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MVCC (Multiversion Concurrency Control)

MVCC (ya Multiversion Concurrency Control) ek database concurrency control technique hai jisme data…

Overview
🌟

MVCC (Multiversion Concurrency Control) — Quick Facts

📌

Property: Detail

🎯

Full Name: Multiversion Concurrency Control

Abbreviation: MVCC

🔑

Type: Concurrency Control Mechanism

Topic 1
📥 📥 🧠 🔬 💡 🎯

Infobox

📚 | Property | Detail | |---|---| | Full Name | Multiversion Concurrency Control | |…
Topic 2
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Overview

💡

Option A: Lock-based — reader ko…

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Option B: MVCC — writer naya…

Multi — ek data item ke multiple…

🎯

Version — har write operation ek…

Topic 3

Background: Concurrency Problem

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Shared Lock (S-lock): Multiple…

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Exclusive Lock (X-lock): Sirf ek…

Two-Phase Locking (2PL):…

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Reader blocks writer: Jab koi row…

Topic 4

Concurrency Anomalies

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Transaction A ne row update kiya…

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Transaction B woh uncommitted data…

Agar A rollback kare, to B ne…

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MVCC prevention: B ko sirf…

Topic 5
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How MVCC Works

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Purani row delete nahi hoti — woh…

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Ek new version create hoti hai…

Dono versions me metadata hota…

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Har transaction ko ek unique,…

Topic 6

MVCC Version Chain Diagram

`mermaid sequenceDiagram participant TX100 as Transaction 100 participant DB as Database…
Topic 7

MVCC vs Lock-Based Concurrency

🌟 | Aspect | MVCC | Lock-Based (2PL) | |---|---|---| | Core Mechanism | Multiple data…
Topic 8

Transaction Isolation Levels aur MVCC

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MVCC me practically use nahi hota

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Dirty reads allowed hain (uncommon…

Most MVCC databases is level ko…

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Har statement ke liye naya…

Topic 9
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MVCC in PostgreSQL

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xmin: Woh transaction ID jisne yeh…

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xmax: Woh transaction ID jisne yeh…

Old row ka xmax set hota hai…

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New row create hoti hai with new…

Topic 10

MVCC in MySQL InnoDB

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Clustered Index: Primary key ke…

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Undo Log: Purane versions undo log…

Read View: Transaction start hote…

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Purani row ka data undo log me…

Topic 11
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MVCC in Oracle

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System Change Number (SCN):…

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Undo Tablespace: Old data versions…

Consistent Read: Har query ko us…

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Read Consistency: Oracle me by…

Topic 12

MVCC in Other Databases

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By default SQL Server lock-based…

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Snapshot Isolation enable karne…

Row versions tempdb me store hoti…

🎯

READ_COMMITTED_SNAPSHOT isolation…

Topic 13

Database MVCC Implementation Comparison

🔑 | Database | MVCC Type | Old Version Storage | Cleanup | Default Isolation | Timestamp…
Topic 14
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Garbage Collection aur Version Cleanup

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Dead tuples (old versions jo kisi…

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Space OS ko return nahi karta —…

Non-blocking — normal operations…

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autovacuum daemon periodically…

Topic 15
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Write Conflicts aur Resolution

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Jo transaction pehle write kare,…

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Baad wala transaction…

Application retry kar sakti hai

🎯

Application-level decision — later…

Topic 16
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Advantages of MVCC

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Readers kabhi block nahi hote —…

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Read-heavy workloads me dramatic…

OLTP systems jahan high read…

🎯

Read operations koi lock acquire…

Topic 17
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Disadvantages of MVCC

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Multiple versions physically…

🔑

PostgreSQL me table bloat ho sakta…

InnoDB me undo log grow ho sakta…

🎯

Additional storage cost

Topic 18
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MVCC in Distributed Databases

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Clock Synchronization: Different…

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Global Snapshots: Distributed…

Version Propagation: Ek node par…

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Hardware-based GPS + atomic clocks…

Topic 19

Best Practices

🎯 For Application Developers 1. Transactions chhote rakho — long-running transactions old…
Comparison

MVCC vs Lock-Based Concurrency

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Core Mechanism: Multiple data versions

⚖️

Readers block Writers?: No ❌

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Writers block Readers?: No ❌

Comparison

Database MVCC Implementation Comparison

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PostgreSQL: Append-only (new tuple)

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MySQL/InnoDB: In-place + Undo

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Oracle: In-place + Undo

Diagram
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Visual Flow

📊 Diagram visualization — details in narration
Related Topics

See Also

📖

Database_transaction

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Concurrency_control

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ACID

📚

Transaction_isolation

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Deadlock

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PostgreSQL

Quick Quiz
🧠 QUIZ TIME

Quiz — Question 1

MVCC (Multiversion Concurrency Control) ka sabse sahi definition kya hai?

Quick Quiz
🧠 QUIZ TIME

Quiz — Question 2

MVCC (Multiversion Concurrency Control) ka 'Full Name' kya hai?

Complete! 🎉
COMPLETE

MVCC (Multiversion Concurrency Control) Complete!

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MVCC (Multiversion Concurrency Control) Complete

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