[INN] #62: Internals documentation for buffindexed

[INN]

#62: Internals documentation for buffindexed
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 Reporter:  eagle        |       Owner:  eagle
     Type:  enhancement  |      Status:  new  
 Priority:  low          |   Milestone:       
Component:  doc          |     Version:       
 Severity:  wishlist     |    Keywords:       
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 We should have internals documentation for buffindexed and a detailed
 document of the on-disk format.  Here are some notes from Katsuhiro
 Kondou:

 Buffindexed has two functions.

  1. block manager
  2. overview data/index manager

 Block manager:

 All buffers are divided into 8KB block, and there is a bit map like cnfs.
 The block can be used for both overview data and index.  Block manager
 does not care the usage of the block.  It just gives a free block and
 frees it if required.

 Overview data/index manager:

 There is group.index which gives the pointer to each newsgroup info, hash
 of the group, the number of article in the group, hi/lo mark and the flag.
 That pointer includes where are base index block, last index block,
 current index block, the next block of current index and current overview
 data block.  Index block includes a series of token, arrival time, where
 the overview data block is, offset for the data and the length of data for
 each article.  Each block allocated by block manager is used for one group
 and never shared with other newsgroups. Current overview manager assumes
 all index rooms are allocated for all articles between low and high mark.
 When expiry, overview manager recreate the information into new block by
 checking article existence.  It frees all old blocks and replaces all info
 in group.index for the group.

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Ticket URL: <http://inn-new.eyrie.org/trac/ticket/62>
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