I was working on a problem in UVA online judge where I needed to do a simple data addition. However, the catch was year can go beyond 9999 (which is the limit in python). Below code is the python solution for this problem. I simply divided the date-delta with (1200 years, i.e. 438291 days) and added it separately after the computation. If you have unclear areas, let me know in the comments.Read More
“Automating physical database design has remained a long-term interest in database research due to substantial performance gains afforded by optimised structures. Despite significant progress, a majority of today’s commercial solutions are highly manual, requiring offline invocation by database administrators (DBAs) who are expected to identify and supply representative training workloads. Unfortunately, the latest advancements like query stores provide only limited support for dynamic environments. This status quo is untenable: identifying representative static workloads is no longer realistic; and physical design tools remain susceptible to the query optimiser’s cost misestimates (stemming from unrealistic assumptions such as attribute value independence and uniformity of data distribution). We propose a self-driving approach to online index selection that eschews the DBA and query optimiser, and instead learns the benefits of viable structures through strategic exploration and direct performance observation. We view the problem as one of sequential decision making under uncertainty, specifically within the bandit learning setting. Multi-armed bandits balance exploration and exploitation to provably guarantee average performance that converges to a fixed policy that is optimal with perfect hindsight. Our comprehensive empirical results demonstrate up to 75% speed-up on shifting and ad-hoc workloads and 28% speed-up on static workloads compared against a state-of-the-art commercial tuning tool.” 
 Full Paper: https://arxiv.org/abs/2010.09208
There aren’t many benchmarks which allow you to test your systems against a hybrid OLTP and OLAP workloads. CH-BenCHmark fills that gap by combining TPC-C and TPC-H. You can download the source from the linked site or you can use something like OLTPBench (a collection of benchmarks). However, the TPC-H modified queries are not written for SQL server. In this article, I will add the modified CH-BenCHmark OLAP queries for SQL Server.Read More
If you are trying to visualize a nice graph with NetworkX, you should be exhausted by now. After all, NetworkX only provides basic functionality for graph visualization. The main goal of NetworkX is to enable graph analysis. For everything other than basic visualization, it’s advisable to use a separate specialized library. In my case, I choose Graphviz. It’s simplistic to get an attractive visualization of a NetworkX graph with Graphviz. I’m taking a gradual start, but you may skip to “NetworkX with Graphviz” directly.Read More
This article demonstrates the physical design of a multi-column non-clustered index with include-columns. Many examples on the internet only demonstrate the most simple version of an index with a single column. This article gives a proper view of an index with multiple columns through a simple example. Furthermore, you can see how the include-columns are stored, only at the leaf level of the tree.
Here we use a simple table ‘People’ with 6 columns (ID, First Name, Last Name, Age, Sex, Address). We assume we already have a clustered index created on the ID column (it will be almost no difference if there is no clustered index as well, explained at the end). Now we are going to create the non-clustered index as defined below.
CREATE NONCLUSTERED INDEX IX_NAME ON People
INCLUDE (Age, Sex)
Below diagram shows the structure of this non-clustered index.Read More
This is a new project, I’m working on from early last year. The motivation behind this project is to build a programing language that allows users to analyze private data without exposing sensitive information. Many data analysis languages (R, Python, MATLAB etc.) in the current market assume direct access to data. PRIVATE, on the other hand, performs a privacy calculation that will make sure only non-sensitive information is released to the user.
This is the tutorial series by Simon Dennis, Founder of PRIVATE
- The Design Of Private: A Privacy-Preserving Probabilistic Language
- An Introduction To The Private Language
- Bayesian Estimation With Private Data
- Bayesian Inference With Private Data
- Plotting In Private
Contribute to PRIVATE: Git-hub
Most people got huge water bills after some time due to COVID-19. I wanted to double-check the calculation because the amount was somewhat big. Unlucky I didn’t find any online calculator that get the job done (there was a one in waterboard, but it has a maximum limit of 60 days). So I went with the default option, Excel. I thought of sharing the excel workbook I used as It might be helpful to others. I really don’t know how the VAT calculation is done, so I used 8%.Read More
I recently had to change my car battery. This is after running 4.5 years with my original battery. I replaced the original with an Amaron battery for 13000 rupees (checked the images at the end). I thought someone might find this information helpful.Read More
In times of the recent tragic Easter attacks and the insurgency in our home country Sri Lanka, The Sri Lankan Graduates’ Society, The University of Melbourne, organized a silent candlelight vigil in paying respect to the lives lost and to commemorate the much-needed unity among us to walk through these difficult times together.
Recently I wanted to run the JOB benchmark for an experiment. This benchmark uses an IMDB dataset, published in 2013. Initially, I had some trouble running the benchmark as it was designed for a PostgreSQL database. And the dataset was created in a UNIX system which can create issues when used in a Windows system. So I decided to share the exact steps you need to take to take in order to create a Microsoft SQL Server database with IMDB dataset. All the scripts used in the project can be found in this Git repo.Read More