PostgreSQL

Courtesy the United States PostgreSQL Association, the big news: PostgreSQL 8.4 Released!.

Josh Berkus writes, “Now that PostgreSQL 8.4 is out, I thought I’d write a little about my favorite 8.4 feature. As Mr. Performance Whack-a-Mole, what makes me happy about 8.4 is the ability to whack moles faster … which is why I’m very fond of pg_stat_statements.”

On ad’s corner, Andreas Scherbaum says, “Up to PostgreSQL 8.3 it was only possible to grant (and revoke) permissions on the entire table. If column level permissions were needed, a workaround like a view solved (more or less) the problem . . .  This . . . is uneloquent, error prone and does not scale well.  . . .  PostgreSQL 8.4 solves the problem with a shiny new feature: column level permissions.”

David Fetter looks into WITH (so much drama in the CTE): ” By now, you’ve probably seen that PostgreSQL 8.4 can produce Mandelbrot sets . . . but what are Common Table Expressions really about? [They] are just views you create at run time. Oh, and they can refer to themselves. That latter capability is powerful and flexible (read confusing), so I’ll go over that one later. Run-time views are pretty handy, though.”

Andrew’s PostgreSQL blog introduces parallel pg_restore for PostgreSQL 8.4: “I try to complete at least one significant feature item per PostgreSQL release. This time the feature is making pg_restore run in parallel. This is quite important for many users, particularly some large enterprise users.”

SQL Server

Eric Johnson introduces SSIS 2008 and the new lookup: “SSIS is a pretty useful tool for designing ETL processes. One of the transformations I was disappointed with in 2005 was the lookup. I found it a little better than the lookup functionality in DTS, but not too much better. Well, Microsoft must have read my mind because SQL Server 2008 has a new shiny Lookup transformation that is, in my opinion, much improved.”

Kimberly L. Tripp was thinking about looking for security vulnerabilities in database code. “I’ve always been concerned with security and I’ve always stressed the importance of auditing the REAL user context not just the current user . . .  So, I generally try to avoid using dynamic string execution and if necessary create well tested/protected parameters . . .  Having said that, what if I’m looking at a database for the first time . . .  I’ve come up with a quick query… And, while it’s not going to “solve” your problem . . . or even truly verify if you’re vulnerable, it gives you a ‘quick list’ of where you should look first! ”

Adam Machanic exposed the hidden costs of INSERT EXEC, beginning, “INSERT and EXEC: relational brothers in arms, helping you get your data and then put it somewhere. But like all brothers, their relationship has its ups and downs and sometimes you need to look just below the surface to see the real issues. In this post I will cover hidden penalties that a decision–seemingly purely aesthetic–can bring to the fore.”

Martin Bell offered the reminder, after disabling TDE you still requires the certificate to restore the database.

Data Management has a first-rate HOWTO on dynamic column names and fields in SSRS. “I had no choice but to do work with creating dynamic column headings and dynamically determine what field in my dataset should go where in a report today. Sense [sic] this is the second time I’ve gone through this exercise and knowing the lack of information out there on really how to do it, I thought it deserves a blog entry.  . . .  So here is the basis of the requirements. You have a query that uses PIVOT but thrown into the mix is the need for dynamic columns in the PIVOT.”

MySQL

Here on the Pythian Blog, Sheeri Cabral expressed some concerns and what does not work in XtraDB backup.

On xaprb, Baron Schwartz has a review of MySQL Administrator’s Bible. “I think that MySQL Administrator’s Bible is a very good complement to High Performance MySQL, 2nd Edition. The former is useful to people who have varying levels of knowledge, while the latter assumes a lot of experience and doesn’t cover introductory material much.  . . .  So if you’re new to databases, or if you’re new to MySQL, you might do well to start with Sheeri’s book . . . ”

Over on the MySQL Performance Blog, Baron looked into gathering queries from a server with Maatkit and tcpdump: “For the last couple of months, we’ve been quietly developing a MySQL protocol parser for Maatkit. It isn’t an implementation of the protocol: it’s an observer of the protocol. This lets us gather queries from servers that don’t have a slow query log enabled, at very high time resolution.”

Ronald Bradford looked at verifying MySQL replication in action, with “ . . . a very simple test to show MySQL replication in action and to also better understand the basics of MySQL Replication. With a configured MySQL environment we can run the following test on your MySQL master, and monitor the MySQL slave.”

The MySQL Workbench Team Blog says, Time To Upgrade - MySQL Workbench 5.1 Is Here on Win, Mac & Linux. Perty pictures follow.

Oracle

H. Tonguç Yilmaz asserted, Instrumented Code is Better: An Example on How to Generate Session Level ASH Reports. ” After 10g if you have its license ASH based performance monitoring is an alternative to the traditional SQL Tracing in my opinion. You may either use EM to generate ASH reports or directly query ASH dictionary. The handy additional hint here is that you can set filters to ASH data in order to focus on a specific session, the filter options at ASH report screen at EM can be used for this purpose or below is an example to monitor the waits from v$active_session_history view.”

Doug Burns responded with his item on session-level ASH reports: “I think [Tonguç's] post is really showing two different things, one more successfully than the other.”

Randolf Geist reports a Dynamic sampling and set current_schema anomaly: “If I’m now supposed to analyse a rather complex SQL with dozens of table and/or view references I like to use the ALTER SESSION SET CURRENT_SCHEMA command . . .  This basically works just fine, but I recently have come across an interesting anomaly in 10.2.0.4: If the optimizer uses dynamic sampling as part of the parsing then it doesn’t do so anymore if the CURRENT_SCHEMA has been altered to a non-default schema.”

On the Oramoss Blog, Jeff Moss looks at the case of no pruning for MIN/MAX of partition key column: “Recently, I wanted to work out the maximum value of a column on a partitioned table. The column I wanted the maximum value for, happened to be the (single and only) partition key column. The table in question was range partitioned on this single key column, into monthly partitions for 2009, with data in all the partitions behind the current date, i.e. January through mid June were populated. There were no indexes on the table.” Jeff and his readers examine the evidence and discuss some workarounds to the problem.

