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The first situation often corresponds to Innodb spending a lot of CPU time running “loops” as part of spinlock implementation. In many cases busy wait is indeed more efficient than doing context switches, however sometimes there is just too much spinning and it becomes inefficient. Reducinginnodb_sync_spin_loops variable to a smaller value is known to help in some of those cases.

The second situation corresponds to a lot of context switches being done, which well may be normal – if your workload has large portion of “critical section” where only one thread can be working at a time, you should expect a lot of threads waiting and the more CPU cores you have available the less CPU utilization you can have. Sometimes though you may be wasting time with context switching because Innodb is not spinning too much, thus you can consider increasing innodb_sync_spin_loops to a higher number.

But then, I’ve discovered there is a flag called NO_BACKSLASH_ESCAPES:

http://dev.mysql.com/doc/refman/5.7/en/server-sql-mode.html#sqlmode_no_backslash_escapeshttp://stackoverflow.com/questions/9428087/disable-escape-characters-in-a-mysql-query

This just reminds me of PHP’s horrible magic quotes. In fact, combine arbitrary configurations of PHP and MySQL on your server and good luck to you of ever getting string literals right.

The XML Query Working Group and the XSLT Working Group have published five Proposed Recommendations today:

XQuery 3.0: An XML Query Language. XQuery is a domain-specific language for querying collections of XDM trees.XML Path Language (XPath) 3.0. XPath is a domain-specific language for referencing parts of a tree represented as an instance of the XPath and XQuery Data Model (XDM).XQuery and XPath Data Model 3.0.This specification defines the XPath and XQuery Data Model (XDM).XPath and XQuery Functions and Operators 3.0. The Functions and Operators specification defines facilities for XPath and XQuery.XSLT and XQuery Serialization 3.0. Serialization specifies how to represent an XDM instance as XML, as HTML or as text. The XDM is most often used to represent XML documents as trees, but can also represent other data formats such as JSON, RDF or relational databases.

Comments are welcome through 19 November. Learn more about the Extensible Markup Language (XML) Activity.

Thank you, Oracle team, for finally fixing this bug (even though you’re about 6 years late). Here are two pieces of advice to prevent this error from happening:

Use consistent data types. Make sure you’re using consistent data types for the same values. Often it's just better to standardize a few and to not make a decision in every single case. I, for example, use “int unsigned not null” for positive intergers that aren't too big.

Consider using strict mode. Storing different data types when your application requests without throwing the error out is not a good idea in most cases, yet MySQL continues to be very loose by default. Consider running with sql_mode=strict_all_tables which will report the error when data is truncated, along with using transactional tables for any data you value.

 

In MySQL, you can legally execute the following statement:

1234SELECT o.custid, c.name, MAX(o.payment)  FROM orders AS o, customers AS c  WHERE o.custid = c.custid  GROUP BY o.custid;

The statement was taken from here:
http://dev.mysql.com/doc/refman/5.6/en/group-by-hidden-columns.html

So what does this statement even mean? What will be returned in the c.name projection? MAX(c.name)? ANY(c.name)? FIRST(c.name)? NULL? 42? According to the documentation, ANY(c.name) would best describe what’s going on. This peculiar syntax is probably quite clever for those few that really know when this is useful. When they know exactly, that o.custid and c.name have a 1:1 correlation, and they can speed things up a little by avoiding writing things like MAX(c.name), or by adding c.name to the GROUP BY clause (“yes, saved yet another 8 characters”).

But the bulk of newbie MySQL users will be confused by this.

FeaturesAutomated generation of test dataAjax based Rich UI by VAADIN Framework20+ Data types supportedSQL, CSV, XML, EXCEL Data generationInstant SQL Script RunnerExport to File feature for generated DataDatabase Explorer tabConfigurable Data FormatsConfigurable Database settingsSingle sign on Database connectionTable Data Export/Import featureComplete Help and Tutorials provided