curdup.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: curdup.so,v 11.6 2001/03/01 15:57:49 bostic Exp $])

m4_ref_title(Access Methods, Duplicating a cursor,
    [@duplicating a cursor, duplicating a @cursor], am/curdel, am/join)

m4_p([dnl
Once a cursor has been initialized (for example, by a call to
m4_ref(dbc_get)), it can be thought of as identifying a particular
location in a database.  The m4_refT(dbc_dup) permits an application to
create a new cursor that has the same locking and transactional
information as the cursor from which it is copied, and which optionally
refers to the same position in the database.])

m4_p([dnl
In order to maintain a cursor position when an application is using
locking, locks are maintained on behalf of the cursor until the cursor is
closed.  In cases when an application is using locking without
transactions, cursor duplication is often required to avoid
self-deadlocks.  For further details, refer to
m4_link(M4RELDIR/ref/lock/am_conv, Access method locking conventions).])

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