Oracle, MySQL, PostgreSQL, SQL Server. How’bout . . . 

NoSQL

(No SQL?!? Edwards, you’re mad!) Well, it’s not me. Here’s Curt Monash on NoSQL: “Eric Lai emailed today to ask what I thought about the NoSQL folks, and especially whether I thought their ideas were useful for enterprises in general, as opposed to just Web 2.0 companies. That was the first I heard of NoSQL, which seems to be a community discussing SQL alternatives popular among the cloud/big-web-company set, such as BigTable, Hadoop, Cassandra and so on.”

PostgreSQL stuff also had some thoughts on those who say No to SQL. “Every time I see something or hear something like this I sigh a little bit. Not only when it’s related to SQL but in the world of computer professionals in general. ‘The right tool for the job’ seems to be a hard concept to understand sometimes. I wonder why?”

Back to Oracle for a moment. Tanel Poder has a secret preview of Oracle 12g CBO leaked from Oracle labs. Would you like fries with your cost-based optimizer?

That’s all for now. See you in a week’s time!

Jonathan Lewis writes, “It occurred to me recently that I might be making casual use of terms that weren’t necessarily very well known to the less experienced user. So I’ve decided to build a glossary of terms – and I’ll try to add to it from time to time whenever I have a few minutes.”

Jonathan might want to add “Method R” to the glossary. Cary Millsap was making it understood, as he shows in Profiling with my Boy: “Today I’m going to raise the stakes, because yesterday I think I explained Method R so that an eleven year-old could understand it.”

Vivek Sharma offers a thorough look at the Cost-Based Optimizer: Inefficient Input yields Inefficient Output. Vivek begins, “Cost Based Optimizer has always been a mystery for most of the Database Administrators and Developers.  . . .  Cost Based Optimizer has improved a lot in previous few versions. Therefore, it can be said that CBO is still undergoing some enhancements. With these enhancements, Oracle Users have accepted the fact that the Application Performance might degrade after version upgrade . . . ”

Randolf Geist had some info to share on the matter of locked table statistics and subsequent create index. “ . . . in 10g and later index statistics are generated along with an index creation  . . .  so a newly created index usually has computed statistics. 10g also introduced the option to lock table statistics. Now if you lock statistics in 10g in later  . . .  and create an index on a locked table the statistics for the index will not be generated along with the CREATE INDEX command.”

Rob van Wijk gave us part three of his series on fast refreshable materialized view errors: aggregate MV’s. “In the third part I’m going to examine all restrictions for aggregate materialized views, as described in the documentation.  . . .  So this will be quite a lengthy and even tedious post, as you can imagine by the list above … but for a good cause.”

In MySQL blogs, the MySQL Performance Blog announced Percona.tv. Ryan Loew writes, “We’ll be uploading technical screencasts, conference video, and anything else cool we can think up.”

The Open Query blog published Good Practice/Bad Practice: Table Aliases. “When writing queries, try making a habit out of using short table aliases, no matter how small the query is.” An example using the World DB follows, as does a worthwhile discussion.

Roland Bouman examined MySQL stored functions: the impact of DECLARE HANDLER on performance, responding to Get the error return value in a variable by Peter Gulutzan.

Ronald Bradford looked into using statpack with SHOW STATUS. He writes: “Mark Leith, on of the MySQL Support Team managers wrote some time ago a very nice utility I use often called Statpack.  . . .  Over time I’ve grown to love it’s simplicity, but notice a number of shortcomings.  . . .  This post is more about detailing those little annoyances that I’d like to improve, or see improved.”

Morgan Tocker writes, “I think 5.1 gets some bad press for not being a compelling upgrade. It’s not the big features that make the difference, but the subtle ones. I wanted to highlight some of the these that may make your life easier when it’s time to upgrade . . . ” The post is Hidden gems in 5.1.

Let’s turn to SQL Server now, starting with a post from Aaron Alton, The HOBT. He writes, “If you’ve been working with SQL Server for any length of time, you’ve probably seen a number of different variations of the UPDATE command.  . . .  Anyway, today’s blog post is more like a public service announcement. It seems that all too many developers are still dangerously unaware of the ability to create very ambiguous UPDATE statements in TSQL.” Click through for Tricky Updates: Weird, Wacky, and Wonderful UPDATE Syntax Variations in SQL Server.

Louis Davidson looked into the question of read/write ratio versus read/write ratio. That’s what it says, really.

Alexander Kuznetsov posted one of those skill-testing quizzes—calculating third Wednesday of the month with inline UDFs. Alexander begins, “Problems such as calculating third Wednesday of the month or the last day of the month are very common. Recently Peter Larsson posted a scalar UDF that solves problems such as ‘third Wednesday of the month’, and Uri Dimant added a comment with a solution by Steve Kass. Unfortunately, all these solutions use scalar UDFs and as such are very slow, so I decided to post some very fast inline UDFs that I find very useful.”

Linchi Shea also was working the paradoxes: Performance impact: Logical scan fragmentation — 100% may not be as bad as 85%. “In [a] previous post I asked whether 100% logical scan fragmentation is always worse than 85% local scan fragmentation for table/index scans.  . . .  The answer is no. 100% logical scan fragmentation is not always worse than 85% logical scan fragmentation in terms of table or clustered index scans. And the following is an example.”

Reading is cool. I learned this from the Fonz. But look at this, Jeremiah Peschka says there are circumstances when less reading is a good thing. I’m confused! What else does he say? “Less reading is a good thing when you’re reading from a physical disk.” Ahhh. “During some recent performance tuning, I stumbled across a little gem of a stored procedure that was producing between 4,000 and 11,000 physical reads every time it was called.  . . .  It returns a list of state abbreviations. I’m not proud to say that I wrote it, but I have to come clean: I wrote it. So, how did I fix this travesty of my youthful ignorance?” I bet he hits his server machine in just the right way.

In PostgreSQL blogs, David Wheeler and his readers discussed the pgTAP Set-Testing Update.

