[Xapian-tickets] [Xapian] #823: Unit test ioblock1 failure

[Xapian]

#823: Unit test ioblock1 failure
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 Reporter:  someplaceguy  |             Owner:  Olly Betts
     Type:  defect        |            Status:  new
 Priority:  normal        |         Milestone:  1.4.25
Component:  Test Suite    |           Version:  1.4.24
 Severity:  normal        |        Resolution:
 Keywords:                |        Blocked By:
 Blocking:                |  Operating System:  Linux
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Comment (by someplaceguy):

 Unfortunately the accuracy/timeliness of `st_blocks` seems to be a bit of
 a complicated issue in ZFS.

 Perhaps the best course of action would be to perform 2 tests for
 sparsity:

 1) The first test would follow the suggestion of the ZFS developer to use
 lseek(SEEK_DATA/SEEK_HOLE) to figure out whether the file has holes or not
 (i.e. indicating that it is sparse). This would work for ZFS and all other
 filesystems that implement this interface.

 2) However, some filesystems might not implement this interface and
 instead they might claim that the entire file is a non-hole even though
 they do support sparse files. As a fallback, a second test would be
 performed, using `st_blocks` like Xapian currently does.

 This should probably be robust enough to work in almost all cases.
-- 
Ticket URL: <https://trac.xapian.org/ticket/823#comment:4>
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