Acces Methods
These are the common methods for BDB::Btree, BDB::Hash, BDB::Recno and BDB::Queue
Class Methods
open(name = nil, subname = nil, flags = 0, mode = 0, options = {})create(name = nil, subname = nil, flags = 0, mode = 0, options = {})new(name = nil, subname = nil, flags = 0, mode = 0, options = {})-
open the database
- name
-
The argument name is used as the name of a single physical file on disk that will be used to back the database.
- subname
-
The subname argument allows applications to have subdatabases, i.e., multiple databases inside of a single physical file. This is useful when the logical databases are both numerous and reasonably small, in order to avoid creating a large number of underlying files. It is an error to attempt to open a subdatabase in a database file that was not initially created using a subdatabase name.
- flags
-
The flags must be the string "r", "r+", "w", "w+", "a", "a+" or and integer value.
The flags value must be set to 0 or by bitwise inclusively OR'ing together one or more of the following values
- BDB::CREATE
-
Create any underlying files, as necessary. If the files do not already exist and the DB_CREATE flag is not specified, the call will fail.
- BD::EXCL
-
Return an error if the database already exists. Underlying filesystem primitives are used to implement this flag. For this reason it is only applicable to the physical database file and cannot be used to test if a subdatabase already exists.
- BDB::NOMMAP
-
Do not map this database into process memory.
- BDB::RDONLY
-
Open the database for reading only. Any attempt to modify items in the database will fail regardless of the actual permissions of any underlying files.
- BDB::TRUNCATE
-
Physically truncate the underlying database file, discarding all previous subdatabases or databases. Underlying filesystem primitives are used to implement this flag. For this reason it is only applicable to the physical database file and cannot be used to discard subdatabases.
The DB_TRUNCATE flag cannot be transaction protected, and it is an error to specify it in a transaction protected environment.
- options
-
Hash, Possible options are (see the documentation of Berkeley DB for more informations)
- set_array_base: base index for BDB::Recno, BDB::Queue or BDB::Btree (with BDB::RECNUM). Must be 0 or 1
- set_bt_compare : specify a Btree comparison function
- set_bt_minkey : set the minimum number of keys per Btree page
- set_bt_prefix : specify a Btree prefix comparison function
- set_cachesize : set the database cache size
- set_dup_compare : specify a duplicate comparison function
- set_store_key : specify a Proc called before a key is stored
- set_fetch_key : specify a Proc called after a key is read
- set_store_value : specify a Proc called before a value is stored
- set_fetch_value : specify a Proc called after a value is read
- set_flags : general database configuration
- set_h_ffactor : set the Hash table density
- set_h_hash : specify a hashing function
- set_h_nelem : set the Hash table size
- set_lorder : set the database byte order
- set_pagesize : set the underlying database page size
- set_re_delim : set the variable-length record delimiter
- set_re_len : set the fixed-length record length
- set_re_pad : set the fixed-length record pad byte
- set_re_source : set the backing Recno text file
- set_append_recno : modify the stored data for BDB::APPEND
- set_encrypt : set the password used
- set_feedback : set the function to monitor some operations
- env : open the database in the environnement given as the value
- txn : open the database in the transaction given as the value
set_append_recno will be called with (key, value) and it must return nil or the modified value
set_encrypt take an Array as arguments with the values [password, flags], where flags can be 0 or BDB::ENCRYPT_AES
Proc given to set_bt_compare, set_bt_prefix, set_dup_compare, set_h_hash, set_store_key set_fetch_key, set_store_value, set_fetch_value set_feedback and set_append_recno can be also specified as a method (replace the prefix set_ with bdb_)
For example module BDB class Btreesort < Btree def bdb_bt_compare(a, b) b.downcase <=> a.downcase end end end
remove(name, subname = nil)db_remove(name, subname = nil)unlink(name, subname = nil)-
Removes the database (or subdatabase) represented by the name and subname combination.
If no subdatabase is specified, the physical file represented by name is removed, incidentally removing all subdatabases that it contained.
upgrade(name)db_upgrade(name)-
Upgrade the database
Methods
self[key]-
Returns the value corresponding the key
associate(db, flag = 0) { |db, key, value| }-
associate a secondary index db
flag can have the value BDB::RDONLY
The block must return the new key, or Qfalse in this case the secondary index will not contain any reference to key/value
cache_priority-
return the current priority value
cache_priority=value-
set the priority value : can be BDB::PRIORITY_VERY_LOW, BDB::PRIORITY_LOW, BDB::PRIORITY_DEFAULT, BDB::PRIORITY_HIGH or BDB::PRIORITY_VERY_HIGH
feedback=(proc)-
monitor the progress of some operations
get(key, flags = 0)db_get(key, flags = 0)fetch(key, flags = 0)-
Returns the value correspondind the key
flags can have the values BDB::GET_BOTH, BDB::SET_RECNO or BDB::RMW
In presence of duplicates it will return the first data item, use #duplicates if you want all duplicates (see also #each_dup)
pget(key, flags = 0)-
Returns the primary key and the value corresponding to key in the secondary index
only with >= 3.3.11
self[key] = value-
Stores the value associating with key
If nil is given as the value, the association from the key will be removed.