The Postgres OnLine Journal exposed a restore of functional indexes gotcha.

In the DB2 world, Craig Mullins advised: know your ISOLATION levels. Craig writes, “Did you know that DB2 provides a way to change the way that a program or SQL statement acquires locks? That way is known as the isolation level and it can be set to specify the locking behavior for a transaction or statement.”

Willie Favero published the second of a couple articles collecting resources for both DB2 z/OS and DB2 LUW.

That’s all for now. Please add your favourite blogs from this week to the comments. And of course, don’t forget that you can publish an edition of Log Buffer on your own blog. Just send me an email to get started.

Till next time!

Many people other than Dave are finding release this week. Giuseppe Maxia explains some details of MySQL’s New Release Model. Andrew Morgan announces a New MySQL Cluster Maintenance Release. Aleksandr Kuzminsky of the MySQL Performance Blog releases build16 of the Percona MySQL binaries (versions 5.0.77 and 5.0.82), which adds some 5.4 features and fixes some bugs.

Darran Cassar, the MySQL Preacher, has created a package for Security Roles and Password Expiry on MySQL. And for a future MySQL release, look for Two New Status Variable Patches, for query invalidation count and a last received datetime for replication heartbeat. These patches were contributed by MySQL Support Team member Andrew Hutchins.

Dave Beulke points out a new feature in DB2 9.7 — DB2 Compatible with Oracle.

To prepare for a future SQL Server release where CREATE DEFAULT, sp_bindefault and sp_unbindefault will be deprecated, Martin Bell advocates Changing Bound Defaults to Default Constraints. If you are going to upgrade SQL Server, definitely look at the notes from SQL Master of SQL Server QA’s presentation on SQL Server Upgrade Issues and How To Evaluate Potential Issues.

Stewart Smith lets is know that Drizzle Tarballs for the Next Milestone - Aloha are being released weekly. Meanwhile, Jay Pipes and the rest of the Drizzle team find, fix and explain the cause of a performance regression in Drizzle Performance Regression Solved - TCMalloc vs. No TCMalloc.

Lenz Grimmer has started organizing OpenSQLCamp 2009, Aug 22-23 in Germany; he posts details and links in Speaking at FrOSCon and Organizing the OpenSQLCamp 2009, European Edition. If you want to speak, Lenz also lets you know that Ronald Bradford gives out a discount code and reminds us that we can still attend OSCon 2009 at a Discounted Rate (until June 23rd). OSCon 2009 will be held July 20-24 in San Jose, California. And in Iowa, Michelle Ufford sends out the East Iowa SQL Saturday Call for Speakers to be held on Saturday, October 10, 2009.

Getting back to basics, Richard Foote explains Oracle’s cost-based optimizer in CBO and Indexes, an Introduction for Absolute Beginners. Speaking of optimizations, Valcora has Another Way To Do Performance Tuning — make sure you actually need the queries that are running against your system!

Tanel Poder points to a blog post on Using Perfsheet and TPT Scripts for Solving Real Life Performance Problems in an Oracle RAC environment. And Jonathan Lewis provides a script you can run if you are concerned about the potantial of Oracle PGA leaks. Over at Oraclue, Miladin Modrakovic shows how to discover memory “leaks and other problems with allocations of memory” in Memory Annotations and Oradebug.

If you are migrating a database from Oracle to MySQL, you may be interested in George Trujillo’s process of Converting an Oracle Schema to MySQL.

Kimberly L. Tripp reveals a lot of information about how SQL Server optimizes queries and common myths when she reveals The Tipping Point Query Answers. David Fetter shares Materialized Views Performance Tips in Postgres, and Leo Hsu and Regina Obe talk about Planner Statistics in the Postgres optimizer.

In the land of DB2, Henrik Loeser shares a PureXML Performance Tip: A Sequence of Good Indexes.

Coskan explains
How to Use Sysman Schema Without Oracle Enterprise Manager. John Hallas notes that using Oracle’s EM to migrate a database to ASM is easy, but seems slow, in ASM Metadata and Migrating a Database to ASM. He then goes on to share a coworker’s Script to Backup ASM Metadata. J. Arneil shows how to go about Fixing up ASM Disk Header Corruption, should you find yourself in a rough spot.

Aaron Alton has a great article telling us that in Defensive Programming, Assumptions Must be Guaranteed or Tested, and another one on handling tags efficiently in Full Text Search vs. Denormalized Tables Remus Rusanu provides a Transact-SQL stored procedure template for Exception Handling and Nested Transactions.

I’ll end with a link to another survey on What’s the hardest part of becoming an involuntary DBA? It’s one simple question, so go fill it out! You have the time, especially since Craig Mullins points out that on average, we got a 4.6% salary increase in 2008 in Salaries for Data Professionals Inching Upward. To learn more and become even better in your field, get a 15-day free trial to Safari Books Online from O’Reilly, with a 15% discount if you continue past the free trial, courtesy of Susan Visser.

MySQL

Let’s begin with the big-picture stuff. Jeremy Zawodny laid out his view of the state of MySQL in Linux Magazine’s blog, noting the rough transition between versions 5.0 and 5.1, the status of storage engines, and outside contributions.

Like Baron Schwartz’s Maatkit, for example. Baron announced this week that he is writing a book about Maatkit, and also seeking input for a new tool to verify MySQL upgrades.

Percona is surely one of the foremost outside contributors in the MYSQL world. This week on their MySQL Performance Blog, Peter Zaitsev and his readers discuss some ad hoc ways to copy a database, in his item on using netcat to copy MySQL Database.

Darren Cassar, MySQL Preacher, delved into the particulars of replicating from MySQL to *. “Unsurprisingly there are quite a few different tools to do it from any platform towards MySQL but very few which do it the other way round . . .  I decided to have a look at doing the job myself. Although it might look an overkill to do so, it took me a few hours to find a solution and implement it and a couple more to test it and here is a simple description.”

