One of the things we have been working on for MySQL 8, is speeding up scans that read multiple records from a table or an index. Such scans benefit from reading the records in batches, so that they don’t get the overhead of latching data pages and navigating in the B-tree for every single record that is read.…
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First, I want to thank everybody for attending the July 14 webinar. The recording and slides for the webinar are available here. Below is the list of your questions that I wasn’t able to answer during the webinar, with responses:
Q: At which isolation level do
copy data from a table?
A: Both tools do not change the server’s default transaction isolation level. Use either
MySQL 5.7.12 was released more than 2 weeks ago. New features
introduced there in a form of "rapid plugins" are widely
discussed, but I am more interested in bugs reported by MySQL
Community users that are fixed there. Unfortunately I do not see
MySQL Community Release Notes by Morgan (like this) for quite a some time, so I have to
continue describing key bug fixes and name people who reported
and verified bugs in my "Fun with Bugs" series.
As usual, let's start with InnoDB bugs fixed:
- Bug #80070 - "allocated_size and file_size differ if create general tablespace outside datadir". It was reported by my former colleague from Percona …
The optimizer in MySQL 5.7 leverages generated columns. Generated
columns will physically store data in two cases: Either the
column is defined as STORED or you create an index on a virtual
column. The optimizer will leverage such an index automatically
if it encounters the same expression in a statement. Let's see an
mysql> DESC squares;
| Field | Type | Null | Key | Default | Extra |
| dx | int(10) unsigned | YES | | NULL | |
| dy | int(10) unsigned | YES | | NULL | |
In a previous post I took the new JSON datatype and functions for a test drive, using sample data provided by SF OpenData. Today I will extend that example to include indexing.
Introducing Generated Columns
MySQL 5.7 introduces a new feature called generated columns.…
I've just noted that Oracle had released new versions of MySQL on
February 5, 2016 formally, so while these days I am mostly
thinking about the ways to do support properly, remembering my
colleagues and trying to understand some of RocksDB internals,
it's time to postpone all these and write about bugs again. This
time about some of the public bug reports from MySQL Community
and Oracle engineers that were fixed by Oracle in MySQL 5.7.11.
As usual, I'll try to mention who had reported a bug and who verified it, as I think that names matter in MySQL world. I'll concentrate mostly on InnoDB, replication and optimizer bug reports, trying to highlight regressions clearly.
As usual, I prefer to start with InnoDB bugs:
- Bug #75112 - …
I planned to continue this series of posts with the one about
MySQL Support engineers who joined us in Oracle while I was
working there, but based on recent events in my life I'd prefer
to postpone it and move directly to the team I worked for during
last 3+ years, Percona Support Team.
Disclamer: In the list below I still try to pay attention to public contribution by each of engineers mentioned to MySQL Community, mostly in a form of bug reports. This is not the only way they contributed, but I have to stick to this format in current series of posts. I also base my comments mostly on my memory and quick search of public sources of information, so I may be mistaking about the roles, time periods and other details. Please, inform me if you think there is something to fix.
So, here is the list of my former colleagues who formed the best MySQL Support team in the industry in 2013-2015 while working with me in …
I've got several useful habits over the years of work in MySQL
Support. One of them is to start working on every problem with
search for known MySQL bugs related to the problem at hand.
I'd like to share one recent case where this habit helped me to
get a solution for customer almost instantly.
It was one of rare cases when customer opened a support request with a very clear question and even a test case. The problem was described very precisely, more or less as follows (with table and column names, and data changed for this blog post, surely).
Let's assume we have two tables created like these:
mysql> create table t1(id int auto_increment primary key, c1 varchar(2), c2 varchar(100));Query OK, 0 rows affected (0.27 sec)
mysql> create table t2(id int auto_increment primary key, t1_id int, ctime datetime, cvalue decimal(10,2), key(t1_id, ctime));
Query OK, 0 …
MySQL 5.7.10, the first release after MySQL
5.7 GA announcement, appeared almost a week ago. It's interesting
to check what bugs reported by MySQL Community were fixed in this
version, hence this post (that had to wait during the weekdays
busy with usual support work). As usual, I'll concentrate mostly
on InnoDB, replication and optimizer-related bug fixes and
highlight names of those who reported and verified each
Let's start with InnoDB. The following bugs reported by MySQL Community users were fixed:
- Bug #78623 - "Small tablespaces with BLOBs take up to 80 times more space in 5.7 than in 5.6". This serious regression was reported by my colleague Laurynas Biveinis and verified by Umesh well before 5.7.9 …
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