https://bugzilla.samba.org/show_bug.cgi?id=6946
Summary: Enable timestamp comparison with multiple file owners
Product: rsync
Version: 3.1.0
Platform: Other
OS/Version: Linux
Status: NEW
Severity: enhancement
Priority: P3
Component: core
AssignedTo: way...@samba.org
ReportedBy: ja...@phsys.co.uk
QAContact: rsync...@samba.org
Currently if multiple users using group write permissions update the same
folder then they can't always update file timestamps. This is because the file
may be owned by a separate user. Furthermore, changing the timestamp may be
undesirable if files are being updated from various sources, since timestamps
moving backwards can confuse some software.
Disabling timestamp updates does not impair rsync's functionality but it can
severely reduce performance. It is forced to fully read each file, on both
sides of the transfer, in order to obtain a checksum.
I propose caching these checksums, against a file's timestamp, in order to
avoid this performance problem. This method does not require an update of the
file's timestamp. It would require a database of some sort linking files and
timestamps to the calculated checksum. Whenever a file's timestamp changed, the
checksum would need recalculating.
To operate efficiently this would need to operate at both sides of the
connection. Basically instead of reading a file to determine its timestamp the
cache would first be checked. If the cache did not contain a timestamp then it
would be calculated and stored in the cache for future reference.
I'd suggest specifying the cache location for local and remote connections via
a parameter initially.
I intend to have a go at adding this functionality myself, although I'd be very
interested to hear any comments. Also if anyone has done anything similar, or
if I am missing some simpler solution to this problem.
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