June 2001
Intermediate to advanced
688 pages
19h 18m
English
Content preview from Berkeley DB
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Partial Record Storage and Retrieval
It is possible to both store and retrieve parts of data items in all Berkeley DB access methods. This is done by setting the DB_DBT_PARTIAL flag in the DBT structure passed to the Berkeley DB interface.
The DB_DBT_PARTIAL flag is based on the values of two fields of the DBT structure: dlen and doff. The value of dlen is the number of bytes of the record in which the application is interested. The value of doff is the offset from the beginning of the data item where those bytes start.
For example, if the data item were ABCDEFGHIJKL, a doff value of 3 would indicate that the bytes of interest started at D, and a dlen value of 4 would indicate that the bytes of interest were DEFG.
When retrieving a data item ...