As for engines, Mark Callaghan contributed a fine blog on the performance impact of prefetching in InnoDB. Mark writes, “There isn’t much data to indicate when this feature should be enabled. I have published data for a few IO-bound benchmarks. On these tests, the prefetching done by InnoDB reduces performance.”

A extensive discussion of security—vis-a-vis MySQL—took place this week. Ronald Bradford got it started with his item on basic OS/MySQL security. Followed by more basic MySQL security: “Never store the MySQL ‘root’ user password in a ~root/.my.cnf file.” That does seem pretty basic, doesn’t it. And yet it needs restating.

Lenz Grimmer responded with his thoughts on providing passwords on the command line. And with more on MySQL password security.

Ronald also got a lot of entries to his (now closed) contest for MySQL DBA fame and glory. The matter: what five settings would you add to redeem a very minimal my.cnf. (Here’s Ronald’s post with the winner.)

SQL Server

Sticking, for a moment, with the contest theme, Adam Machanic announced and explained the winning entries to his grouped string concatenation challenge from February.

On Claypole’s World, James Roland Jones presents The Curious Case of the Dubious Deadlock and the Not So Logical Lock. The scene is set thus: “My latest engagement has involved working with one of the largest Teradata installations in the world . . .  To give you an idea of the scale; this system has over 40 Billion rows in just one of the fact tables… 40. Billion. That’s a lot of rows. During this engagement we encountered a rather bizarre issue that doesn’t seem to be well understood so I thought I’d blog about it. Get ready for a mind job…”

The rusano.com blog gave their response with %%lockres%% collision probability magic marker: 16,777,215.

On the Less Than Dot blog, SQLDenis asserts: your testbed has to have the same volume of data as on production in order to simulate normal usage, and shows exactly why.

Paul S. Randal was clearing up misconceptions around the log and log backups, which he begins so: “There’s still a widely held misconception that when properly in the FULL or BULK_LOGGED recovery models that full or differential backups can truncate the log. No. It *NEVER* happens. This is one of the reasons why I’m doing a whole spotlight session on this at PASS this year - the transaction log and its behavior is IMHO one of the most misunderstood parts of SQL Server.”

Lubor Kollar of the SQL Server Development Customer Advisory Team compared several methods of fast ordered delete, one of MySpace’s Senior Database Developer Kevin Stephenson’s “pain points”.

PostgreSQL

Let’s create a little friction and jump straight to Postgres-vs.MySQL. Robert Treat shares the first rule of Postgres Club. No, I’m not going to give it away—you’ll just have to read Robert’s post. Suffice it to say, though, that is has to do with Postgres advocacy and knowing when not to do it.

Robert also shares video of his PGCon ‘09 presentation, Guide to Postgres 8.4.

Magnus Hagander describes his way of getting a range of entries centered around a point.

Oracle

Nuno Souto says that size sometimes does matter. I’m way above getting attention from that sort of double-entendre, but what he’s talking about, in fact, is optimal memory limits for Oracle under AIX, at which he takes a long, hard look.

Dion Cho writes, “Similar cursor sharing and multiple child cursors are very common problems . . .  What makes people confused about simiar cursor sharing is this. What the hell does ‘SIMILAR’ mean exactly?”

Tanel Poder, for his part, was diving into the shared pool and coming up with answers, his post, ORA-04031 errors and monitoring shared pool subpool memory utilization with sgastatx.sql

Here on the Pythian blog, Alex Gorbachev showed how to dynamically call a PL/SQL procedure.

On the AMIS Blog, Gerwin Hendriksen discussed enhancing fast queries using “tapio-indexes”, a.k.a “fat indexes”.

And you know what? I’ve got more blogs, but no more time. Let’s hear your favourite blogs in the comments! See you for LB#150!

PostgreSQL

Since PGCon ‘09 has concluded not long ago (and not far away), let’s start with Postgres stuff, much of which has to do with the convention.

Here are Robert Treat’s reflections on PGCon 2009, on his zillablog: “ . . . PGCon always presents the strongest line up of Postgres information available, and this year was certainly no exception.”

Josh Berkus was there, of course, and he sends two detailed reports: pgCon 2009 part 1, and part 2.

tail -f /dev/dim has a review of PGCon 09: “ . . . I found the experience to be a great one . . . ”

Magnus Hagander has shared his pgcon photos.

Jignesh Shah reports on the upshot of some interaction at his PGCon presentation, “ . . . it is highly recommended specially on multi-core systems to use FX scheduler class for Postgres on OpenSolaris.”

Back to Josh and his readers now for a worthwhile discussion of PostgreSQL development priorities. Josh’s #1: “Simple built-in replication.”

SQL Server

Pinal Dave has assembled a SQL Server Cheat Sheet and kindly shares it with all of us.

Linchi Shea has an update to his T-SQL exercise, to produce the simplest data-loading script to produce worst query performance. “The original intent,” writes Linchi, “was to highlight some pitfalls in data loading that may lead to bad query performance. But then I thought why take all the fun away by having too many constraints, and why not just let it loose and see how bad it can get if one is to do it intentionally.”

Aaron Alton, the HOBT, was likewise thinking on ways the SQL DBA goes awry. His conclusion: easy on the updates there, sparky. “To the unsuspecting database developer, it may seem that some operations in SQL Server are more or less ‘free’. Let’s clear the air on that one – nothing is free, ever. Or if it is, it usually has a 30 day limit. It’s easy to forget this, because when you’re working with something like SQL Server, it’s hard to imagine that a sub-second response time can hide anything of significant concern.”

Sometimes you don’t need to make things bad intentionally. For example, when a decimal isn’t a decimal. Simon Sabin writes, “To say the type system in SQL is lax is an not quite correct, its actually lax, inconsistent and very annoying.”

The Data Management blog says, “compression tools are a must for any DBA”, asserting that, “At a high level, compression software in itself can give you a vast amount of options that you simply may not be able to grasp without.”

PowerShell could be another useful tool. So believes the Scary DBA, who offers a link to an article that shows how PowerShell can help you as a DBA.

Oracle

Why do I have hundreds of child cursors when cursor_sharing set to similar in 10g? A question answered on Inside the Oracle Optimizer.

