The look of : transaction deadlock due to missing foreign key index

This about transaction deadlocks resulting from an index missing on foreign key colum(s). Actually, the post will not dive into the odds resulting from this failure but show how to detect this dedicated reason for an “ORA-00060: deadlock detected while waiting for resource” message. In particular, what to look out for in the trace file and how to find the table objects (instead of rows) being deadlocked against each other. The best resource on the web tackling this subject is of course (Reading deadlock trace files) from Tom Kyte, which also guided me along the way of a “no row deadlock”, see below.
Ok, on first place, some tool, Enterprise Manager for example, or whatever will notify you about entries in the alert.log, reading roughly the like as “Sun May 29 02:51:07 2016 ORA-00060: Deadlock detected. More info in file H:\ORACLE\diag\rdbms\got\got\trace\got_ora_4536.trc“. Inspecting the trace file, you should focus your attention on the first 70 lines, in most cases neglegting the trailing process information dumps. I got this, anything noteworthy will be highlighted and discussed below:


Oracle database 11g administrator certified professional finally

ocp_odb11gadmin_clr Last thursday. Glad I’ve managed to get this completed aside every day work now. Took the Oracle Database 11g: New Features for Administrators 1Z0-050 upgrade path (Oracle Database 11g – Certification Path). Weird, the exam comprises so many topics that are really expensive in terms of (additional) enterprise edition options to be licenced for operation set up (Oracle Technology Global Price List).


Using the DataImportHandler XPathEntityProcessor on a Database Resultset Column

The Solr documentation for XPathEntityProcessor introduces a spezialization subtype of EntityProcessor that is primarily depicted to process data (to be) imported from xml/http-datasources (for example, Usage with XML/HTTP Datasource). However, using XPathEntityProcessor on a FieldReaderDataSource instead on the original URLDataSource or !HttpDataSource (search for FieldReaderDataSource in Uploading Structured Data Store Data with the Data Import Handler) enables reading xml instances contained in columns delivered from database requests through SqlEntityProcessor.
Bewildered out of words and meanings…? Don’t worry, the following will give you a living example of how to craft the xml from an Oracle database easily and what to do on the Solr side to map the information datums into indexing fields. To me, this is really a nice example of how to employ xml in a true sense of a defined (well-forming, encoding) data exchange layer, hiding most if not all of the implementation details of xml processing on the database and on the search-engine. Note however, that this great time-to-market, through xml processing technically, always comes at a certain extra cost such that the xml-instances shall not become to large for this solution pattern. I will also use xml attributes for small size values instead of tags in the xml generation as one step of optimization.


Log-dedicated loop device throughput and time overhead on btrfs 4.x

This is again about real world numbers (which I like so much for being authentic ;-). The context being the throughput and time overhead of a loop device, as a poor or late man’s replacement for a real disk partition, jep I know, on copy-on-write filesystem btrfs, exclusively dedicated for logging, that is appending over and over. Why? The loop device may overflow with data without affecting the underlying filesystem, see Btrfs subvolume quota still in its infancy with btrfs version 4.2.2 for more why’s and what I tried to get btrfs subvolume with quota to work. By the way, about that though, see debian org Btrfs for a down-to-earth assessment of btrfs to date, even uttering a recommendation from what version number (4.4) to start off at the earliest near production. Anyway, what follows, adapts a test setup as in Performance of loopback filesystems, prime credits go there, and expands the layout somewhat for the btrfs C or nodatacow flag. Here we go.

Have this baseline, if you like, test on the raw iron. Well, its not raw iron really, its vmware and tons of storage below, and the shown performance is terrible I know and I only take one testset of bs / count but that won’t matter. There’s something to start off.

mkdir /tmp/loop0
dd if=/dev/zero bs=1M of=/tmp/loop0/file oflag=sync count=1000
1048576000 bytes (1.0 GB) copied, 8.9605 s, 117 MB/s
1048576000 bytes (1.0 GB) copied, 6.52867 s, 161 MB/s
1048576000 bytes (1.0 GB) copied, 5.35716 s, 196 MB/s
1048576000 bytes (1.0 GB) copied, 5.48745 s, 191 MB/s
1048576000 bytes (1.0 GB) copied, 5.14736 s, 204 MB/s