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10 Newer Entries Showing entries 31 to 40 of 1010 10 Older Entries

Displaying posts with tag: sql (reset)

WITHer Recursive Queries?
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Over the past few years, we’ve seen MySQL technology advance in leaps and bounds, especially when it comes to scalability. But by focusing on the internals of the storage engine for so long, MySQL has fallen behind regarding support for advanced SQL features.

SQLite, another popular open-source SQL database, just released version 3.8.3, including support for recursive SQL queries using the WITH RECURSIVE syntax, in compliance with SQL:1999.

Why is this significant? It means that MySQL is now the …

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Unittesting your indexes
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During FOSDEM PGDay I watched the "Indexes: The neglected performance all-rounder" talk by Markus Winand. Both his talk and the "SQL Performance Explained" book (which is also available online) are great.

The conclusion of the talk is that we should put more effort in carefully designing indexes. But how can we make sure the indexes are really used now and in the future? We need to write some tests for it.

So I wrote a small Python script to test …



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MariaDB 10: Performing fast & inaccurate statistics
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As I already wrote, COUNT(*) can be expensive in InnoDB, because this value is not stored in indexes. Some other storage engines may not store that value. Also, COUNT(), MAX(), MIN() are immediate only if executed on an indexed column. But we don’t want too many indexes, and some exotic storage engines do not support indexes – thus, we may need to execute an aggregate function on a non-indexed column.

Now, the question is: do you really need such values to …

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Immutability, MVCC, and garbage collection
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Not too long ago I attended a talk about a database called Datomic. My overall impressions of Datomic were pretty negative, but this blog post isn’t about that. This is about one of the things the speaker referenced a lot: immutability and its benefits. I hope to illustrate, if only sketchily, why a lot of sophisticated databases are actually leaps and bounds beyond the simplistic design of such immutable databases. This is in direct contradiction to what proponents of Datomic-like systems would have you believe; they’d tell you that their immutable database …

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New! MySQL Utilities release-1.3.6 GA
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The MySQL Utilities Team is pleased to announce the latest GA release of MySQL Utilities. This release includes a number of improvements for usability, stability, and a few enhancements. We have also included a performance upgrade for exporting, importing, and copying databases.

Improvements
The following highlights a few of the more significant improvements.

* mysqldbexport, mysqldbimport, and mysqldbcopy have multiprocessing support that allows for much improved performance
* mysqlfrm can now generate a .frm file with storage engine substitution
* Mac OS X packages added!
* …







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How is the MariaDB Knowledge Base licensed?
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I clicked around for a few moments but didn’t immediately see a license mentioned for the MariaDB knowledgebase. As far as I know, the MySQL documentation is not licensed in a way that would allow copying or derivative works, but at least some of the MariaDB Knowledge Base seems to be pretty similar to the corresponding MySQL documentation. See for example LOAD DATA LOCAL INFILE: MariaDB, MySQL. …

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Props to the MySQL Community Team
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Enough negativity sometimes gets slung around that it’s easy to forget how much good is going on. I want to give a public thumbs-up to the great job the MySQL community team, especially Morgan Tocker, is doing. I don’t remember ever having so much good interaction with this team, not even in the “good old days”:

  • Advance notice of things they’re thinking about doing (deprecating, changing, adding, etc)
  • Heads-up via private emails about news and upcoming things of interest (new features, upcoming announcements that aren’t public …
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S**t sales engineers say
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Here’s a trip down memory lane. I was just cleaning out some stuff and I found some notes I took from a hilarious MySQL seminar a few years back. I won’t say when or where, to protect the guilty.[1]

I found it so absurd that I had to write down what I was witnessing. Enough time has passed that we can probably all laugh about this now. Times and people have changed.

The seminar was a sales pitch in disguise, of course. The speakers were singing Powerpoint Karaoke to slides real tech people had written. Every now and then, when they advanced a slide, they must have had a …

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EXPLAIN UPDATE in MySQL 5.6
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I just tried out EXPLAIN UPDATE in MySQL 5.6 and found unexpected results. This query has no usable index:


EXPLAIN UPDATE ... WHERE col1 = 9 AND col2 = 'something'\G
*************************** 1. row ***************************
           id: 1
  select_type: SIMPLE
        table: foo
         type: index
possible_keys: NULL
          key: PRIMARY
      key_len: 55
          ref: NULL
         rows: 51
        Extra: Using where

The EXPLAIN output makes it seem like a perfectly fine query, but it’s a full table scan. If I do the old trick of rewriting it to a …

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MySQL Synonym?
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Somebody asked how to create a SYNONYM in MySQL, which is interesting because MySQL doesn’t support synonyms. I thought the prior entry explained how to do it, but here’s a new post. However, you can create a view in one database that relies on a table in another database.

The following SQL statements create two databases and grant appropriate privileges to the student as the root superuser:

/* Create two databases. */
CREATE DATABASE seussdb;
CREATE DATABASE appdb;
 
/* Grant …
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10 Newer Entries Showing entries 31 to 40 of 1010 10 Older Entries

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