Tanel Poder has on offer some scripts for showing execution plans via plain SQL and also in Oracle 9i.

CPU Costing and the effects of multiple blocksizes - part 4 arrives at Randolf Geist’s Oracle related stuff.

On the Oracle Scratchpad, Jonathan Lewis describes “CPU used,” which demonstrates how, “‘CPU Time’ in the ‘Top N Timed Events’  . . .  [looks] very different from the ‘BUSY_TIME’ that appears in the ‘OS Statistics’ part of the [Statspack] report.”

MySQL

On High Availability MySQL, Mark Callaghan has a good reason to use inodb_file_per_table — per-table IO statistics.

As does Shlomi Noach, with his reasons to use innodb_file_per_table.

Domas Mituzas is having none of it. Stop messing with the tablespace, he writes. But his readers might still think otherwise.

Dimitri K. looks into InnoDB Dirty Pages & Log Size Impact. He begins, “ . . . seeking for the most optimal MySQL config parameters I’ve discovered a strange thing: my dirty pages percentage setting 15 was completely ignored by InnoDB during my tests; [and] once the test workload was finished it still took 30 minutes yet to flush dirty pages!”

On the MySQL Performance Blog, Peter Zaitsev demonstrates the mass killing of MySQL Connections. “There is  . . .  a way to do it just using MySQL with a few commands,” he writes.

That’s all for now. I’d love to hear from you, so please share your favourite DB blogs from the week gone by in the comments.

Till next time!

Let’s start this week, with blogs from the SQL Server world, where a number of excellent technical posts appear. Alexander Kuznetsov surprises his readers with this assertion: without ORDER BY, there is no default sort order. “Sounds trivial? Right, but different flavors of this myth still persist.  . . .  Because apparently many visitors agreed with this myth, I decided to post a repro script which demonstrates that this is simply not true.”

In their post on Read/Write deadlock, the rusano.com blog likewise was answering a question, how does a simple SELECT deadlock with an UPDATE? “Surprisingly, they can deadlock even on well tuned systems that does not do spurious table scans. The answer is very simple: when the read and the write use two distinct access paths to reach the same key and they use them in reverse order.” Examples and fixes follow.

Linchi Shea looks for an answer to this mystery—why the tempdb log keeps growing. Linchi says, “Whether it’s a user database or tempdb, when its transaction log is filled up or forced to autogrow, large long-running transactions should not be the only potential culprit for you to track down.”

The SQL Programmability & API Development Team Blog was also concerned by the matter of unexpected growth, in their case seeking to provide an answer to the question, Why did the size of my indexes expand when I rebuilt my indexes?

On a related matter, Paul S. Randal gave an example of a nasty cluster key on In recovery… Paul’s readers offers examples from their own experience of disastrous primary keys and clustered indexes.

Michelle Ufford, the SQL Fool, covers overhead in non-unique clustered indexes, giving a walk-through of scenarios in which the DBA will encounter this.

In the Oracle ’sphere, Hemant K Chitale examines 90-10 Index Block Splits and their possible causes.

Jonathan Lewis has the perfect thing to follow your Log Buffer read—a lunchtime quiz on the Oracle Scratchpad. There are lots of answers already posted, so no peaking below the fold.

Pythian’s André Araujo responds to a different test with his very elegant NoCoug SQL Challenge Entry.

Girlgeek Claudia Zeiler made problems for herself: “Playing around with my toy database I asked myself, ‘What happens if DUAL has more than 1 row?’ I found out.” Marco Gralike offers some relevant links in his comment. Read and learn.

“I’ll Gladly Pay You Tuesday for a Hamburger Today,” quotes Kerry Osborne, who was in a Wimpy frame of mind at the time. The analogy to J. Wellington Wimpy’s burger-mooching , Kerry writes, applies to, “ . . . paying the price for our bad/missing statistics.”

Here’s Laurent Schneider with a tip on how to reuse a connection in the shell.

MySQL bloggers are still very taken up with the future of their beloved DBMS in the wake of its acquisition by Oracle Corporation.

Curt Monash of DBMS2 observed, “MySQL forking heats up, but not yet to the benefit of non-GPLed storage engine vendors”.

Paul McCullagh of PrimeBase XT writes, At last we have a MySQL Foundation, its called The Open Database Alliance. “What is really most important,” Paul writes, “is that we in the community now have an entity that is going to tie our side of things together . . .  For the community it is critical that things do not split up any further and that instead our efforts are bundled. I believe the Alliance can do this for us.”

Or is it already too late? Neil McAllister of Developer World wonders if MySQL is forked beyond repair.

Not everyone had their eyes on the DBMS chess game. Vadim of the MySQL Performance Blog examined what time 18446744073709550.000 means. The answer, Vadim and his readers show, comes from a very low-level indeed.

Johan Andersson’s Cluster and HA Blog offers a thorough HOWTO on write scaling using Cluster to non-cluster replication. “There are various setups and solutions,” Johan begins, “to solve the problem of having redundant mysql masters and scaling writes on them. MySQL Cluster can be an alternative. Here is why and how.”

“When working with InnoDB,” writes Schlomi Noach, “you have two ways for managing the tablespace storage.  . . .  I will discuss the advantages and disadvantages of the two options, and will strive to convince that innodb_file_per_table is preferable.” The item is, Reasons to use innodb_file_per_table.

PostgreSQL. Just across the Rideau Canal from where I sit, PGCon 2009 is happening. Magnus Hagander gives his review of PGCon’s first day.

Andrew Dunstan attended Robert Treat’s talk on new features in 8.4, and concluded that small features can still win big.

IBM’s EMEA Information on Demand 2009 Conference takes place in June in Berlin. Vincent Burney notes that the IBM IOD conferences and sessions now have Twitter tags and speaker blogs, and he provides useful links to these and other IOD resources.

Leons Petrazickis of the DB2 Express-C Team Blog wonders, “What are you working on with DB2?” “I just created an informal round-robin forum thread to see what everyone is working on with DB2 Express-C. It’s an exercise in community participation, if you will.”

