CSCI-550: PostgreSQL Buffer Management Enhancement

Project Overview

This project enhances PostgreSQL 16.4 by introducing a FIFO (First-In-First-Out) buffer replacement strategy alongside the existing LRU Clock-Sweep algorithm.
The FIFO strategy manages buffers in strict queue order, replacing the oldest buffer first when needed.

This work was developed as part of CSCI-550 (Advanced Database Systems) at USC.

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Files Modified

• src/backend/storage/buffer/freelist.c

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Key Changes

1. Implemented a FIFO queue (FifoQueue) to track buffers in insertion order.
2. Added functions to enqueue (enqueueBuffer) and dequeue (dequeueBuffer) buffers from the queue.
3. Modified buffer selection logic (GetNewBuffer and GetVictimBuffer) to integrate FIFO.
4. Introduced a toggle flag (enable_fifo) in BufferStrategyControl to switch between FIFO and LRU Clock-Sweep.
5. Updated StrategyGetBuffer to dynamically select the appropriate replacement strategy.

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Usage

• Set the enable_fifo flag:
  • enable_fifo = true → Buffers are allocated/replaced using FIFO.
  • enable_fifo = false → PostgreSQL’s default LRU Clock-Sweep strategy is used.

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Results

• With FIFO enabled, buffer replacement follows strict insertion order.
• With LRU Clock-Sweep, PostgreSQL’s adaptive buffer strategy is preserved.

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Attribution

This project builds on the official PostgreSQL 16.4 source code.
The modifications here are for educational purposes only and represent enhancements implemented by our group.