class DB::Database

Overview

Acts as an entry point for database access. Connections are managed by a pool. Use DB#open to create a Database instance.

Refer to QueryMethods and SessionMethods for documentation about querying the database.

Database URI

Connection parameters are configured in a URI. The format is specified by the individual database drivers. See the reference book for examples.

The connection pool can be configured from URI parameters:

When querying a database, prepared statements are used by default. This can be changed from the prepared_statements URI parameter:

Included Modules

Defined in:

db/database.cr

Instance Method Summary

Instance methods inherited from module DB::ConnectionContext

discard(connection : Connection) discard, prepared_statements? : Bool prepared_statements?, release(connection : Connection) release, uri : URI uri

Instance methods inherited from module DB::SessionMethods(DB::Database, DB::PoolStatement)

build(query) : Stmt build, build_unprepared_statement(query) : Stmt build_unprepared_statement, fetch_or_build_prepared_statement(query) : Stmt fetch_or_build_prepared_statement, prepared(query)
prepared prepared, prepared_statements? : Bool prepared_statements?, unprepared(query)
unprepared unprepared

Instance methods inherited from module DB::QueryMethods(DB::PoolStatement)

exec(query, *args_, args : Array | Nil = nil) exec, query(query, *args_, args : Array | Nil = nil)
query(query, *args_, args : Array | Nil = nil, &) query, query_all(query, *args_, args : Array | Nil = nil, &block : ResultSet -> U) : Array(U) forall U
query_all(query, *args_, args : Array | Nil = nil, as types : Tuple)
query_all(query, *args_, args : Array | Nil = nil, as types : NamedTuple)
query_all(query, *args_, args : Array | Nil = nil, as type : Class) query_all, query_each(query, *args_, args : Array | Nil = nil, &) query_each, query_one(query, *args_, args : Array | Nil = nil, &block : ResultSet -> U) : U forall U
query_one(query, *args_, args : Array | Nil = nil, as types : Tuple)
query_one(query, *args_, args : Array | Nil = nil, as types : NamedTuple)
query_one(query, *args_, args : Array | Nil = nil, as type : Class) query_one, query_one?(query, *args_, args : Array | Nil = nil, &block : ResultSet -> U) : U | Nil forall U
query_one?(query, *args_, args : Array | Nil = nil, as types : Tuple)
query_one?(query, *args_, args : Array | Nil = nil, as types : NamedTuple)
query_one?(query, *args_, args : Array | Nil = nil, as type : Class) query_one?, scalar(query, *args_, args : Array | Nil = nil) scalar

Instance Method Detail

def checkout #

returns a connection from the pool the returned connection must be returned to the pool by explictly calling Connection#release


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def close #

Closes all connection to the database.


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def prepared_statements? : Bool #
Description copied from module DB::ConnectionContext

Return whether the statements should be prepared by default


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def setup_connection(&proc : Connection -> Nil) #

Run the specified block every time a new connection is established, yielding the new connection to the block.

db = DB.open(DB_URL)
db.setup_connection do |connection|
  connection.exec "SET TIME ZONE 'America/New_York'"
end

[View source]
def transaction(&) #

yields a Transaction from a connection of the pool Refer to BeginTransaction#transaction for documentation.


[View source]
def uri : URI #

Returns the uri with the connection settings to the database


[View source]
def using_connection(&) #

yields a connection from the pool the connection is returned to the pool when the block ends


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