class Thingfish::Metastore::PG::Metadata
A row of metadata describing an asset in a Thingfish
store.
Public Class Methods
Return a new Metadata
object from the given oid
and one-dimensional hash
used by Thingfish
.
# File lib/thingfish/metastore/pg/metadata.rb, line 89 def self::from_hash( hash ) metadata = Thingfish::Normalization.normalize_keys( hash ) md = new md.format = metadata.delete( 'format' ) md.extent = metadata.delete( 'extent' ) md.created = metadata.delete( 'created' ) md.uploadaddress = metadata.delete( 'uploadaddress' ).to_s md.user_metadata = Sequel.pg_jsonb( metadata ) return md end
Return the columns of the table that are used for resource metadata.
# File lib/thingfish/metastore/pg/metadata.rb, line 106 def self::metadata_columns return self.columns - [self.primary_key, :user_metadata] end
Do some initial attribute setup for new objects.
# File lib/thingfish/metastore/pg/metadata.rb, line 112 def initialize( * ) super self[ :user_metadata ] ||= Sequel.pg_jsonb({}) end
Public Instance Methods
Merge new metadata values
into the metadata for the resource
# File lib/thingfish/metastore/pg/metadata.rb, line 131 def merge!( values ) # Extract and set the column-metadata values first self.class.metadata_columns.each do |col| next unless values.key?( col.to_s ) self[ col ] = values.delete( col.to_s ) end self.user_metadata.merge!( values ) end
Dataset method: Order results by the specified columns
.
# File lib/thingfish/metastore/pg/metadata.rb, line 59 def order_metadata( *columns ) columns.flatten! ds = self columns.each do |column| if Thingfish::Metastore::PG::Metadata.metadata_columns.include?( column.to_sym ) ds = ds.order_append( column.to_sym ) else ds = ds.order_append( self.user_metadata_expr(column) ) end end return ds end
Return the metadata as a Hash; overridden from Sequel::Model to merge the user and system pairs together.
# File lib/thingfish/metastore/pg/metadata.rb, line 120 def to_hash hash = self.values hash.delete( :oid ) hash.merge!( hash.delete(:user_metadata) ) return normalize_keys( hash ) end
Returns a Sequel expression suitable for use as the key of a query against the specified user metadata field.
# File lib/thingfish/metastore/pg/metadata.rb, line 80 def user_metadata_expr( field ) return Sequel.pg_jsonb( :user_metadata ).get_text( field.to_s ) end
Dataset method: Limit results to records whose operational or user metadata matches the values from the specified hash
.
# File lib/thingfish/metastore/pg/metadata.rb, line 44 def where_metadata( hash ) ds = self hash.each do |field, value| if Thingfish::Metastore::PG::Metadata.metadata_columns.include?( field.to_sym ) ds = ds.where( field.to_sym => value ) else ds = ds.where( self.user_metadata_expr(field) => value ) end end return ds end
Protected Instance Methods
Proxy method – fetch a value from the metadata hash if it exists.
# File lib/thingfish/metastore/pg/metadata.rb, line 148 def method_missing( sym, *args, &block ) return super if sym == :user_metadata return self.user_metadata[ sym.to_s ] || super end