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Day: July 1, 2022

Locking Mechanisms in Apache Hive

Shobika Selvaraj documents lock types in Apache Hive and what commands acquire which types:

In the Shared lock there are two types one is Shared_read and Shared_write. Shared_read means anyother shared_read and shared_write query can run at a time. Shared_write lock which means any other shared_read can be performed but no shared_write lock can acquire at that time.

In Exclusive locks no shared_read or shared_write can perform at the same time.

There are three types of lock state:

   (a) Acquired – transaction initiator hold the lock
   (b) Waiting – transaction initiator is waiting for the lock
   (c) Aborted – the lock has timed out but has not yet been cleaned

I was a bit surprised about inserts being shared read but that’s not a typo in the table—Shobika brings receipts.

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Stacked Bar Charts

Alex Velez takes us through stacked bar charts:

A few years ago, we posted a question on this blog that is as relevant today as it was years ago: “Is there a good use case for a stacked bar chart?” 

Stacked bars are everywhere; you’ve likely seen them in a recent report, a dashboard, or in the media. Despite their prevalence, they are commonly both misused and misunderstood. In this guide, we’ll aim to rectify these mishaps by sharing examples, clarifying when you should (and shouldn’t) use a stacked bar chart, and discussing best practices for stacking bars. 

Read on for plenty of good advice around when to use stacked (either regular stacked bar charts or 100% stacked), horizontal vs vertical, and how to format them when it does make sense to drop one in.

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Date-Time Binning in Cosmos DB

Hasan Savran bins some data:

I wrote about the Date_Bucket() function in SQL Server a couple weeks ago. Azure Cosmos DB team announced the same functionality with a different name DateTimeBin() function. It works exactly the same with the Date_Bucket() function of SQL Server.

     Cosmos DB version of the function has the same number of parameters. The order is different. All the datatime parameters must be in ISO 8601 format (YYYY-MM-DDThh:mm:ss.fffffffZ)

Read on to see how it works.

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The Print Operator in KQL

Robert Cain continues a series on KQL:

In this post we’ll cover the print operator. This Kusto operator is primarly used as a development tool, to test calculations.

The samples in this post will be run inside the LogAnalytics demo site found at This demo site has been provided by Microsoft and can be used to learn the Kusto Query Language at no cost to you.

Importantly, this is an operator and not a statement. This is in contrast to languages like T-SQL.

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Power BI as an Enterprise Data Warehouse

James Serra follows Betteridge’s Law of Headlines:

With Power BI continuing to get many great new features, including the latest in Datamarts (see my blog Power BI Datamarts), I’m starting to hear customers ask “Can I just build my entire enterprise data warehouse solution in Power BI”? In other words, can I just use Power BI and all its built-in features instead of using Azure Data Lake Gen2, Azure Data Factory (ADF), Azure Synapse, Databricks, etc? The short answer is “No”.

Read on to understand why Power BI shouldn’t be your data warehouse.

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When Parameter Sensitive Plan Optimization Works

Erik Darling ends on a high note:

I’ve used this proc as an example in the past. It’s a great parameter sniffing demo.

Why is it great? Because there’s exactly one value in the Posts table that causes an issue. It causes that issue because someone hated the idea of normalization.

The better thing to do here would be to have separate tables for questions and answers. Because we don’t have those, we end up with a weird scnenario.

Read on for an example of PSP at its best.

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