Author Archives: tobias
SQL Scratch
These are just scratches/notes for my work with Prestashop select id_product, reference from ps_product where reference like ‘9254050’ limit 10; Uppercase first letter only on string, and lowercase the others (remove any spaces infront or at the end)select name, concat(upper(left(name,1)),lower(substring(name,2,length(name)))) … Continue reading
Functions as Arguments Java vs Scala, Game Set Match Scala Wins!
This is how you would create a function that takes a function as argument in Java The Function<A,B> myFunc = num -> “Value = ” + num;Here :A = the type of the first argument, in this example an intergerB … Continue reading
Apache Cassandra Secondary Indices
How are Secondary Indices really stored ? This is based on the article from Datastax found here; https://www.datastax.com/blog/2016/04/cassandra-native-secondary-index-deep-dive Let’s just create a simple table
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CREATE TABLE customer ( id int PRIMARY KEY, city text, name text ) |
Or visualized as a table : Column Type Key id int Primary Key city text name … Continue reading
Print stacktraces for all threads on shutdown
If your microservice stops responding from time to time, and they only way out is to kill it with SIGINT or SIGTERM then adding a shutdown hook might be the way to go. Do note that this will not work … Continue reading
Apache Zeppelin, with Spark and Cassandra, the perfect tool
Zeppelin has become one of my favourite tools in my toolbox. I am heavily designing stuff for Cassandra and in Scala, and even though I love Cassandra there are times when things just gets so complicated with the CQL command … Continue reading
Remove the cardo-updater agent from OSX
I have the intercom from Cardo Systems, and it is really good BUT when I updated the firmware some time agoe, it decided to install some software that takes port 8080, which is one of those really common ports used … Continue reading
SQL LIKE operation in Cassandra, is possible in v3.4+
For a long time it has not been possible to do a SELECT * FROM table WHERE firstname like ‘t%’; in Cassandra like you could in eg.. MySQL or any other Relation Database for that matter. In Cassandra v3.4 this … Continue reading
UDF/User Defined Functions in Cassandra 3.x
I was just playing around with Cassandra WRITETIME and thought it was somewhat difficult to figure out the date / timestamp of a number like this (microseconds since EPOC) 1470645914253000. So in my example it looked like this
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cqlsh:bth> select id, writetime(dateofbirth) from bth.employee; id | writetime(dateofbirth) ----+------------------------ 1 | 1470645914253000 2 | 1470645977177000 7 | 1470948508799001 3 | 1470645977178000 (4 rows) cqlsh:bth> |
So … Continue reading
Cassandra set the writetime explicitly with a PreparedStatement
This is a quick one, I wanted to set the writetime of a row explicitly when I populate the database for testing purposes. We use the writetime of a column to filter them out. It required some looking around to … Continue reading
Apache SPARK and Cassandra and SQL
This is a short intro to start using Apache SPARK with Cassandra, running SQL on the Cassandra tables. Note that I am not running a SPARK cluster, I am running “local”, to me this is really convenient, not having to … Continue reading