git/list[1] front-page[2] threads[3] people[4] search[5] about
 

Re: New Feature wanted: Is it possible to let git clone continue last break point?

From
Shawn Pearce <spearce@spearce.org>
Date
Nov 4, 2011, 14:22 UTC
Message-ID
<CAJo=hJtsiEEHA33CQn1MCvb7vFv7uEF+U292YgBa7EWv7P8Jng@mail.gmail.com>
In-Reply-To
<4EB3B1E7.7080507@viscovery.net>
On Fri, Nov 4, 2011 at 02:35, Johannes Sixt <j.sixt@viscovery.net> wrote:
Show 6 quoted lines
> Am 11/4/2011 9:56, schrieb Clemens Buchacher:
>> Cache ... not the pack but the information
>>    to re-create it...
>
> It has been discussed. It doesn't work. Because with threaded pack
> generation, the resulting pack is not deterministic.

The information to create a pack for a repository with 2M objects (e.g. Linux kernel tree) is *at least* 152M of data. This is just a first order approximation of what it takes to write out the 2M SHA-1s, along with say a 4 byte length so you can find given an offset provided by the client roughly where to resumse in the object stream. This is like 25% of the pack size itself. Ouch.

This data is still insufficient to resume from. A correct solution would allow you to resume in the middle of an object, which means we also need to store some sort of indicator of which representation was chosen from an existing pack file for object reuse. Which adds more data to the stream. And then there is the not so simple problem of how to resume in the middle of an object that was being recompressed on the fly, such as a large loose object.

By the time you get done with all of that, your "ticket" might as well be the name of a pack file. And your "resume information" is just a pack file itself. Which would be very expensive to recreate.

Previous: Johannes SixtNext: Jakub Narebski
Message 13 of 18 in “New Feature wanted: Is it possible to let git clone continue last break point?”
  1. netrobyOct 31, 2011
  2. Tay Ray ChuanOct 31, 2011
  3. Jonathan NiederOct 31, 2011
  4. netrobyOct 31, 2011
  5. Jeff KingNov 2, 2011
  6. Junio C HamanoNov 2, 2011
  7. Jeff KingNov 2, 2011
  8. Shawn PearceNov 3, 2011
  9. Jeff KingNov 3, 2011
  10. Shawn PearceNov 3, 2011
  11. Clemens BuchacherNov 4, 2011
  12. Johannes SixtNov 4, 2011
  13. Shawn PearceNov 4, 2011
  14. Jakub NarebskiNov 4, 2011
  15. Nguyen Thai Ngoc DuyNov 4, 2011
  16. Clemens BuchacherNov 5, 2011
  17. Jakub NarebskiOct 31, 2011
  18. Michael SchubertOct 31, 2011

Read the whole thread, see it on lore, or plain text.

$ cat FOOTERMessages come from the public archive at lore.kernel.org/git, fetched every hour. The front page is chosen and written each morning by an AI editor and can be wrong; the threads themselves are the record. About and API. For agents: an MCP server at https://gitlist.dev/mcp, and any thread, story or person page as Markdown by adding .md to its URL (or sending Accept: text/markdown). Details in /llms.txt.