Class: PgMeta::Table

Inherits:
Object
  • Object
show all
Defined in:
lib/pg_graph/ext/meta.rb

Instance Method Summary collapse

Instance Method Details

#mm_table? ⇒ Boolean

True if table is a N:M link table. A N:M relation allows for multiple relations between two records

A table is a N:M table if

o it has a primary key named 'id' as the first column
o has two reference fields using the link field naming convention
o and nothing else

Returns:

  • (Boolean) 


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# File 'lib/pg_graph/ext/meta.rb', line 15

def mm_table?
  @mm_table ||= 
      if columns.size != 3
        false
      elsif columns.values.first.name != "id" || columns.values.first != primary_key_column
        false
      else
        referential_constraints.size == 2 &&
        referential_constraints.values.map { |constraint|
          constraint.referencing_columns
        }.sort == [[columns.values[1]], [columns.values[2]]].sort
      end
end

#nm_table? ⇒ Boolean

True if table is a N:N link table. A N:N relation have at most one relation between two records. A N:N link table is also a M:M table

A table is a N:N link table if

o it has a primary key named 'id' as the first column
o has two reference fields using the link field naming convention
o has a unique index on the two reference fields
o and nothing else

Returns:

  • (Boolean) 


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# File 'lib/pg_graph/ext/meta.rb', line 38

def nm_table?
  @nm_table ||= @mm_table && begin
    expected_columns = referential_constraints.values.map(&:columns).flatten.sort
    unique_constraints.values.any? { |constraint|
      expected_columns == constraint.columns.sort
    }
  end
end

#path ⇒ Object 



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# File 'lib/pg_graph/ext/meta.rb', line 47

def path
  schema.name + "." + name
end