This Log Buffer edition covers Oracle, SQL Server and MySQL blog posts with a touch of Cloud.
Provisioning EBS on Oracle Cloud: Latest Enhancements
ORA-54002 when trying to create Virtual Column using REGEXP_REPLACE on Oracle 12cR2
Business rules, common sense and query performance
Problem with V$RECOVERY_AREA_USAGE view and FRA space not being reclaimed
Updated SQLcl: 2 New Commands, Bug Fixes, and 12cR2 Oh My!
This Log Buffer Edition searches through various blogs of Oracle, SQL Server and MySQL and picks a few contemporary ones.
Comma separated search and search with check-boxes in Oracle APEX
Once you have defined your users for your Express Cloud Service, all users with the role of Database Developer or higher can access the database Service Console.
Big Data Lite 4.7.0 is now available on OTN!
Data Pump or Data Pain Part02 – tablespace/user
Monday Spotlight: It’s About Security – Oracle Exadata SL6
OGG Custom Adapters: How to include a unique identifier for every record in custom adapter?
I published my 2014 presentation “Making MySQL highly available using Oracle Grid Infrastructure” in Slideshare. You can view it here:
At last night's WWCode Cincinnati panel, I recommended that developers talk to their DBA about what advanced capabilities their RDBMS can offer, so that they don't end up reimplementing functionality in the app that are already available (better and more efficiently) in the database itself. Devs can waste a lot of effort by thinking of databases as dumb, inert data boxes.
I was asked an excellent question: "Where can a dev quickly familiarize herself with (more...)
I last wrote about Couchbase in November, 2012, around the time of Couchbase 2.0. One of the many new features I mentioned then was secondary indexing. Ravi Mayuram just checked in to tell me about Couchbase 4.0. One of the important new features he mentioned was what I think he said was Couchbase’s “first version” of secondary indexing. Obviously, I’m confused.
Now that you’re duly warned, let me remind you of aspects of (more...)
In MySql world it can cause confusion or possible problems with synchronisation in Galera cluster configuration.
Let’s check some examples.
I have MySQL database with datadir=/data in configuration file. I have deleted lost+found directory and restarted MySQL service.
When I list my databases this is result:
Using sysbench to performance test AWS RDS MySQL hardware is an easy three step operation.
Sysbench creates synthetic tests and they are done on a 1 mil row 'sbtest' table that sysbench creates in the MySQL database you indicate. The test doesn't intrude with your database schema, and it doesn't use your data, so it is quite safe. The test is an OLTP test trying to simulate event operations in the database as it (more...)
In this post I will talk about how to measure replication lag and check/fix replication inconsistencies with this tools:
I am using environment from previous blog post.
Master-Master replication with MariaDB 10.0.16 database on Debian 7.
Install Percona Toolkit on both nodes:
$ sudo wget percona.com/get/percona-toolkit.deb
Another method is to set up replication in both directions called master-master replication. But you must be aware that this setup brings some potential issues as data changes are happening on (more...)
ERROR 1205 (HY000) : Lock wait timeout exceeded; try restarting transaction
You get the error because your allocated time to hold a DML lock in a transaction exceeds the set limit. Usually the default limit to hold a DML row lock, set by innodb_lock_wait_timeout db parameter, is 50 seconds. If your transaction doesn't commit/rollback within 50 seconds (more...)
I’m taking a few weeks defocused from work, as a kind of grandpaternity leave. That said, the venue for my Dances of Infant Calming is a small-but-nice apartment in San Francisco, so a certain amount of thinking about tech industries is inevitable. I even found time last Tuesday to meet or speak with my clients at WibiData, MemSQL, Cloudera, Citus Data, and MongoDB. And thus:
1. I’ve been sloppy in my terminology around “geo-distribution”, in (more...)
I've never had a tool I really liked that would extract a chunk of a large production database for testing purposes while respecting the database's foreign keys. This past week I finally got to write one: rdbms-subsetter.
rdbms-subsetter postgresql://user:passwd@host/source_db postgresql://user:passwd@host/excerpted_db 0.001
Getting it to respect referential integrity "upward" - guaranteeing every needed parent record would be included for each child row - took less than a day. Trying to get it to also guarantee (more...)
A Pandas DataFrame has a nice to_sql(table_name, sqlalchemy_engine) method that saves itself to a database.
The only trouble is that coming up with the SQLAlchemy Engine object is a little bit of a pain, and if you're using the IPython %sql magic, your %sql session already has an SQLAlchemy engine anyway. So I created a bogus
PERSIST pseudo-SQL command that simply calls
to_sql with the open database connection:
%sql PERSIST mydataframe
The result is (more...)
PyOhio gave my lightning talk on ddlgenerator a warm reception, and Brandon Lorenz got me thinking, and PyOhio sprints filled my with py-drenaline, and now ddlgenerator can inspect your data and spit out SQLAlchemy model definitions for you:
$ cat merovingians.yaml
name: Clovis I
name: Childebert I
$ ddlgenerator --inserts sqlalchemy merovingians.yaml
from sqlalchemy import create_engine, Column, Integer, Table, Unicode
For my example, (more...)
For my newest ipython-sql trick, I needed to compare some queries run across different databases. How hard would it be to get side-by-side results into tidy IPython Notebook output?
Not hard at all, it turns out, if you're willing to violate basic principles of human decency.
That's an itty-bitty image, (more...)
When to consider sharding a MySQL database
Why should you not just design your applications from the start to account for data sharding? Sharding a database, that is horizontally partitioning tables among multiple databases, creates an added level of complexity that is not desirable in an application. However, there are times when sharding is required to maintain acceptable performance. So when is the right time to shard your database?
When to consider sharding a MySQL database Why should you not just design your applications from the start to account for data sharding? Sharding a database, that is horizontally partitioning tables among multiple databases, creates an added level of complexity that is not desirable in an application. However, there are times when sharding is […] -->