put(key, value, flags = 0)db_put(key, value, flags = 0)store(key, value, flags = 0)-
Stores the value associating with key
If nil is given as the value, the association from the key will be removed. It return the object deleted or nil if the specified key don't exist.
flags can have the value DBD::NOOVERWRITE, in this case it will return nil if the specified key exist, otherwise true
append(key, value)db_append(key, value)-
Append the value associating with key
byteswapped?get_byteswapped-
Return if the underlying database is in host order
clear_partialpartial_clear-
Clear partial set.
close(flags = 0)db_close(flags = 0)-
Closes the file.
count(key)dup_count(key)-
Return the count of duplicate for key
cursor(flags = 0)db_cursor(flags = 0)-
Open a new cursor.
database()subname()-
Return the subname
delete(key)db_del(key)-
Removes the association from the key.
It return the object deleted or nil if the specified key don't exist.
delete_if(set = nil) { |key, value| ... }reject!(set = nil) { |key, value| ... }-
Deletes associations if the evaluation of the block returns true.
duplicates(key , assoc = true)-
Return an array of all duplicate associations for key
if assoc is false return only the values.
each(set = nil, bulk = 0, "flags" => 0) { |key, value| ... }each_pair(set = nil, bulk = 0) { |key, value| ... }-
Iterates over associations.
each_dup(key, bulk = 0) { |key, value| ... }-
Iterates over each duplicate associations for key
each_dup_value(key, bulk = 0) { |value| ... }-
Iterates over each duplicate values for key
each_key(set = nil, bulk = 0) { |key| ... }-
Iterates over keys.
each_primary(set = nil) { |skey, pkey, pvalue| ... }-
Iterates over secondary indexes and give secondary key, primary key and value
each_value(set = nil, bulk = 0) { |value| ... }-
Iterates over values.
empty?()-
Returns true if the database is empty.
filename()-
Return the name of the file
has_key?(key)key?(key)include?(key)member?(key)-
Returns true if the association from the key exists.
has_both?(key, value)both?(key, value)-
Returns true if the association from key is value
has_value?(value)value?(value)-
Returns true if the association to the value exists.
index(value)-
Returns the first key associated with value
indexes(value1, value2, )-
Returns the keys associated with value1, value2, ...
join(cursor , flag = 0) { |key, value| ... }-
Perform a join. cursor is an array of BDB::Cursor
keys-
Returns the array of the keys in the database
lengthsize-
Returns the number of association in the database.
log_register(name)-
The log_register function registers a file name.
log_unregister()-
The log_unregister function unregisters a file name.
reject { |key, value| ... }-
Create an hash without the associations if the evaluation of the block returns true.
reverse_each(set = nil) { |key, value| ... }reverse_each_pair(set = nil) { |key, value| ... }-
Iterates over associations in reverse order
reverse_each_key(set = nil) { |key| ... }-
Iterates over keys in reverse order
reverse_each_primary(set = nil) { |skey, pkey, pvalue| ... }-
Iterates over secondary indexes in reverse order and give secondary key, primary key and value
reverse_each_value(set = nil) { |value| ... }-
Iterates over values in reverse order.
set_partial(len, offset)-
Set the partial value len and offset
stat-
Return database statistics.
to_a-
Return an array of all associations [key, value]
to_hash-
Return an hash of all associations {key => value}
truncateclear-
Empty a database
values-
Returns the array of the values in the database.
verify(file = nil, flags = 0)-
Verify the integrity of the DB file, and optionnally output the key/data to file (file must respond to #to_io)
Methods specific to BDB::Recno and BDB::Queue
pop-
Returns the last couple [key, val] (only for BDB::Recno)
push values-
Push the values
shift-
Removes and returns an association from the database.
Remark
set
If the parameter set is given, an initial call will be made with the option BDB::SET_RANGE to move the cursor to the specified key before iterating.
bulk
Only with >= 3.3.11 : if the parameter bulk is given, an application buffer of size bulk * 1024 will be used (see "Retrieving records in bulk" in the documentation of BerkeleyDB)