Class: ActiveFacts::Metamodel::EntityType

Inherits:
Concept show all
Includes:
ActiveFacts
Defined in:
lib/activefacts/persistence/columns.rb,
lib/activefacts/persistence/tables.rb,
lib/activefacts/vocabulary/metamodel.rb,
lib/activefacts/persistence/reference.rb,
lib/activefacts/vocabulary/extensions.rb

Overview

The EntityType class is defined in the metamodel; full documentation is not generated. This section shows the features relevant to relational Persistence.

Constant Summary

Constants included from ActiveFacts

VERSION

Instance Attribute Summary

Attributes inherited from Concept

#tentative

Instance Method Summary collapse

Methods included from ActiveFacts

extract_hash_args

Methods inherited from Concept

#all_absorbed_foreign_key_reference_path, #clear_indices, #clear_references, #columns, #definitely_not_table, #definitely_table, #foreign_keys, #has_references, #indices, #populate_columns, #populate_indices, #populate_reference, #probably_not_table, #probably_table, #references_from, #references_to, #show_tabular

Instance Method Details

#absorbed_via ⇒ Object

A Reference from an entity type that fully absorbs this one



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# File 'lib/activefacts/persistence/tables.rb', line 60

def absorbed_via; @absorbed_via; end

#absorbed_via=(r) ⇒ Object

:nodoc:



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# File 'lib/activefacts/persistence/tables.rb', line 61

def absorbed_via=(r) #:nodoc:
  @absorbed_via = r
end

#all_columns(excluded_supertypes) ⇒ Object

When absorbing this EntityType, what columns must be absorbed? This must be a fresh copy, because the columns will have References prepended.



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# File 'lib/activefacts/persistence/columns.rb', line 298

def all_columns(excluded_supertypes)    #:nodoc:
  debug :columns, "All Columns for #{name}" do
    columns = []
    sups = supertypes
    references_from.sort_by do |ref|
      # Put supertypes first, in order, then non-subtype references, then subtypes, otherwise retaining their order:
      sups.index(ref.to) ||
        (!ref.fact_type.is_a?(TypeInheritance) && references_from.size+references_from.index(ref)) ||
        references_from.size*2+references_from.index(ref)
    end.each do |ref|
      debug :columns, "Columns absorbed via #{ref}" do
        if (ref.role_type == :supertype)
          if excluded_supertypes[ref.to]
            debug :columns, "Exclude #{ref.to.name}, we already inherited it"
            next
          end

          next if (ref.to.absorbed_via != ref)
          excluded_supertypes[ref.to] = true
          columns += ref.columns(excluded_supertypes)
        else
          columns += ref.columns({})
        end
      end
    end
    columns
  end
end

#all_supertype_inheritance ⇒ Object 



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# File 'lib/activefacts/vocabulary/extensions.rb', line 270

def all_supertype_inheritance
  all_type_inheritance_as_subtype.sort_by{|ti|
      [ti.provides_identification ? 0 : 1, ti.supertype.name]
    }
end

#identifier_columns ⇒ Object

The identifier_columns for an EntityType are the columns that result from the identifying roles



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# File 'lib/activefacts/persistence/columns.rb', line 255

def identifier_columns
  debug :columns, "Identifier Columns for #{name}" do
    if absorbed_via and
      # If this is a subtype that has its own identification, use that.
      (all_type_inheritance_as_subtype.size == 0 ||
        all_type_inheritance_as_subtype.detect{|ti| ti.provides_identification })
      return absorbed_via.from.identifier_columns
    end

    preferred_identifier.role_sequence.all_role_ref.map do |role_ref|
      ref = references_from.detect {|ref| ref.to_role == role_ref.role}

      columns.select{|column| column.references[0] == ref}
    end.flatten
  end
end

#identifying_supertype ⇒ Object

A subtype does not have a identifying_supertype if it defines its own identifier



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# File 'lib/activefacts/vocabulary/extensions.rb', line 292

def identifying_supertype
  debug "Looking for identifying_supertype of #{name}"
  all_type_inheritance_as_subtype.detect{|ti|
      debug "considering supertype #{ti.supertype.name}"
      next unless ti.provides_identification
      debug "found identifying supertype of #{name}, it's #{ti.supertype.name}"
      return ti.supertype
    }
  debug "Failed to find identifying supertype of #{name}"
  return nil
end

#is_auto_assigned ⇒ Object

:nodoc:



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# File 'lib/activefacts/persistence/tables.rb', line 65

def is_auto_assigned  #:nodoc:
  false
end

#is_table ⇒ Object

Returns true if this EntityType is a table



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# File 'lib/activefacts/persistence/tables.rb', line 70

def is_table
  return @is_table if @is_table != nil  # We already make a guess or decision

  @tentative = false

  # Always a table if marked so
  if is_independent
    debug :absorption, "EntityType #{name} is declared independent"
    return @is_table = true
  end

