Concurrency control | Transaction processing
In databases an index is a data structure, part of the database, used by a database system to efficiently navigate access to user data. Index data are system data distinct from user data, and consist primarily of pointers. Changes in a database (by insert, delete, or modify operations), may require indexes to be updated to maintain accurate user data accesses. Index locking is a technique used to maintain index integrity. A portion of an index is locked during a database transaction when this portion is being accessed by the transaction as a result of attempt to access related user data. Additionally, special database system transactions (not user-invoked transactions) may be invoked to maintain and modify an index, as part of a system's self-maintenance activities. When a portion of an index is locked by a transaction, other transactions may be blocked from accessing this index portion (blocked from modifying, and even from reading it, depending on lock type and needed operation). Index Locking Protocol guarantees that phantom read phenomenon won't occur. Index locking protocol states: * Every relation must have at least one index. * A transaction can access tuples only after finding them through one or more indices on the relation * A transaction Ti that performs a lookup must lock all the index leaf nodes that it accesses, in S-mode, even if the leaf node does not contain any tuple satisfying the index lookup (e.g. for a range query, no tuple in a leaf is in the range) * A transaction Ti that inserts, updates or deletes a tuple ti in a relation r must update all indices to r and it must obtain exclusive locks on all index leaf nodes affected by the insert/update/delete * The rules of the two-phase locking protocol must be observed. Specialized concurrency control techniques exist for accessing indexes. These techniques depend on the index type, and take advantage of its structure. They are typically much more effective than applying to indexes common concurrency control methods applied to user data. Notable and widely researched are specialized techniques for B-trees which are regularly used as database indexes. Index locks are used to coordinate threads accessing indexes concurrently, and typically shorter-lived than the common transaction locks on user data. In professional literature, they are often called . (Wikipedia).
Combination Locks - Intro to Algorithms
This video is part of an online course, Intro to Algorithms. Check out the course here: https://www.udacity.com/course/cs215.
From playlist Introduction to Algorithms
Geneva Wheel for Precise Indexing
A modified type of Geneva wheel that was developed to obtain precise intermittent indexing movements. This special mechanism was designed to eliminate any backlash or over-running action of the driven member at the end or beginning of each indexing movement. It uses a double locking, with
From playlist Geneva Mechanisms
This is an indexer mechanism. It uses a combination of two intermittent mechanisms. A mutilated gear determines the still/moving cycle times. And a geneva mechanism makes the movement and locks the driven wheel.
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Make A Combination Lock - Intro to Algorithms
This video is part of an online course, Intro to Algorithms. Check out the course here: https://www.udacity.com/course/cs215.
From playlist Introduction to Algorithms
Make A Combination Lock - Intro to Algorithms
This video is part of an online course, Intro to Algorithms. Check out the course here: https://www.udacity.com/course/cs215.
From playlist Introduction to Algorithms
How to Lock and Protect Individual Cells in Excel + Bonus Tips for Quick Setup
Sign up for our Excel webinar, times added weekly: https://www.excelcampus.com/blueprint-registration/ In this video I explain how to lock & protect individual cells or ranges for editing. This is useful when you only want users to be able to edit specific cells and protect other cells t
From playlist Excel Formulas
Samsung Galaxy S5 customization - set up lock screen
In this video we teach you how to set up the Samsung Galaxy S5 lock screen to provide some security for your phone.
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Counting: Find the Number of Lock Combinations
This video explains how to determine the number of lock combinations are possible.
From playlist Counting (Discrete Math)
This LOCK is NOT What it Seems!! - Solving the CHALLENGING Lock Puzzle!
B Lock Puzzle: http://bit.ly/2Fx8urh Today I'm attempting to solve the infamous B Lock puzzle by Boaz Feldman. This lock puzzle is very difficult and can be used as an actual lock! The secret to opening is contained within the lock and key. Enjoy! OTHER LOCK PUZZLE VIDEO: https://www.you
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Set and reset index in DataFrames with Python | 1.7.5 Statistical analysis and data science course
Do you know the multiples ways to work with indices and data frames? In this chapter of the video series DataFrames in the tutorial course in statistics and data science with Python we will see the multiple ways to add indices and set new indices to Data Frames with python using Pandas.
