Gokhan Atil's Technology Blog

How To Find Storage Occupied by Each Internal Stage in Snowflake?

The account usage view has two views related to stages: STAGES and STAGE_STORAGE_USAGE_HISTORY. The STAGES view helps list all the stages defined in your account but does not show how much storage each stage consumes. The STAGE_STORAGE_USAGE_HISTORY view shows the total usage of all stages but doesn’t show detailed use.

I wrote the following script to list the internal stages (and their occupied storage) in all available databases:

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Amazon QLDB and the Missing Command Line Client

Amazon Quantum Ledger Database is a fully managed ledger database that tracks all changes in user data and maintains a verifiable history of changes over time. It was announced at AWS re:Invent 2018 and is now available in five AWS regions: US East (N. Virginia), US East (Ohio), US West (Oregon), Europe (Ireland), and Asia Pacific (Tokyo).

You may ask why you would like to use QLDB (a ledger database) instead of your traditional database solution. We all know that it’s possible to create history tables for our fact tables and keep them up to date using triggers, stored procedures, or even with our application code (by writing changes of the main table to its history table). You can also say that your database has write-ahead/redo logs, so it’s possible to track and verify the changes in all your data as long as you keep them in your archive. On the other hand, this will create an extra workload and complexity for the database administrator and the application developer. At the same time, it does not guarantee that the data was intact and reliable. What if your DBA directly modifies the data and history table after disabling the triggers and altering the archived logs? You may say it’s too hard, but you know that it’s technically possible. In a legal dispute or a security compliance investigation, this might be enough to question the integrity of the data.


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Sample AWS Lambda Function to Monitor Oracle Databases

I wrote a simple AWS Lambda function to demonstrate how to connect an Oracle database, gather the tablespace usage information, and send these metrics to CloudWatch. First, I wrote this lambda function in Python, and then I had to re-write it in Java. As you may know, you need to use the cx_oracle module to connect Oracle Databases with Python. This extension module requires some libraries shipped by Oracle Database Client (oh God!). It’s a little bit tricky to pack it for the AWS Lambda.

Here’s the main class which a Lambda function can use:

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How to Build A Cassandra Cluster On Docker?

In this blog post, I’ll show how to build a three-node Cassandra cluster on Docker for testing. I’ll use official Cassandra images instead of creating my images, so all processes will take only a few minutes (depending on your network connection). I assume you have Docker installed on your PC, have an internet connection (I was born in 1976, so it’s normal for me to ask this kind of question), and have at least 8 GB RAM. First, we need to assign about 5 GB RAM to Docker (in case it has less RAM) because each node will require 1.5+ GB RAM to work properly.

Docker Memory

Open the docker preferences, click the advanced tab, set the memory to 5 GB or more, and click “apply and restart” docker service. Launch a terminal window, and run the “docker pull cassandra” command to fetch the latest official Cassandra image.

I’ll use cas1, cas2, cas3 as the node names, and the name of my Cassandra cluster will be “MyCluster” (a very creative and unique name). I’ll also configure cas1 and cas2 like they are placed in datacenter1 and cas3 like it’s placed in datacenter2. So we’ll have three nodes, two of them in datacenter1 and one in datacenter2 (to test Cassandra’s multi-DC replication support). For multi-DC support, my Cassandra nodes will use “GossipingPropertyFileSnitch”. This extra information can be passed to docker containers using environment variables (with -e parameter).

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