  # Always a table if nowhere else to go, and has no one-to-ones that might flip:
  if references_to.empty? and
      !references_from.detect{|ref| ref.role_type == :one_one }
    debug :absorption, "EntityType #{name} is independent as it has nowhere to go"
    return @is_table = true
  end

  # Subtypes are not a table unless partitioned or separate
  # REVISIT: Support partitioned subtypes here
  if (!supertypes.empty?)
    av = all_supertype_inheritance[0]
    return @is_table = false
  end

  # If the preferred_identifier includes an auto_assigned ValueType
  # and this object is absorbed in more than one place, we need a table
  # to manage the auto-assignment.
  if references_to.size > 1 and
    preferred_identifier.role_sequence.all_role_ref.detect {|rr|
      next false unless rr.role.concept.is_a? ValueType
      rr.role.concept.is_auto_assigned
    }
    debug :absorption, "#{name} has an auto-assigned counter in its ID, so must be a table"
    @tentative = false
    return @is_table = true
  end

  @tentative = true
  @is_table = true
end

#populate_references ⇒ Object

:nodoc:



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# File 'lib/activefacts/persistence/reference.rb', line 319

def populate_references          #:nodoc:
  if fact_type && fact_type.all_role.size > 1
    # NOT: fact_type.all_role.each do |role|  # Place roles in the preferred order instead:
    fact_type.preferred_reading.role_sequence.all_role_ref.map(&:role).each do |role|
      populate_reference role     # Objectified fact role, handled specially
    end
  end
  super
end

#preferred_identifier ⇒ Object 



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# File 'lib/activefacts/vocabulary/extensions.rb', line 123

def preferred_identifier
  if fact_type

    # For a nested fact type, the PI is a unique constraint over N or N-1 roles
    fact_roles = Array(fact_type.all_role)
    debug :pi, "Looking for PI on nested fact type #{name}" do
      pi = catch :pi do
          fact_roles[0,2].each{|r|                  # Try the first two roles of the fact type, that's enough
              r.all_role_ref.map{|rr|               # All role sequences that reference this role
                  role_sequence = rr.role_sequence

                  # The role sequence is only interesting if it cover only this fact's roles
                  # or roles of the objectification
                  next if role_sequence.all_role_ref.size < fact_roles.size-1 # Not enough roles
                  next if role_sequence.all_role_ref.size > fact_roles.size   # Too many roles
                  next if role_sequence.all_role_ref.detect do |rsr|
                      if (of = rsr.role.fact_type) != fact_type
                        case of.all_role.size
                        when 1    # A unary FT must be played by the objectification of this fact type
                          next rsr.role.concept != fact_type.entity_type
                        when 2    # A binary FT must have the objectification of this FT as the other player
                          other_role = (of.all_role-[rsr.role])[0]
                          next other_role.concept != fact_type.entity_type
                        else
                          next true # A role in a ternary (or higher) cannot be usd in our identifier
                        end
                      end
                      rsr.role.fact_type != fact_type
                    end

                  # This role sequence is a candidate
                  pc = role_sequence.all_presence_constraint.detect{|c|
                      c.max_frequency == 1 && c.is_preferred_identifier
                    }
                  throw :pi, pc if pc
                }
            }
          throw :pi, nil
        end
      debug :pi, "Got PI #{pi.name||pi.object_id} for nested #{name}" if pi
      debug :pi, "Looking for PI on entity that nests this fact" unless pi
      raise "Oops, pi for nested fact is #{pi.class}" unless !pi || PresenceConstraint === pi
      return pi if pi
    end
  end

  debug :pi, "Looking for PI for ordinary entity #{name} with #{all_role.size} roles:" do
    debug :pi, "Roles are in fact types #{all_role.map{|r| r.fact_type.describe(r)}*", "}"
    pi = catch :pi do
        all_supertypes = supertypes_transitive
        debug :pi, "PI roles must be played by one of #{all_supertypes.map(&:name)*", "}" if all_supertypes.size > 1
        all_role.each{|role|
            next unless role.unique || fact_type
            ftroles = Array(role.fact_type.all_role)

            # Skip roles in ternary and higher fact types, they're objectified, and in unaries, they can't identify us.
            next if ftroles.size != 2

            debug :pi, "Considering role in #{role.fact_type.describe(role)}"

            # Find the related role which must be included in any PI:
            # Note this works with unary fact types:
            pi_role = ftroles[ftroles[0] != role ? 0 : -1]

            next if ftroles.size == 2 && pi_role.concept == self
            debug :pi, "  Considering #{pi_role.concept.name} as a PI role"

            # If this is an identifying role, the PI is a PC whose role_sequence spans the role.
            # Walk through all role_sequences that span this role, and test each:
            pi_role.all_role_ref.each{|rr|
                role_sequence = rr.role_sequence  # A role sequence that includes a possible role

                debug :pi, "    Considering role sequence #{role_sequence.describe}"

