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Berkeley DB: Bulk Retrieval API
Bulk Retrieval API
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#include <db_cxx.h>
class DbMultipleDataIterator
{
public:
DbMultipleDataIterator(const Dbt &dbt);
bool next(Dbt &data);
};
class DbMultipleKeyDataIterator
{
public:
DbMultipleKeyDataIterator(const Dbt &dbt);
bool next(Dbt &key, Dbt &data);
};
class DbMultipleRecnoDataIterator
{
public:
DbMultipleRecnoDataIterator(const Dbt &dbt);
bool next(db_recno_t &key, Dbt &data);
};
Description: Bulk Retrieval API
If either of the DB_MULTIPLE or DB_MULTIPLE_KEY flags
were specified to the Db::get or Dbc::get method, the data
Dbt returned by those interfaces will refer to a buffer that
is filled with data. Access to that data is through the following
classes.
All instances of the bulk retrieval classes may be used only once, and
to traverse the bulk retrieval buffer in the forward direction only.
However, they are nondestructive, so multiple iterators can be
instantiated and used on the same returned data Dbt.
Description: DbMultipleIterator
The DbMultipleIterator is a shared package-private base class
for the three types of bulk-return Iterator; it should never be
instantiated directly, but it handles the functionality shared by its
subclasses.
Description: DbMultipleDataIterator
The DbMultipleDataIterator class is used to iterate through data
returned using the DB_MULTIPLE flag from a database belonging
to any access method.
The constructor takes the data Dbt returned by the call to
Db::get or Dbc::get that used the DB_MULTIPLE
flag.
Parameters
- dbt
- The dbt parameter is a data Dbt returned by the call to
Db::get or Dbc::get that used the DB_MULTIPLE
flag.
Description: DbMultipleDataIterator.next
The DbMultipleDataIterator.next method takes a Dbt that will be
filled in with a reference to a buffer, a size, and an offset that
together yield the next data item in the original bulk retrieval buffer.
The DbMultipleDataIterator.next method returns false if no more data are
available, and true otherwise.
Parameters
- data
- The data parameter is a Dbt that will be filled in with
a reference to a buffer, a size, and an offset that together yield the
next data item in the original bulk retrieval buffer.
Description: DbMultipleKeyDataIterator
The DbMultipleKeyDataIterator class is used to iterate through
data returned using the DB_MULTIPLE_KEY flag from a database
belonging to the Btree or Hash access methods.
The constructor takes the data Dbt returned by the call to
Db::get or Dbc::get that used the DB_MULTIPLE_KEY
flag.
Parameters
- dbt
- The dbt parameter is a data Dbt returned by the call to
Db::get or Dbc::get that used the DB_MULTIPLE_KEY
flag.
Description: DbMultipleKeyDataIterator.next
The DbMultipleKeyDataIterator.next method takes two Dbts, one
for a key and one for a data item, that will each be filled in with a
reference to a buffer, a size, and an offset that together yield the
next key and data item in the original bulk retrieval buffer. The
DbMultipleKeyDataIterator.next method returns false if no more data are
available, and true otherwise.
The DbMultipleKeyDataIterator.next method returns false if no more data
are available, and true otherwise.
Parameters
- key
- The key parameter will be filled in with a reference to a buffer,
a size, and an offset that yields the next key item in the original bulk
retrieval buffer.
- data
- The data parameter will be filled in with a reference to a buffer,
a size, and an offset that yields the next data item in the original bulk
retrieval buffer.
Description: DbMultipleRecnoDataIterator
This class is used to iterate through data returned using the
DB_MULTIPLE_KEY flag from a database belonging to the Recno or
Queue access methods.
The constructor takes the data Dbt returned by the call to
Db::get or Dbc::get that used the DB_MULTIPLE_KEY
flag.
Parameters
- dbt
- The dbt parameter is a data Dbt returned by the call to
Db::get or Dbc::get that used the DB_MULTIPLE_KEY
flag.
Description: DbMultipleRecnoDataIterator.next
The DbMultipleRecnoDataIterator.next method takes a db_recno_t
for the key and a Dbt for a data item, which will be filled in
with a pointer to a buffer and a size. Together they yield the next key
and data item in the original bulk retrieval buffer.
The DbMultipleRecnoDataIterator.next method returns false if no more
data are available, and true otherwise.
Parameters
- key
- The key parameter will be filled in with a reference to a
buffer, a size, and an offset that yields the next key item in the
original bulk retrieval buffer.
- data
- The data parameter will be filled in with a reference to a
buffer, a size, and an offset that yields the next data item in the
original bulk retrieval buffer.
Copyright (c) 1996-2004 Sleepycat Software, Inc. - All rights reserved.
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