That’s all for this edition. Let us hear about your favourite DB blogs from the week gone by—please leave a comment.

Till next time!

Oracle

Let’s start with Jonathan Lewis’s report from IOUG Day 4: ” Not so much a little gem today as a little surprise and a few consequential thoughts. In a presentation on optimising star transformations the presenter pointed out that bitmap indexes are only available in Oracle Enterprise Edition.”

Here’s Doug Burns with the first of a series on Adaptive Thresholds in 10g (Metric Baselines). Doug writes, “[I really didn't want to get into another multi-part blog post, but this has grown longer than I hoped, so I'll split it up ...]”

Doug, you could have started with the second part, as Kevin Closson did: You Buy a NUMA System, Oracle Says Disable NUMA! What Gives? Part II Haven’t read Part I? Don’t worry. “Yes, in this mini-series of posts Part II will precede Part I. I’ll explain…eventually,” writes Kevin.

Richard Foote still has left Doug and Kevin in the dust, having got to Part V of his Indexes And Small Tables series.

Kerry Osborne was playing with numbers too, in his own way—pointing out some extremes in buffer cache sizes, and asking for his readers’ experiences.

John Hallas ponders autostart using the ‘W’ flag in oratab: “In 10.2.0.2 an option arrived to manage the automatic startup and shutdown of the databases.  . . .  However on playing around with these settings . . . I could not see any way that the functionality was working.” Your feedback is requested.

MySQL

George J. Trujillo Jr. wonders about Oracle SQL Developer with MySQL: “I am always asked, what GUI to you recommend with MySQL? Two of the most popular are SQLYog and Navicat for MySQL customers.  . . .  I think it is time to see how well SQL Developer works with MySQL.” Roland Bouman appears with a link to his own review of SQL Developer in this light.

On the Colin Charles Agenda appears an interview with Rohit Nadhani, founder of Webyog. And there’s Sheeri Cabral with a link to her review of Webyog.

Speaking of Sheeri . . .  What kind of colleague would I be if I failed to mention that her just-published book the MySQL Bible is here. Congratulations, Sheeri!

On code.openark.org, Shlomi Noach writes, “It seems like MySQL is unable to utilize a compound index when evaluating a plan for a query with a range condition. I’m looking for an explanation. I’ll appreciate any insight on this.” His readers respond and discuss the matter.

Matt Yonkovit, one of MySQL blogging’s two Big DBA Heads, begins a series of Sun/Intel X-25e 4 Disk Raid 10 tests. Matt begins thus: “Those who follow my blog know I love IO and I love to benchmark anything that can help overcome IO issues. One of the most exciting things out their at this point are the Intel x-25e drives. These bad boys are not only fast but relatively inexpensive. How fast are they? Let’s just do a quick bit of review here and peak at the single drive #’s from sysbench.”

Monty says that the Open Database Alliance is founded. “Monty Program Ab and Percona today launched the Open Database Alliance.  . . .  This may be one of the most important steps in the history of MySQL and MariaDB.  . . .  Here follows my initial vision of the Open Database Alliance.”

Josh Berkus of Database Soup took notice of Monty’s declaration, and approves.

Giuseppe Maxia, the Data Charmer, announces a MySQL Event in Montreal, this Monday, the 18^th of May.

PostgreSQL

From even closer to home comes a call for PgCon 2009 lightning talks, courtesy Selena Deckelmann. (PGCon itself begins here in Ottawa, Canada on May 19.)

Let’s go back to Josh Berkus for a moment. He has published a guide to using 8.4 Parallel Restore with your 8.3 or 8.2 database.

SQL Server

Martin Bell, UK SQL Server MVP started blogging this week, with (you guessed it) the first of a series on table-valued parameters in SQL Server 2008.

Denis Gobo has a couple of reasons he won’t be moving my databases to the cloud anytime soon. Six reasons for SQL Server Data Services, to be precise.

Why use stored procedures, asks Paul Nielsen. In his view as a data architect, extensibility is the key: “The data architect’s answer to why use stored procedures is that T-SQL is only language that you KNOW will last as long as the data.”

On the Journey to SQL Authority with Pinal Dave, we stop to find the last date time updated for any table.

The Scary DBA offers some PowerShell basics. Others are not so keen—Bill G.’s thoughts on SQL Server include, Why am I being forced to learn PowerShell?

There are more blogs, but no more time, so that’s all for now. Please mention your favourite blogs from this week in the comments, and get in touch with me to host an edition of Log Buffer on your own weblog.

Till next time!

MySQL

Since MySQL was surely the belle of the bloggers’ ball this week—why, everyone was talking—let’s begin with it.

Baron Schwartz started something with his post examining why MySQL might not benefit from having a mother ship. Dean Ellis of niflheim responded, arguing that everyone needs the MySQL mothership. And that got Sheeri’s Cabral’s attention—she took the middle path in her post, What If, and her readers had plenty to say.

Justin Swanhart gave news and opinion in one headline: MySQL documentation team announces docs will NOT be GPLed. Boo MySQL. Boooo, adding, “I’m now totally convinced that MySQL does not understand, and will never understand the MySQL community.” In his piece on MySQL docs freedom, Arjen Lentz wrote, “I believe this is a serious concern for the product as a whole, and hope this concern will be addressed by Sun Microsystems very soon - with action.”

Yoshinori Matsunobu’s item illuminating Linux I/O scheduler queue size and MyISAM performance attracted some comment, as did the MySQL Performance Blog’s detailed review of Tokutek storage engine.

Giuseppe Maxia, the Data Charmer, was road testing too, test-driving the Spider storage engine.

Jeremy Zawodny wants to hear your thoughts on the question, is MySQL 5.1 a compelling upgrade?

Fernando Ipar looked into SOUNDEX(), triggers, and stored procedures, beginning, “ . . . If you’re storing multiple-word strings, things get a little more complicated, since they can’t be compared by their soundex.  . . .  If at a later time, you want to search for a subpart of this phrase, there’s no way for you to do this. Well, at least not directly . . . ”

On the zillablog, Robert Treat was taking a stab at 50 things to know before migrating MySQL to Oracle, and making it all the way to 29.

