utility.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: utility.so,v 10.18 2004/10/05 16:44:33 bostic Exp $])

m4_ref_title(Dumping and Reloading,
    The db_dump and db_load utilities,
    dumping/loading @text to/from databases,
    ext/php, dumpload/format)

m4_p([dnl
There are three utilities used for dumping and loading m4_db
databases: m4_ref(db_dump), m4_ref(db_dump185), and m4_ref(db_load).])

m4_p([dnl
The m4_ref(db_dump) and m4_ref(db_dump185) utilities dump m4_db
databases into a flat-text representation of the data that can be read
by m4_ref(db_load).  The only difference between them is that
m4_ref(db_dump) reads m4_db version 2 and greater database formats,
whereas m4_ref(db_dump185) reads m4_db version 1.85 and 1.86 database
formats.])

m4_p([dnl
The m4_ref(db_load) utility reads either the output format used
by the dump utilities or (optionally) a flat-text representation
created using other tools, and stores it into a m4_db database.])

m4_p([dnl
Dumping and reloading Hash databases that use user-defined hash functions
will result in new databases that use the default hash function. Although
using the default hash function may not be optimal for the new database,
it will continue to work correctly.])

m4_p([dnl
Dumping and reloading Btree databases that use user-defined prefix or
comparison functions will result in new databases that use the default
prefix and comparison functions. In this case, it is quite likely that
applications will be unable to retrieve records, and it is possible that
the load process itself will fail.])

m4_p([dnl
The only available workaround for either Hash or Btree databases is to
modify the sources for the m4_ref(db_load) utility to load the database
using the correct hash, prefix, and comparison functions.])

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