renumber.so

berkeley db 4.6.21的源码。berkeley db是一个简单的数据库管理系统

m4_comment([$Id: renumber.so,v 1.4 2001/05/05 01:49:34 bostic Exp $])

m4_ref_title(Upgrading m4_db Applications,
    Release 3.2: Logically renumbering records,,
    upgrade.3.2/callback, upgrade.3.2/incomplete)

m4_p([dnl
In the m4_db 3.2 release, cursor adjustment semantics changed for Recno
databases with mutable record numbers.  Before the 3.2 release, cursors
were adjusted to point to the previous or next record at the time the
record to which the cursor referred was deleted.  This could lead to
unexpected behaviors.  For example, two cursors referring to sequential
records that were both deleted would lose their relationship to each
other and would refer to the same position in the database instead of
their original sequential relationship.  There were also command
sequences that would have unexpected results.  For example, DB_AFTER
and DB_BEFORE cursor put operations, using a cursor previously used to
delete an item, would perform the put relative to the cursor's adjusted
position and not its original position.])

m4_p([dnl
In the m4_db 3.2 release, cursors maintain their position in the tree
regardless of deletion operations using the cursor.  Applications that
perform database operations, using cursors previously used to delete
entries in Recno databases with mutable record numbers, should be
evaluated to ensure that the new semantics do not cause application
failure.])

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