From playlist Python
How to deal with index with iloc and loc in DataFrames Pandas | 1.7.3 Analysis Data science Python
Do you understand the differences between iloc and loc?? In this chapter of the video series DataFrames in the tutorial course in statistics and data science with Python we will see the multiple ways to explore Data Frames with python using iloc, loc, at and iat. - Defining a dataframe a
From playlist Python
RailsConf 2019 - rails db:migrate:safely by Matt Duszynski
RailsConf 2019 - rails db:migrate:safely by Matt Duszynski _______________________________________________________________________________________________ Cloud 66 - Pain Free Rails Deployments Cloud 66 for Rails acts like your in-house DevOps team to build, deploy and maintain your Rails
From playlist RailsConf 2019
So You Wanna Be a Pandas Expert? || James Powell
So… you want to be a Pandas expert. What’s it going to take? Should you memorize the Pandas API? Should you read through the source code, line-by-line, file-by-file? Should you try to write your own Pandas from scratch? Or could it be much simpler than that? Could there be an idea, a smal
From playlist Python
“There should be one—and preferably only one—obvious way to do it,” — Zen of Python. I certainly wish that were the case with pandas. In reading the docs it feels like there are a thousand ways to do each operation. And it is hard to tell if they do the exact same thing or which one you
From playlist Python pandas — An Opinionated Guide
PGConf NYC 2021 - Identifying Slow Queries and Fixing Them! by Stephen Frost
Identifying Slow Queries and Fixing Them! by Stephen Frost We'll be looking at PostgreSQL configuration options (postgresql.conf) for logging and basic tuning parameters, how to monitor which queries are taking the most time using pg_stat_statements, going over EXPLAIN and EXPLAIN ANALYZE
From playlist PGConf NYC 2021
Highline Excel Class 45: INDEX function & MATCH function 12 Unusual Examples
Download Excel Start File 1: https://people.highline.edu/mgirvin/YouTubeExcelIsFun/Week8Busn214.xls Download Excel Start File 2: https://people.highline.edu/mgirvin/YouTubeExcelIsFun/Week08Busn214DataTableExtraFile.xls Download Excel Finished File: https://people.highline.edu/mgirvin/YouTu
From playlist Excel INDEX & MATCH Function Formula videos
Highline Excel 2016 Class 11: Lookup Functions & Formulas, Comprehensive Lessons, 20 Examples
Download Files: https://people.highline.edu/mgirvin/AllClasses/218_2016/218Excel2016.htm In this video learn about: (00:12) Introduction 1. (00:51) Data Validation List. VLOOKUP, Exact Match. IF & ISBLANK functions. Goal: Create Invoice. 2. (09:43) HLOOKUP with Exact Match Lookup. Goal: L
From playlist Excel Advanced Free Course at YouTube. Comprehensive Excel 2016: Calculations & Data Analysis (27 Videos)
Indexing and Selecting - Pandas
“There should be one—and preferably only one—obvious way to do it,” — Zen of Python. I certainly wish that were the case with pandas. In reading the docs it feels like there are a thousand ways to do each operation. And it is hard to tell if they do the exact same thing or which one you
From playlist Python pandas — An Opinionated Guide
Intermediate Python Programming Course
Take your Python skills to the next level with this intermediate Python course. First, you will get a review of basic concepts such as lists, strings, and dictionaries, but with an emphasis on some lesser known capabilities. Then, you will learn more advanced topics such as threading, mult
From playlist Python Tutorials
http://www.mekanizmalar.com/menu_index.html The output in this simple mechanism is prevented from turning in either direction unless it is actuated by the input motion. In operation, the drive lever indexes the output disk by bearing on the pin.
From playlist Indexing