[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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Changes (by Olly Betts):

 * milestone:   => 1.4.25

Comment:

 Ah, so the block count is of compressed blocks, not of the blocks of data
 that are the contents of the file.

 This check could be weakened to `>= 1` since the data can't compress to
 nothing, but I think we could easily write pseudo-random data which
 shouldn't compress significantly and thus allow the existing check to work
 in your case.

 Such compression makes the following check for whether the current FS
 supports sparse files or not trickier, at least if there's an FS that
 supports compression like this but doesn't support (or allows turning off
 support for) sparse files - the blocks without data written are all-zero
 so they'd compress really well which looks a lot like sparse files.
 However I think it doesn't matter for what the testcase actually needs to
 know - it wants to test writing a block over 4GB into a file works
 correctly, and the concern is avoiding creating an enormous temporary file
 - sparse files allow that, but so should FS-level compression.  Just
 tweaking the comments and messages is probably enough there.
-- 
Ticket URL: <https://trac.xapian.org/ticket/823#comment:1>
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