On Wed, 5 Sep 2007, Jon Smirl wrote:
On 9/5/07, Andreas Ericsson <ae@xxxxxx> wrote:
Jon Smirl wrote:
The path name field needs to be moved back into the blobs to support
alternative indexes. For example I want an index on the Signed-off-by
field. I use this index to give me the SHAs for the blobs
Signed-off-by a particular person. In the current design I have no way
of recovering the path name for these blobs other than a brute force
search following every path looking for the right SHA.
Ah, there we go. A use-case at last :)
But not a brilliant one. You sign off on commits not blobs. So you go
from the sign-off to paths, then to blobs. There is no need to go from
blob to path unless you deliberately introduce such a need.
So now we have a concrete problem that we can formulate thus:
"How can one create a database listing the relationship between 'signers'
and blobs?"
So the second question: Do you seriously argue that git should take a
huge performance loss on its common operations to accommodate a need that
I suspect very few people have?
Why do you keep jumping to a performance loss? Both schemes will have
an index based on paths. The problem is how those indexes are
constructed, not the existence of the index. Moving the paths into the
blobs in no way prevents you from creating an index on that field.
But moving the path into the blob _IS_ the perfomance hit. You lose the
ability to tell the two files have the same content _without even looking
at the blob_. This is one of the core parts of making git operations
blindingly fast. You can't throw that out, and then say that there is no
performance hit.
You keep talking about abstract database performance - but git is not an
abstract database. It has very specific common usage patterns, and is
optomisied to handle them.
The problem is that the SHAs have been intertwined with the tree
nodes. This blending has made it impossible to create other indexes on
the blobs.
The path index in the flat scheme will probably look just like tree
nodes do today but these new tree nodes won't be intertwined with the
SHAs.
And you will have to prove that diff/merge etc. don't become very much
slower before you get buy in.
--
Julian
---
Many receive advice, few profit by it.
-- Publilius Syrus
-
To unsubscribe from this list: send the line "unsubscribe git" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
