[Xapian-tickets] [Xapian] #491: calling replace_document() twice doubles the size of the database

[Xapian]

#491: calling replace_document() twice doubles the size of the database
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 Reporter:  maad    |        Owner:  olly   
     Type:  defect  |       Status:  closed 
 Priority:  normal  |    Milestone:         
Component:  Other   |      Version:         
 Severity:  major   |   Resolution:  invalid
 Keywords:          |    Blockedby:         
 Platform:  All     |     Blocking:         
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Comment(by olly):

 We do actually check that.  But to commit the table, we need a new root
 block.  So if you replace a million documents with themselves, you should
 see the table sizes increase by a single block (8KB by default).  So it's
 only "doubles the size" if your database tables are only 8KB to start
 with.

 The new Btree manager I'm working on (see browser:branches/brass-btree for
 the code) reuses the existing root block in this case.

 It would be nice to reuse the root block in the current backends too, but
 when I looked briefly at trying to avoid committing unmodified tables some
 years ago, the obvious simple change didn't worked, so I think somewhere
 assumes that the revision number stored in the root block is that of the
 latest revision.

 If you want to work on a patch to achieve this for the current chert
 backend, feel free - chert_table.cc and chert_database.cc are the files to
 look at.  If the patch looks sane and the test coverage for it is good, I
 would support applying it.

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Ticket URL: <http://trac.xapian.org/ticket/491#comment:3>
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