# Linux Kernel in PostgreSQL via pgit

Oliver Seifert imported the entire Linux kernel git history — 1,428,882 commits, 24.4 million file versions, 20 years of development — into PostgreSQL using [[pgit]], his Go CLI backed by delta-compressed storage. The point isn't to replace git. It's to make git history queryable with SQL, and the article demonstrates this by running a series of analyses that would be painful or impossible with git log alone.

## The import

The full kernel imported in about 2 hours on a 24-core Hetzner box with 512 GB RAM. Actual data on disk: 2.7 GB, a 53.5x compression ratio over raw uncompressed git objects. Git's own `gc --aggressive` compresses better (74.1x, 1.95 GB), but git's pack format isn't queryable — pgit's is.

The compression comes from pg-xpatch, a PostgreSQL Table Access Method that stores delta-compressed data. Text content (1.3 GB) and commits (600 MB) compress well; file references (the mapping from commits to paths to blobs) take up 2.1 GB and dominate storage.

## What SQL reveals about the kernel

The interesting part of the article is the queries. A few highlights:

**The committer bottleneck.** 38,506 unique authors but only 1,540 committers — a 25:1 ratio. Three people (David S. Miller, Greg Kroah-Hartman, Linus Torvalds) merged 22.5% of all commits. Miller alone accounts for 7.9%. The kernel's merge hierarchy concentrates enormous trust in a small group.

**One-time contributors.** 14,000 authors submitted exactly one patch and never came back. That's 36% of all authors. Individual (Gmail) contributions peaked at 12% in 2010 and fell to 8% by 2025 — the kernel is increasingly corporate.

**Small commits dominate.** 61.3% of commits touch a single file. 90% touch 5 or fewer. The rare huge commits (up to 53,003 files) are merge commits from subsystem maintainers.

**GPU drivers are uniquely messy.** The Intel i915 driver appears 8 times in the top 30 file-coupling pairs. GPU drivers (amd/display, amdgpu, i915) account for ~516 reverts — nearly 10% of all reverts in the kernel. Hardware driver development against moving specs produces churn that other subsystems don't see.

**The "buggiest" commit.** Linus's initial git import (`1da177e4c3f4`) has 665 Fixes: references pointing at it, because it's used as shorthand for bugs that existed before git history began.

**Kent Overstreet's 13-year bcachefs journey.** From initial commit in 2011 through mainline merge in 2023, with 1,194 commits that year alone.

## Query performance

All queries ran without materialized views or preprocessing. Most completed in under 3 seconds over 24.4 million file references. The expensive ones were file coupling (48s, requires self-joining the file reference table) and full-text search across all commit messages (44s). Practical for interactive exploration.

## Cross-references

- [[pgit]] — the tool itself (toolbox page)
- [[git-magic-files]] — another angle on git's internal machinery
- [[postgresql]] — the database underneath