                # All roles in this role_sequence must be in fact types which
                # (apart from that role) only have roles played by the original
                # entity type or a supertype.
                #debug :pi, "      All supertypes #{all_supertypes.map{|st| "#{st.object_id}=>#{st.name}"}*", "}"
                if role_sequence.all_role_ref.detect{|rsr|
                    fact_type = rsr.role.fact_type
                    debug :pi, "      Role Sequence touches #{fact_type.describe(pi_role)}"

                    fact_type_roles = fact_type.all_role
                    debug :pi, "      residual is #{fact_type_roles.map{|r| r.concept.name}.inspect} minus #{rsr.role.concept.name}"
                    residual_roles = fact_type_roles-[rsr.role]
                    residual_roles.detect{|rfr|
                        debug :pi, "        Checking residual role #{rfr.concept.object_id}=>#{rfr.concept.name}"
# This next line looks right, but breaks things. Find out what and why:
#                              !rfr.unique or
                          !all_supertypes.include?(rfr.concept)
                      }
                  }
                  debug :pi, "      Discounting this role_sequence because it includes alien roles"
                  next
                end

                # Any presence constraint over this role sequence is a candidate
                rr.role_sequence.all_presence_constraint.detect{|pc|
                    # Found it!
                    if pc.is_preferred_identifier
                      debug :pi, "found PI #{pc.name||pc.object_id}, is_preferred_identifier=#{pc.is_preferred_identifier.inspect} over #{pc.role_sequence.describe}"
                      throw :pi, pc
                    end
                  }
              }
          }
        throw :pi, nil
      end
    raise "Oops, pi for entity is #{pi.class}" if pi && !(PresenceConstraint === pi)
    debug :pi, "Got PI #{pi.name||pi.object_id} for #{name}" if pi

    if !pi
      if (supertype = identifying_supertype)
        # This shouldn't happen now, as an identifying supertype is connected by a fact type
        # that has a uniqueness constraint marked as the preferred identifier.
        #debug :pi, "PI not found for #{name}, looking in supertype #{supertype.name}"
        #pi = supertype.preferred_identifier
        #return nil
      elsif fact_type
        fact_type.all_role.each{|role|
          role.all_role_ref.each{|role_ref|
            # Discount role sequences that contain roles not in this fact type:
            next if role_ref.role_sequence.all_role_ref.detect{|rr| rr.role.fact_type != fact_type }
            role_ref.role_sequence.all_presence_constraint.each{|pc|
              next unless pc.is_preferred_identifier and pc.max_frequency == 1
              pi = pc
              break
            }
            break if pi
          }
          break if pi
        }
      else
        debug :pi, "No PI found for #{name}"
      end
    end
    raise "No PI found for #{name}" unless pi
    pi
  end
end

#reference_columns(excluded_supertypes) ⇒ Object

When creating a foreign key to this EntityType, what columns must we include (the identifier columns)? This must be a fresh copy, because the columns will have References prepended



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# File 'lib/activefacts/persistence/columns.rb', line 274

def reference_columns(excluded_supertypes)    #:nodoc:
  debug :columns, "Reference Columns for #{name}" do

    if absorbed_via and
      # If this is a subtype that has its own identification, use that.
      (all_type_inheritance_as_subtype.size == 0 ||
        all_type_inheritance_as_subtype.detect{|ti| ti.provides_identification })
      return absorbed_via.from.reference_columns(excluded_supertypes)
    end

    # REVISIT: Should have built preferred_identifier_references
    preferred_identifier.role_sequence.all_role_ref.map do |role_ref|
      # REVISIT: Should index references by to_role:
      ref = references_from.detect {|ref| ref.to_role == role_ref.role}

      raise "reference for role #{role.describe} not found on #{name} in #{references_from.size} references:\n\t#{references_from.map(&:to_s)*"\n\t"}" unless ref

      ref.columns({})
    end.flatten
  end
end

#subtypes ⇒ Object

An array of all direct subtypes:



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# File 'lib/activefacts/vocabulary/extensions.rb', line 265

def subtypes
  # REVISIT: There's no sorting here. Should there be?
  all_type_inheritance_as_supertype.map{|ti| ti.subtype }
end

#supertypes ⇒ Object

An array all direct supertypes



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# File 'lib/activefacts/vocabulary/extensions.rb', line 277

def supertypes
  all_supertype_inheritance.map{|ti|
      ti.supertype
    }
end

#supertypes_transitive ⇒ Object

An array of self followed by all supertypes in order:



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# File 'lib/activefacts/vocabulary/extensions.rb', line 284

def supertypes_transitive
  ([self] + all_type_inheritance_as_subtype.map{|ti|
      # debug ti.class.roles.verbalise; exit
      ti.supertype.supertypes_transitive
    }).flatten.uniq
end