Log Buffer #152: A Carnival of the Vanities for DBAs
Jul 3, 2009 / By David Edwards
Welcome to the 152nd edition of Log Buffer, the weekly review of database blogs.
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.”
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.”
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.
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.”
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 . . .
(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!
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