Class Sequel::Database

Runs the supplied SQL statement string on the database server. Alias for run.

Returns a dataset from the database. If the first argument is a string, the method acts as an alias for Database#fetch, returning a dataset for arbitrary SQL:

  DB['SELECT * FROM items WHERE name = ?', my_name].all

Otherwise, acts as an alias for Database#from, setting the primary table for the dataset:

  DB[:items].sql #=> "SELECT * FROM items"

Adds a column to the specified table. This method expects a column name, a datatype and optionally a hash with additional constraints and options:

  DB.add_column :items, :name, :text, :unique => true, :null => false
  DB.add_column :items, :category, :text, :default => 'ruby'

See alter_table.

Adds an index to a table for the given columns:

  DB.add_index :posts, :title
  DB.add_index :posts, [:author, :title], :unique => true

Options:

• :ignore_errors - Ignore any DatabaseErrors that are raised

See alter_table.

Dynamically add new servers or modify server options at runtime. Also adds new servers to the connection pool. Intended for use with master/slave or shard configurations where it is useful to add new server hosts at runtime.

servers argument should be a hash with server name symbol keys and hash or proc values. If a servers key is already in use, it’s value is overridden with the value provided.

 DB.add_servers(:f=>{:host=>"hash_host_f"})

Alters the given table with the specified block. Example:

  DB.alter_table :items do
    add_column :category, :text, :default => 'ruby'
    drop_column :category
    rename_column :cntr, :counter
    set_column_type :value, :float
    set_column_default :value, :float
    add_index [:group, :category]
    drop_index [:group, :category]
  end

Note that add_column accepts all the options available for column definitions using create_table, and add_index accepts all the options available for index definition.

See Schema::AlterTableGenerator.

Call the prepared statement with the given name with the given hash of arguments.

Cast the given type to a literal type

Connects to the database. This method should be overridden by descendants.

Creates a view, replacing it if it already exists:

  DB.create_or_replace_view(:cheap_items, "SELECT * FROM items WHERE price < 100")
  DB.create_or_replace_view(:ruby_items, DB[:items].filter(:category => 'ruby'))

Creates a table with the columns given in the provided block:

  DB.create_table :posts do
    primary_key :id
    column :title, :text
    String :content
    index :title
  end

Options:

• :temp - Create the table as a temporary table.
• :ignore_index_errors - Ignore any errors when creating indexes.

See Schema::Generator.

Forcibly creates a table, attempting to drop it unconditionally (and catching any errors), then creating it.

Creates the table unless the table already exists

Creates a view based on a dataset or an SQL string:

  DB.create_view(:cheap_items, "SELECT * FROM items WHERE price < 100")
  DB.create_view(:ruby_items, DB[:items].filter(:category => 'ruby'))

The database type for this database object, the same as the adapter scheme by default. Should be overridden in adapters (especially shared adapters) to be the correct type, so that even if two separate Database objects are using different adapters you can tell that they are using the same database type. Even better, you can tell that two Database objects that are using the same adapter are connecting to different database types (think JDBC or DataObjects).

Returns a blank dataset for this database

Disconnects all available connections from the connection pool. Any connections currently in use will not be disconnected. Options:

• :servers - Should be a symbol specifing the server to disconnect from, or an array of symbols to specify multiple servers.

Removes a column from the specified table:

  DB.drop_column :items, :category

See alter_table.

Removes an index for the given table and column/s:

  DB.drop_index :posts, :title
  DB.drop_index :posts, [:author, :title]

See alter_table.

Drops one or more tables corresponding to the given names:

  DB.drop_table(:posts, :comments)

Drops one or more views corresponding to the given names:

  DB.drop_view(:cheap_items)

Yield a new database object for every server in the connection pool. Intended for use in sharded environments where there is a need to make schema modifications (DDL queries) on each shard.

  DB.each_server{|db| db.create_table(:users){primary_key :id; String :name}}

Executes the given SQL on the database. This method should be overridden in descendants. This method should not be called directly by user code.