Oracle

Some conference stuff. Jason Arneil posts the UKOUG 2009 Annual Conference Call for Papers. The 3rd Planboard DBA Symposium was announced by Frits Hoogland.

Jonathan Lewis delivers his philosophy (the first part of it, at least). Christian Antognini says, “AMEN”.

Jared Still has updated and published his script for querying v$lock.

John Hallas offers an account of his experiences with DBMS_DATAPUMP using the API.

George Trujillo writes, “It is always important to make sure you are maintaining your skill set and marketability as an Oracle professional. In a down economy it is even more so for a DBA. So my question to you is, do you try to scale vertically or horizontally?”

SQL Server

At the Home of the Scary DBA appeared something along similar lines, Database Screening Questions, picking up a thread from Brent Ozar and the SQL Batman on newbie DBA interviewing.

Bart Duncan showed how sometimes the simplest solution isn’t the best solution, specifically vis-a-vis the all-in-one search query.

DELETE FROM Where? asks Steve Kass. “For years, SQL Server has supported a (second) FROM clause in UPDATE and DELETE statements. Its behavior isn’t always deterministic, a fact Microsoft points out in the documentation.  . . .  Today, someone was surprised by the basic semantics of DELETE .. FROM. This probably happens a lot . . . ”

MS’s Bob Ward, for his part, asks, Why Should I Use Extended Events in SQL Server 2008? “You may or may not have heard of a new diagnostic technology in SQL Server 2008 called Extended Events (XEvent). I thought I would post an example of why this technology can do things nothing else we have can when you deploy SQL Server 2008.”

Paul S. Randal brings news of a performance bug: NOLOCK scans involving off-row LOB data. “Bottom line is that if you’re doing NOLOCK scans of tables involving LOB data, the performance might suck.”

Tim Ford, SQLAgentMan, wondered what it would be like if SQL Server was a musician. “SQL Server Elvis Edition - does not scale out well. Dumps are not graceful.”

Oh, speaking of which, here’s Kevin Kline reporting that Microsoft marketing throws SQL Server under the bus after some trouble with a Windows 7 Beta release.

IBM DBMSs

On the DB2PORTAL Blog, Craig Mullins offers his approaches to access path management… or The Five R’s.

Kate Dawson wants to know, are you going to IDUG?, offering links and details.

The Informix Zone has a dispatch from the IIUG Conference 2009, complete with lots of links and pictures.

Jacques Roy provides his answers to a question you might find yourself asking—Why Informix?

PostgreSQL

Andrew Dunstan announces the birth of PostgreSQL Experts Inc., a company “ . . . aimed at providing full service to PostgreSQL users, from setup to tuning to administration to application development. We have some people who are pretty well known in the PostgreSQL community, including Josh Berkus, our CEO, and David Wheeler and David Fetter, as well as your humble blogger . . . ”. Congratulations, guys, have a cigar!

Andrew also examines materialised views for large joins. He writes, “Postgres doesn’t have builtin support for materialised views (yet). But they are pretty easy to set up.”

Firebird

It’s time to nominate Firebird for CCA 2009, SourceForge’s Community Choice Awards, says Firebird News. Firebird is nominated for Best Project, Best Tool or Utility for Developers, and Best Project for the Enterprise.

On Free Database: The Relational Databases Blog appears an embedded Firebird database overview. It begins, “I was looking for a small and powerful database in order to fulfill the requirements of my last project. Because the database will be running locally I took the decision to use an embedded database. After a few searches over the Internet and some embedded database comparison reviews, I found Firebird which is actually a powerful but unknown (yet) relational database system.”

On Compas Pascal, Lars Dybdahl makes some observations on the real-life latency of a Firebird server.

Before we say goodbye, let’s go back to MySQL. Amidst all of the chatter and controversy, Gary Pendergast wishes to remind us that MySQL is People! And to illustrate that point, he throws himself from an airplane. The connection isn’t too clear to me, but I do hope MySQL has a parachute that works just as well.

As always, I invite you to mention your favourite DB blogs from this week in the comments. Until next time!

After the shock of the Oracle takeover the MySQL community is full of hope. Mark Callaghan has written about the new storage engines for MySQL and also suggestions for what the MySQL community could be doing while they wait to hear what Oracle has planned.

Kaj Arno has looked to the future and he thinks he has found some answers.

With the media constantly bombarding us about economic meltdown and pandemics, its nice to read someone who sees something positive. Selena Deckelman sees hope in the world after a conversation with the Paul Vallée.

But its not just the MySQL world that is looking forward—DB2 users are too, with the imminent release of versions 9.5 thru to 9.7.

The always readable Jonathan Lewis celebrates his millionth visitor by comparing himself to Susan Boyle. For this milestone, Jonathan deserves a kiss, too, don’t you agree?

Talking about always readable, Steve Feurerstein has an interview with one of the best PL/SQL developers he knows. Certainly one of the best I have ever read.

Not to be outshone by Larry, Bill and his pals at Microsoft have made a few announcements this week. Aaron Bertrand is one of many to report that locked pages are now available as a standard edition feature on SQL Server.

Michelle Ufford give us some tips on how to find and deal with missing indexes.
Obviously, Michelle and Ward Pond have too much time on their hands, but I am not sure even Shakespeare would say “play on” to this.

Steve Kass has some good advice on using @@rowcount in MERGE triggers. “The value of @@rowcount inside a trigger could be unexpected, if the triggering statement was MERGE … but fortunately there’s a simple workaround.”

Everyone has their top 5 best practices. If your 5 differ completely from everyone else, then either you’re a genius or they stink. More likely to be the latter rather than the former. Tim Ford gives us his Top 5 this week. How many are on yours?

Robert Hodges takes a different view of the Oracle-MySQL marriage and asks, where are the 50 things you need to know about migrating from MySQL to Oracle.

