …

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InnoDB, The Choice for High Concurrency Database Systems
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InnoDB has proven to be a reliable data storage engine for modern, high concurrency database systems. It is fully ACID compliant, and supports a wide range of isolation modes, from READ-UNCOMMITEED to SERIALIZABLE.

InnoDB multiversion concurrency control (MVCC) enables records and tables to be updated without the overhead associated with row-level locking mechanisms. The MVCC implementation in InnoDB largely eliminates the need to lock tables or rows during updates, and enables good performance for high concurrency workloads.

To learn more about this subject and related performance tuning topics tuning, take the …

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ibdconnect and secondary keys
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ibdconnect is a tool to connect an ibd file to a foreign ibdata file. it’s important to understand how it works as secondary keys may cause interesting behavior.

Here is a table with a unique secondary key:

CREATE TABLE `t1` (
`id` bigint(20) unsigned NOT NULL AUTO_INCREMENT,
`value` varchar(255) COLLATE utf8_unicode_ci NOT NULL,
PRIMARY KEY (`id`),
UNIQUE KEY `uni_value` (`value`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8 COLLATE=utf8_unicode_ci;

When I update InnoDB dictionary with ibdconnect it all goes well:

# ./ibdconnect -f  t1.idb -o  /var/lib/mysql/ibdata1 -d test -t t1

… …








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Fun with Bugs #33 - bugs fixed in MySQL 5.6.19
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It seems Oracle released MySQL 5.6.19 yesterday. So, it's time to check what community bug reports are fixed there.

Let's start with InnoDB. We have the following bugs fixed:

  • Bug #72079, "Upgrade from 5.6.10 to 5.6.16 crashes and leaves unusable DB". Honestly I had not noted this bug, even though I upgrade several instances on Windows to each and every release since 5.6.8. Probably because I had no need to use FTS indexes till …



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Thanks, Oracle for fixing MySQL Bug 69477
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Just under a year ago, on June 14, 2013, I reported MySQL Bug 69477 (and MariaDB Bug MDEV-4662) titled “InnoDB: Use of large externally-stored fields makes crash recovery lose data”. The gist of this bug is that if you use large BLOB fields (> ~10% of your InnoDB redo logs size), you can compromise crash recovery and suffer data loss after a crash.

The MySQL bug was marked as “Verified” in less than an hour (wow!), but since then there was not a single word about it. Suddenly a couple of …

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How important is it to use 2-byte and 3-byte integers?
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One interesting feature of MySQL, is that it supports a very large number of integer data types. From the MySQL manual:

Type Storage Minimum Value Maximum Value
(Bytes) (Signed/Unsigned) (Signed/Unsigned)
TINYINT 1 -128
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A technical WebScaleSQL review and comparison with Percona Server
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The recent WebScaleSQL announcement has made quite a splash in the MySQL community over the last few weeks, and with a good reason. The collaboration between the major MySQL-at-scale users to develop a single code branch that addresses the needs of, well, web scale, is going to benefit the whole community. But I feel that the majority of community opinions and comments to date have been based on the announcement itself and the organizational matters only. What we have been missing is an …

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MySQL-5.7 improves DML oriented workloads
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In MySQL 5.7, we have improved the scalability of DML oriented workloads in InnoDB. This is the result of a number of changes, which I will outline below.

(1) Fix index->lock contention

This RW lock protects all indexes, both the cluster and the secondary indexes.

Before 5.7, every modifications to non-leaf pages (every modifications for the tree structure) required to exclude the other threads’ access to the whole index by X-lock, and every concurrent accessing the index tree were blocked. This was the major reason of the index->lock contention in concurrent DML workloads.

In MySQL 5.7 concurrent access is …

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InnoDB with reduced page sizes wastes up to 6% of disk space
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In InnoDB bugs found during research on InnoDB data storage I mentioned MySQL Bug #67963 which was then titled “InnoDB wastes 62 out of every 16384 pages”. I said:

InnoDB needs to occasionally allocate some internal bookkeeping pages; two for every 256 MiB of data. In order to do so, it allocates an extent (64 pages), allocates the two pages it needed, and then adds the remainder of the extent (62 free pages) to a list of extents to be …

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Rankings with InnoDB Full-Text Search
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Summary
Since MySQL 5.6 went GA—where among many other new features, we introduced full-text indexes for the InnoDB storage engine—questions have occasionally come up about InnoDB full-text search relevancy rankings when doing BOOLEAN MODE searches. Typically these questions revolved around a core issue: why do the results differ from that of MyISAM? In short, the InnoDB document search and relevancy rankings were modeled after the open source …

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10 Newer Entries Showing entries 91 to 100 of 836 10 Older Entries

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