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Re: [PATCH] Optionally use deltas in dumpfiles

From: Greg Hudson <ghudson_at_MIT.EDU>
Date: 2004-03-29 04:22:11 CEST

On Sun, 2004-03-28 at 21:09, C. Michael Pilato wrote:
> I don't have time to read/review the patch right now, so I'll stick to
> asking questions that I feel you owe us as a penalty for dropping
> another code bomb. :-)

> - Against what are the deltas for a given node? The previous node?

Answer #1: against the same thing we compare against to decide if text
and properties have changed. That had better be the right thing, or
there would be situations where a dump/load doesn't change a node which
ought to change. If you look at the changes to dump_node, you can see
that I just expanded the scope of compare_root and used
compare_root/compare_path as the delta source.

(I actually went to significant effort to try to conduct a case where
the code compares against the wrong thing--by constructing a rev where a
directory is replaced with copy history and then a file within it is
modified to have the same contents as the previous rev had at that
path--but you guys were too clever, and had already taken care of it.
So no torturous ghudson bugs to report on that front.)

Answer #2:

  * For an add with history, the copy history.
  * For an add without history, the empty source.
  * For a change, the previous contents of the node.

Answer #3: the same thing the delta would be against for a commit.

> - In what situations are deltas used: adds-with-history?
> adds-without-history? modifications?

In all three situations. (In the patch I sent, adds-without-history are
dumped as plain text rather than as deltas against empty, but it's a
trivial one-line change to fix that.)

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Received on Mon Mar 29 04:22:34 2004

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