Fossil

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Overview
Comment:More refactoring of "control artifact" to "structural artifact". Also improve the wording. All in the selfcheck document.
Downloads: Tarball | ZIP archive | SQL archive
Timelines: family | ancestors | descendants | both | trunk
Files: files | file ages | folders
SHA3-256: 43c3d95a31c486ae18e46013db1287aeb5401786997585386a4fa77681ead3f5
User & Date: drh 2017-03-12 23:32:49
Context
2017-03-13
20:47
Fix a obsolete comment related to updating the CHECK constraint on the BLOB table when moving up to version 2.0 or later. check-in: 66807d30 user: drh tags: trunk
01:12
Add the capability for Fossil to directly interpret the Authentication: HTTP header for Basic Authentication, if enabled on the /setup_access page. Disabled by default. Closed-Leaf check-in: 4fa4c021 user: drh tags: basic-authentication-2
2017-03-12
23:32
More refactoring of "control artifact" to "structural artifact". Also improve the wording. All in the selfcheck document. check-in: 43c3d95a user: drh tags: trunk
18:59
Use the term "structural artifacts" in place of the older "control artifact" notation. check-in: 1dda1b6d user: drh tags: trunk
Changes
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Changes to www/selfcheck.wiki.

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the repository checksum is verified after a checkout to make
sure that the entire repository was checked out correctly.
Note that these added checks use a different hash algorithm (MD5)
in order to avoid common-mode failures in the hash
algorithm implementation.


<h2>Checksums On Control Artifacts And Deltas</h2>

Every [./fileformat.wiki | control artifact] in a fossil repository
contains a "Z-card" bearing an MD5 checksum over the rest of the
artifact.  Any mismatch causes the control artifact to be ignored.

The [./delta_format.wiki | file delta format] includes a 32-bit
checksum of the target file.  Whenever a file is reconstructed from
a delta, that checksum is verified to make sure the reconstruction
was done correctly.

<h2>Reliability Versus Performance</h2>
................................................................................
Fossil takes the philosophy of the
<a href="http://en.wikipedia.org/wiki/The_Tortoise_and_the_Hare">tortoise</a>:
reliability is more important than raw speed.  The developers of
fossil see no merit in getting the wrong answer quickly.

Fossil may not be the fastest versioning system, but it is "fast enough".
Fossil runs quickly enough to stay out of the developers way.
Most operations complete in under a second.








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the repository checksum is verified after a checkout to make
sure that the entire repository was checked out correctly.
Note that these added checks use a different hash algorithm (MD5)
in order to avoid common-mode failures in the hash
algorithm implementation.


<h2>Checksums On Structural Artifacts And Deltas</h2>

Every [./fileformat.wiki | structural artifact] in a fossil repository
contains a "Z-card" bearing an MD5 checksum over the rest of the
artifact.  Any mismatch causes the structural artifact to be ignored.

The [./delta_format.wiki | file delta format] includes a 32-bit
checksum of the target file.  Whenever a file is reconstructed from
a delta, that checksum is verified to make sure the reconstruction
was done correctly.

<h2>Reliability Versus Performance</h2>
................................................................................
Fossil takes the philosophy of the
<a href="http://en.wikipedia.org/wiki/The_Tortoise_and_the_Hare">tortoise</a>:
reliability is more important than raw speed.  The developers of
fossil see no merit in getting the wrong answer quickly.

Fossil may not be the fastest versioning system, but it is "fast enough".
Fossil runs quickly enough to stay out of the developers way.
Most operations complete in milliseconds, faster that you can press
the "Enter" key.