class

LMDB::Database

Inherits Iterable / Enumerable / LMDB::Disposable / Reference / Object

A Database is a key-value store, which is part of an Environment.

By default, each key maps to one value. However, a Database can be configured to allow duplicate keys, in which case one key will map to multiple values.

Keys are stored in a sorted order. The order can also be configured upon initialization.

Basic operations on a database are #put, #get and #delete records. One can also iterate through records using a Cursor.

All operations requires an active transaction opened in #environment. If no current transaction is found, operations will fail.

Example:

env = LMDB.new "databasedir"
txn = env.transaction
db = env.database "databasename"
db.put "key1", "value1"
db.put "key2", "value2"
db.get "key1" # => "value1"
txn.commit
env.close

Constructors

new(environment : Environment, transaction : AbstractTransaction, flags : Flag = Flag::None)

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new(environment : Environment, name : String, transaction : AbstractTransaction, flags : Flag = Flag::None)

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Instance methods

==(other : self)

Returns true if this reference is the same as other. Invokes same?.

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[](key)

See #get

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[]=(key, value)

See #put

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[]?(key)

See #get?

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clear

Empty out the database.

This should happen within a Transaction.

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cursor

Create and yields a AbstractCursor to iterate through self, closed when the block goes out of scope.

The created cursor is associated with the current transaction and self. It cannot be used after the database is closed, nor when the transaction has ended. A cursor in a Transaction can be closed before its transaction ends, and will otherwise be closed when its transaction ends. A cursor in a ReadOnlyTransaction must be closed explicitly, before or after its transaction ends. It can be reused with Cursor#renew before finally closing it.

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cursor

ditto

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delete(key : String | Pointer(K) | Slice(K) | Array(K) | StaticArray(K, _)) forall K

Deletes the items associated with the given key from self.

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delete(key : K) forall K

ditto

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do_close

Implementors overrides this method to perform resource cleanup If an exception is raised, the resource will not be marked as closed.