my db engine

just a toy database engine i wrote in c++.

it's not for production, just shows how a db works under the hood. the core logic is in the datbase_engine.cpp, and the test/demo is in db_test.cpp.

features

• saves data to database.dat
• uses a b+ tree for the index (in memory) so it's fast
• has a simple cache (lru)
• writes to a journal.log first so it doesn't break if it crashes

how to build

you need a c++ compiler. just compile the test file with optimizations so the benchmark is accurate.

g++ -o db_test db_test.cpp -std=c++17 -O3

running

just run the exe it makes.

./db_test

test output

here's what i got on my machine. the index is way faster than just reading the whole file.

╔══════════════════════════════════════════════════════╗
║     MINI DATABASE ENGINE - C++ Implementation        ║
╚══════════════════════════════════════════════════════╝

► PART 1: Basic read/write test
━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━

Inserting a few records...
OK, 5 records in.

Now, let's try to get them back.
  Get user:1001... Alice Johnson
  Get product:5001... Laptop - $1299
  Get user:9999... NOT FOUND

Updating user:1002...
  -> New value: Bob Smith (Updated)

Deleting product:5002...
  -> Verify delete: OK, gone.


► PART 2: Bulk Insert (Stress Test)
━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━

Alright, let's hammer it. Inserting 10000 records........
Done. Took 163 ms
  -> Throughput: 61349.7 inserts/sec


► PART 3: Speed Test (Index vs. Full Scan)
━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━

Testing FAST (BTree) search...
  -> Found 5/6 keys
  -> Took: 45 us (microseconds)

Testing SLOW (linear file scan)...
  -> Found 6/6 keys
  -> Took: 26637 us (microseconds)

[SPEEDUP ANALYSIS]
  Indexed search is 591.9x faster!
  Time saved: 26592 us


► PART 4: Database Statistics
━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━
=== Database Statistics ===
File size: 40984576 bytes
Number of pages: 10006
Page size: 4096 bytes
Cache size: 100 pages

╔══════════════════════════════════════════════════════╗
║     Demo Complete! Database files saved to disk.     ║
╚══════════════════════════════════════════════════════╝