Build a working SQL database engine in C++20 -- from an empty directory to
a query processor that runs real SQL against data on disk -- through a
single relentless method: nothing is asserted; everything is demonstrated.
Every data structure in this book is built, compiled, and run. Every
performance claim is a table printed by a benchmark whose source code is on
the page in front of you. Every design decision is followed by the
measurement that justifies it -- and, where the design has a cost, by the
measurement that exposes that cost too. And once per unit, something fails
in front of you: a real bug, reproduced deterministically, diagnosed from
the evidence, fixed, and locked shut with a regression test.
This is not a survey of database theory. It is a lab manual. You will not
find hand-waving about how B+Trees are "generally logarithmic" -- you will
find the fan-out arithmetic, the page-count math, and a benchmark that
walks a tree of a million keys and prints the real number.
This book takes the engine across two complete parts and eight units:
PART I -- STORAGE
1. Slotted Pages & the Pager -- self-describing 4 KiB pages, records with
stable slot ids, a pager with a free list
2. B+Tree: Insert & Search -- logarithmic lookup, proven against a
million-key tree
3. B+Tree: Delete & Range Scans -- rebalancing, merges, ordered range
queries
4. The Buffer Pool -- a real cache with clock eviction, measured 2.5x
faster with identical logical work
PART II -- FROM BYTES TO A QUERY
5. The Record Layer -- typed rows: a schema-aware codec and a table heap,
reached by key through the index
6. The Catalog -- persistent schemas and named tables: the engine's
self-knowledge
7. The Front End -- a SQL tokenizer and recursive-descent parser, with
compiler-quality caret-pointed errors
8. The Executor -- the milestone: a real executor that runs CREATE TABLE,
INSERT, and SELECT end to end, against a database of hundreds of
thousands of rows
By the last page, the engine answers a SQL query it parsed from text,
against rows it stored on disk, through an index it built and a cache it
manages itself -- and every number in the book came from actually running
that code.
Reference machine: g++ 13.3.0, Ubuntu 24.04, C++20, stdlib + POSIX only.
Every benchmark ships with the exact command that produced it, so you can
run it yourself and get the same structural numbers.
Development Methodology
This book was created through a process that combines careful human planning, content direction, and advanced AI technology, followed by thorough refinement and review to ensure a high-quality final work.
A companion volume, "Build a SQL Database Engine in C++, Book 2: Parts III
& IV," continues the engine into durability (crash recovery via a
write-ahead log), concurrency, and performance -- available separately, and
as a discounted bundle with this book.
