Chapter 6. Db_multimap
This class is the combination of std::multimap and hash_multimap.
By setting database handles as DB_BTREE or DB_HASH type respectively, you will be using an equivalent of std::multimap or hash_multimap respectively. Database(dbp) and environment(penv) handle requirement: The dbp handle must meet the following requirement: 1. Database type should be DB_BTREE or DB_HASH. 2. Either DB_DUP or DB_DUPSORT flag must be set. Note that so far Berkeley DB does not allow DB_DUPSORT be set and the database is storing identical key/data pairs, i.e. we can't store two (1, 2), (1, 2) pairs into a database D with DB_DUPSORT flag set, but only can do so with DB_DUP flag set; But we can store a (1, 2) pair and a (1, 3) pair into D with DB_DUPSORT flag set. So if your data set allows DB_DUPSORT flag, you should set it to gain a lot of performance promotion. 3. No DB_RECNUM flag set. 4. No DB_TRUNCATE specified in database open flags. 5. DB_THREAD must be set if you are sharing the database handle across multiple threads directly, or indirectly by sharing the container object across multiple threads.
See Also
Class Template Parameters
kdt
The key data type.
ddt
The data data type. db_multimap stores key/data pairs.
value_type_sub
Do not specify anything if ddt type is a class/struct type; Otherwise, specify ElementHolder<ddt> to it.
iterator_t
Never specify anything to this type parameter. It is only used internally.
Public Members
| Member | Description |
|---|---|
| insert | Range insertion. |
| erase | Erase elements by key. |
| equal_range | Find the range within which all keys equal to specified key x. |
| equal_range_N | Find equal range and number of key/data pairs in the range. |
| count | Count the number of key/data pairs having specified key x. |
| upper_bound | Find the least key greater than x. |
| db_multimap | Constructor. |
| ~db_multimap | |
| operator= | Container content assignment operator. |
| swap | Swap content with another multimap container. |
| operator== | Returns whether the two containers have identical content. |
| operator!= | Container unequality comparison operator. |
Group
insert
Function Details
void insert(InputIterator first,
InputIterator last)
Range insertion.
Insert a range [first, last) of key/data pairs into this container.
Parameters
last
The open boundary of the range.
first
The closed boundary of the range.
void insert(const_iterator &first,
const_iterator &last)
Range insertion.
Insert a range [first, last) of key/data pairs into this container.
Parameters
last
The open boundary of the range.
first
The closed boundary of the range.
iterator insert(const value_type &x)
Insert a single key/data pair if the key is not in the container.
Parameters
x
The key/data pair to insert.
Return Value
A pair P, if insert OK, i.e. the inserted key wasn't in the container, P.first will be the iterator sitting on the inserted key/data pair, and P.second is true; otherwise P.first is an invalid iterator and P.second is false.
Group: Insert Functions
http://www.cplusplus.com/reference/stl/multimap/insert/