Method that should be used when submitting any DDL (Data Definition Language) SQL. By default, calls execute_dui. This method should not be called directly by user code.

Method that should be used when issuing a DELETE, UPDATE, or INSERT statement. By default, calls execute. This method should not be called directly by user code.

Method that should be used when issuing a INSERT statement. By default, calls execute_dui. This method should not be called directly by user code.

Fetches records for an arbitrary SQL statement. If a block is given, it is used to iterate over the records:

  DB.fetch('SELECT * FROM items'){|r| p r}

The method returns a dataset instance:

  DB.fetch('SELECT * FROM items').all

Fetch can also perform parameterized queries for protection against SQL injection:

  DB.fetch('SELECT * FROM items WHERE name = ?', my_name).all

Returns a new dataset with the from method invoked. If a block is given, it is used as a filter on the dataset.

Returns a single value from the database, e.g.:

  # SELECT 1
  DB.get(1) #=> 1

  # SELECT version()
  DB.get(:version.sql_function) #=> ...

The method to call on identifiers going into the database

Set the method to call on identifiers going into the database

The method to call on identifiers coming from the database

Set the method to call on identifiers coming from the database

Returns a string representation of the database object including the class name and the connection URI (or the opts if the URI cannot be constructed).

Proxy the literal call to the dataset, used for default values.

Log a message at level info to all loggers. All SQL logging goes through this method.

Remove any existing loggers and just use the given logger.

Whether to quote identifiers (columns and tables) for this database

Returns true if the database quotes identifiers.

Dynamically remove existing servers from the connection pool. Intended for use with master/slave or shard configurations where it is useful to remove existing server hosts at runtime.

servers should be symbols or arrays of symbols. If a nonexistent server is specified, it is ignored. If no servers have been specified for this database, no changes are made. If you attempt to remove the :default server, an error will be raised.

  DB.remove_servers(:f1, :f2)

Renames a column in the specified table. This method expects the current column name and the new column name:

  DB.rename_column :items, :cntr, :counter

See alter_table.

Renames a table:

  DB.tables #=> [:items]
  DB.rename_table :items, :old_items
  DB.tables #=> [:old_items]

Runs the supplied SQL statement string on the database server. Returns nil. Options:

• :server - The server to run the SQL on.

Parse the schema from the database. Returns the schema for the given table as an array with all members being arrays of length 2, the first member being the column name, and the second member being a hash of column information. Available options are:

• :reload - Get fresh information from the database, instead of using cached information. If table_name is blank, :reload should be used unless you are sure that schema has not been called before with a table_name, otherwise you may only getting the schemas for tables that have been requested explicitly.
• :schema - An explicit schema to use. It may also be implicitly provided via the table name.

Returns a new dataset with the select method invoked.

Default serial primary key options.

An array of servers/shards for this Database object.

Sets the default value for the given column in the given table:

  DB.set_column_default :items, :category, 'perl!'

See alter_table.

Set the data type for the given column in the given table:

  DB.set_column_type :items, :price, :float

See alter_table.

Returns true if the database is using a single-threaded connection pool.

Whether the database and adapter support savepoints, false by default

Acquires a database connection, yielding it to the passed block.

Returns true if a table with the given name exists. This requires a query to the database.

Attempts to acquire a database connection. Returns true if successful. Will probably raise an error if unsuccessful.

Starts a database transaction. When a database transaction is used, either all statements are successful or none of the statements are successful. Note that MySQL MyISAM tabels do not support transactions.

The following options are respected:

• :server - The server to use for the transaction
• :savepoint - Whether to create a new savepoint for this transaction, only respected if the database adapter supports savepoints. By default Sequel will reuse an existing transaction, so if you want to use a savepoint you must use this option.

Typecast the value to the given column_type. Calls typecast_value_#{column_type} if the method exists, otherwise returns the value. This method should raise Sequel::InvalidValue if assigned value is invalid.

Returns the URI identifying the database. This method can raise an error if the database used options instead of a connection string.

Explicit alias of uri for easier subclassing.