Antonio Cangiano has a useful blog this week for all you macs out there on how to install DB2 onto the mac OS X Leopard.

It is spring time, and at this time of the year our minds turn to cleaning. Troy Coleman, therefore, has a timely article on when to clean out your obsolete packages.

Craig Mullins advises on some basic buffering and memory guidelines for DB2: “The better memory is allocated … the better DB2 will perform.”

I hope you’ve enjoyed this edition of Log Buffer, and I invite you to share your favourite blogs from the week in the comments. I’ll see you again soon!

So . . .  Anything happen while I was away?

Okay, so I heard the big news. And just in case you haven’t, here it is from Sheeri Cabral: Oracle Buys Sun. This is a sea-change in the hi-tech world, and the DB part of it will also get rocked, Sun being the home of MySQL. There’s lots of comment in Sheeri’s post, and indeed, all over the database blogging world. I will try here to cover the best of it.

Oracle + Sun + MySQL

First, Monty Says: to be (free) or not to be (free), that is the question. He projects three possible ways Oracle could treat MySQL, and extends a hand to what he expects will be yet more disenchanted MySQL employees.

On The Open Road, Matt Asay asks, Oracle can help Sun, but will it lose MySQL?: “Given the fracturing we’ve already seen with MySQL . . . I suspect that we may be in for several more forks of the MySQL code base.  . . .  So here’s a thought: could Red Hat fork MySQL, hire some key developers, and effectively assume the mantle of MySQL leadership?”

Pythian’s Paul Vallée obligingly gathered links to Curt Monash’s analyses of the Sun/Oracle deal. Those are very worth reading.

In his post MySQL, Sun and Oracle, Kristian Köhntopp bases his predictions on this premise: “MySQL has been instrumental in building a completely new database market. 12 years ago most people were . . . storing data in flat files. SQL knowledge was expert knowledge, and if you knew SQL you were either out of academia or have been on the career and certification-programme of some vendor.”

Mark Schoonover offers his thoughts on Oracle’s Purchase of Sun: “Who could be impacted by Oracle’s purchase? That huge computer company in Redmond. For years, their database team has had access to the operating system source code.  . . .  Oracle not only gains the source code to Solaris, but also their hardware too. No company in my 22 years in IT has had access to everything - hardware, operating system and the database. It’s going to be a wild ride.”

On the Oracle side, Glenn Fawcett takes a pragmatic point of view: “Could you imagine… ‘Dtrace probes for Oracle?’ How cool would that be?”

In his post, So Oracle buys Sun, Andrew Clarke says, “The notion of Oracle as a hardware vendor is an intriguing one. Oracle will be able to offer appliances such as Exadata without the trouble (and loss of potential revenue) incurred by partnering with a hardware vendor. The flip side is that hardware vendors may be less happy to accommodate Oracle on their boxes.”

From PostgreSQL, Peter Eisentraut writes, “Now with MySQL actually owned by Oracle, this makes PostgreSQL the primary alternative.  . . .  I don’t expect that MySQL will be “killed” either.  . . .  Much of the MySQL momentum already lies outside of Sun anyway, in the hands of Percona, Open Query, the Monty Program, Drizzle, and others, so killing MySQL is already impossible for a single company. Which is probably a good situation for the extended open-source database community.”

Now, I’m not sure exactly what Christopher Powers means by this image from his post Whither MySQL?, but it certainly captures the portent of the moment.

MySQL

Okay, enough of that. It was also, coincidentally, the week of MySQL Conference. Shlomi Noach took home the Community Member of the Year Award. Congratulations, Shlomi.

Colin Charles observes that it’s a storage engine world, after all, recounting the storage engine-related news from the conference.

Jeremy Cole related why he was skipping the MySQL Conference and Expo.

In the wake of the announcement of MySQL 5.4 at the conference, Ronald Bradford noted a change in the MySQL Binary distributions. Hide-and-SQL tried to answer the question, Why 5.4?

SQL Server

On In Recovery…, Paul S. Randal looked inside the storage engine: more on the circular nature of the log.

Alexander Kuznetsov gave part one of avoiding infinite loops by Alexander Kuznetsov gave part one of avoiding infinite loops by . . .  Mm, guess I’d better go read that.

Here’s an important question: Is it Time for a Professional Code of Ethics for DBAs?, discussed by Kevin Kline and his readers.

syscomments had one too: What’s the deal with SQL Server 2008 implementation?. “I was talking with a Microsoft representative at PASS and he asked me about our SQL Server 2008 implementation plan.  . . .  ‘I don’t have one.’”

Michelle Ufford, SQL Fool, explains her favourite 2008 feature—Filtered Indexes: What You Need To Know.

On Journey to SQL Authority, Pinal Dave offers an excellent introduction to JOINs.

PostgreSQL

Jignesh Shah published a HOWTO on trying Postgres 8.4 Beta1 using OpenSolaris Appliance for VirtualBox.

Bruce Momjian has setup a poll for people to vote on the anticipated release date of Postgres 8.4 final.

IBM DBMSs

On An Expert’s Guide to DB2 Technology, Chris Eaton writes, DB2 9.7 is Announced by IBM - I think it has something for everyone.

On his Informix technoology blog, Fernando Nunes has published a very thorough overview of Informix authentication and connections.

Oracle

Chen Shapira is back with a gazetteer for those of us who may have got lost following the NoCoug SQL Challenge.

Frank van Bortel has three excellent posts on special characters: “Special” Characters - part I; “Special” Characters - part II; and “Special” Characters - part III.

On The Dutch Prutser’s Blog, Harald van Breederode demonstrates flushing a cursor out of the library cache.

Kerry Osborne wonders about Hidden SQL - why can’t I find my SQL Text?, beginning, “A very frequently executed statement on a database was generating some waits on ‘SQL*Net more data from client’. ASH shows the statement, as does the V$SESSION view, but the statement never shows up in the V$SQL view nor in the AWR tables.”

Dion Cho responded to that with his item on LOB, sql_id and LCO.

And that is all. Oracle, Sun—no more big news for a while, if you please.

See you in a week’s time.