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@eric
Created March 16, 2012 20:41
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Use Arel in Rails 2.3
>> engine = ArelBack::Engine.new(ar.connection, Arel::Visitors::MySQL)
>> table = Arel::Table.new(ar.table_name, engine)
>> table.project(Arel.sql('*')).to_sql
=> "SELECT * FROM `awesome_table` "
>>
module ArelBack
class Connection
delegate :primary_key, :table_exists?, :columns, :quote_table_name, :quote_column_name, :quote, :to => :@raw_connection
attr_reader :visitor
def initialize(raw_connection, visitor_klass)
@raw_connection = raw_connection
@visitor = visitor_klass.new(self)
end
def schema_cache
ArelBack::SchemaCache.new(self)
end
end
end
module ArelBack
class Engine
attr_reader :connection
def initialize(raw_connection, visitor_klass)
@raw_connection = raw_connection
@connection = ArelBack::Connection.new(@raw_connection, visitor_klass)
end
end
end
module ArelBack
class SchemaCache
attr_reader :columns, :columns_hash, :primary_keys, :tables
attr_reader :connection
def initialize(conn)
@connection = conn
@tables = {}
@columns = Hash.new do |h, table_name|
h[table_name] = conn.columns(table_name, "#{table_name} Columns")
end
@columns_hash = Hash.new do |h, table_name|
h[table_name] = Hash[columns[table_name].map { |col|
[col.name, col]
}]
end
@primary_keys = Hash.new do |h, table_name|
h[table_name] = table_exists?(table_name) ? conn.primary_key(table_name) : nil
end
end
# A cached lookup for table existence.
def table_exists?(name)
return @tables[name] if @tables.key? name
@tables[name] = connection.table_exists?(name)
end
# Clears out internal caches
def clear!
@columns.clear
@columns_hash.clear
@primary_keys.clear
@tables.clear
end
# Clear out internal caches for table with +table_name+.
def clear_table_cache!(table_name)
@columns.delete table_name
@columns_hash.delete table_name
@primary_keys.delete table_name
@tables.delete table_name
end
end
end
@rtomayko
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Fuck yes son.

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