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In fact, git stores a full snapshot of your entire repo with every commit. It does not store diffs from the previous commit. When you do "git show <COMMIT_SHA>"

In fact, git stores a full snapshot of your entire repo with every commit. It does not store diffs from the previous commit. When you do "git show <COMMIT_SHA>" it generates a diff from the parent commit on the fly. There's a huge optimization though: it uses a content-addressed blob store, where everything is referenced by the sha1 of its contents. So if a file's contents is exactly the same between two commits, it ends up using the same blob. They don't have to be sequential commits, or it could even be two different file paths in the same commit. Git doesn't care - it's a "dumb content tracker". If one character of a file is different, git stores a whole separate copy of the file for it. But every once in a while it packs all blobs into a single file, and compresses the whole thing at once, and the compression can take advantage of blobs which are very similar.

6t6t6t6 8y ago
Yeah... My comment was an oversimplification, but you get the point. :) With event sourcing there's also the concept of snapshotting, btw.
mbrock 8y ago
Also directory structures are content-addressed, so if a commit changes nothing in a given directory, the commit data won't duplicate the listing of that directory.
bonesss 8y ago
Gits bi-modal nature is a wonderful representation of a sanely architected Event Sourced system. When needed it can create a delta-by-delta view of the world for processing, but for most things most of the time it shows a file-centric view of the world. IMO a well-factored event sourced system isn't going to feel 'event sourced' for most integrated components, APIs, and services because it's working predominately with snapshots and materialized views. For compex process logic, or post-facto analysis, the event core keeps all the changes available for processing. Done right it should feel like a massive win/win. Done wrong and it's going to feel hard in all the wrong places :)

6t6t6t6 8y ago

Yeah... My comment was an oversimplification, but you get the point. :) With event sourcing there's also the concept of snapshotting, btw.

mbrock 8y ago

Also directory structures are content-addressed, so if a commit changes nothing in a given directory, the commit data won't duplicate the listing of that directory.

bonesss 8y ago

Gits bi-modal nature is a wonderful representation of a sanely architected Event Sourced system. When needed it can create a delta-by-delta view of the world for processing, but for most things most of the time it shows a file-centric view of the world. IMO a well-factored event sourced system isn't going to feel 'event sourced' for most integrated components, APIs, and services because it's working predominately with snapshots and materialized views. For compex process logic, or post-facto analysis, the event core keeps all the changes available for processing. Done right it should feel like a massive win/win. Done wrong and it's going to feel hard in all the wrong places :)