A Deep Dive in How Slow SELECT * is

Hussein Nasser May 2, 2023
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Hussein Nasser

@hnasr

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Join me as we discuss various software engineering topics with examples and add fun elements to them. We always try to learn by example here in this educational Youtube channel which we believe is the right way to learn. I love Software engineering (especially the backend) and I strive to be a better software engineer every day. Join me on this journey and let us learn together. All opinions, suggestions, and tips I provide in all of this channel's content are my own. Information provided is for educational purposes only. Consider becoming a member to support the channel https://www.youtube.com/channel/UC_ML5xP23TOWKUcc-oAE_Eg/join Check out my courses https://courses.husseinnasser.com Stay awesome! Hussein Nasser, http://www.husseinnasser.com Feel free to shoot me an email [email protected] twitter: @hnasr

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Fundamentals of Database Engineering udemy course (link redirects to udemy with coupon) https://database.husseinnasser.com In a row-store database engine, rows are stored in units called pages. Each page has a fixed header and contains multiple rows, with each row having a record header followed by its respective columns. When the database fetches a page and places it in the shared buffer pool, we gain access to all rows and columns within that page. So, the question arises: if we have all the columns readily available in memory, why would SELECT * be slow and costly? Is it really as slow as people claim it to be? And if so why is it so? In this post, we will explore these questions and more. 0:00 Intro 1:49 Database Page Layout 5:00 How SELECT Works 10:49 No Index-Only Scans 18:00 Deserialization Cost 21:00 Not All Columns are Inline 28:00 Network Cost 36:00 Client Deserialization https://medium.com/@hnasr/how-slow-is-select-8d4308ca1f0c Fundamentals of Backend Engineering Design patterns udemy course (link redirects to udemy with coupon) https://backend.husseinnasser.com Fundamentals of Networking for Effective Backends udemy course (link redirects to udemy with coupon) https://network.husseinnasser.com Follow me on Medium https://medium.com/@hnasr/membership Introduction to NGINX (link redirects to udemy with coupon) https://nginx.husseinnasser.com Python on the Backend (link redirects to udemy with coupon) https://python.husseinnasser.com Become a Member on YouTube https://www.youtube.com/channel/UC_ML5xP23TOWKUcc-oAE_Eg/join Buy me a coffee if you liked this https://www.buymeacoffee.com/hnasr Arabic Software Engineering Channel https://www.youtube.com/channel/UChWZsjdoRvZ0T9QWZOD6UpA 🔥 Members Only Content https://www.youtube.com/playlist?list=UUMO_ML5xP23TOWKUcc-oAE_Eg 🏭 Backend Engineering Videos in Order https://backend.husseinnasser.com 💾 Database Engineering Videos https://www.youtube.com/playlist?list=PLQnljOFTspQXjD0HOzN7P2tgzu7scWpl2 🎙️Listen to the Backend Engineering Podcast https://husseinnasser.com/podcast Gears and tools used on the Channel (affiliates) 🖼️ Slides and Thumbnail Design Canva https://partner.canva.com/c/2766475/647168/10068 Stay Awesome, Hussein