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fsfs7 structure-indexes - questions

From: Daniel Shahaf <d.s_at_daniel.shahaf.name>
Date: Sun, 17 May 2015 23:20:47 +0000

Good morning Stefan,

A couple of questions on the fsfs7 indexes doc:

[[[
--- subversion/libsvn_fs_fs/structure-indexes
+++ subversion/libsvn_fs_fs/structure-indexes
@@ -18,6 +18,9 @@ a simple concatenation of runtime structs and as such, an implementation
 detail subject to change. A proto index basically aggregates all the
 information that must later be transformed into the final index.
 
+### "Subject to change?" The format must be stable & documented since
+### "begin txn, modify txn, reboot, upgrade svn, commit txn" should work.
+
 
 General design concerns
 -----------------------
@@ -346,7 +349,10 @@ For performance reasons we use a modified version:
 * combine the big endian representation of these checksums plus the
   remnant of the original stream into a 12 to 15 byte long intermediate
 
   [i0 .. iK], 12 <= K+1 <= 15
 
+### "combine" is unclear. Combine how? Concatenate? Interleave? Add? Multiply?
+
 * FNV checksum = fnv_1a([i0 .. iK]) in big endian representation
 
+### Why do we checksum the output of a checksum algorithm? (Bytes i0..iK are themselves FNV output)
]]]

Also, I suggest to change "zero to many" to "zero or more" to avoid confusion
with the term "one-to-many" of relational databases.

Cheers,

Daniel
Received on 2015-05-18 01:22:59 CEST

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