Class: Automodel::SchemaInspector

Inherits:
Object
  • Object
show all
Defined in:
lib/automodel/schema_inspector.rb

Overview

A utility object that issues the actual database inspection commands and returns the table, column, primary-key, and foreign-key data.

Class Method Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(connection_handler) ⇒ SchemaInspector

Returns a new instance of SchemaInspector

Parameters:

  • connection_handler (ActiveRecord::ConnectionHandling) —

    The connection pool/handler (an object that implements ActiveRecord::ConnectionHandling) to inspect and map out.



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# File 'lib/automodel/schema_inspector.rb', line 64

def initialize(connection_handler)
  @connection = connection_handler.connection
  adapter = connection_handler.connection_pool.spec.config[:adapter]

  @registration = known_adapters[adapter.to_sym] || {}
end

Class Method Details

.known_adapters ⇒ Object 



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# File 'lib/automodel/schema_inspector.rb', line 18

def self.known_adapters; @known_adapters; end

.register_adapter(adapter:, tables:, columns:, primary_key:, foreign_keys: nil) ⇒ Object

“Registers” an adapter with the Automodel::SchemaInspector. This allows for alternate mechanisms of procuring lists of tables, columns, primary keys, and/or foreign keys from an adapter that may not itself support #tables/#columns/#primary_key/#foreign_keys.

Parameters:

  • adapter (String, Symbol) —

    The “adapter” value used to match that given in the connection spec. It is with this value that the adapter being registered is matched to an existing database pool/connection.

  • tables (Proc) —

    The Proc to #call to request a list of table names. The Proc will be called with one parameter: a database connection.

  • columns (Proc) —

    The Proc to #call to request a list of columns for a specific table. The Proc will be called with two parameters: a database connection and a table name.

  • primary_key (Proc) —

    The Proc to #call to request the primary key for a specific table. The Proc will be called with two parameters: a database connection and a table name.

  • foreign_keys (Proc) —

    The Proc to #call to request a list of foreign keys for a specific table. The Proc will be called with two parameters: a database connection and a table name.

Raises:



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# File 'lib/automodel/schema_inspector.rb', line 50

def self.register_adapter(adapter:, tables:, columns:, primary_key:, foreign_keys: nil)
  adapter = adapter.to_sym.downcase
  raise Automodel::AdapterAlreadyRegisteredError, adapter if known_adapters.key? adapter

  known_adapters[adapter] = { tables: tables,
                              columns: columns,
                              primary_key: primary_key,
                              foreign_keys: foreign_keys }
end

Instance Method Details

#columns(table_name) ⇒ Array<ActiveRecord::ConnectionAdapters::Column>

Returns a list of columns for the given table.

If a matching Automodel::SchemaInspector registration is found for the connection's adapter, and that registration specified a :columns Proc, the Proc is called. Otherwise, the standard connection #columns is returned.

Parameters:

  • table_name (String) —

    The table whose columns should be fetched.

Returns:

  • (Array<ActiveRecord::ConnectionAdapters::Column>) 


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# File 'lib/automodel/schema_inspector.rb', line 101

def columns(table_name)
  table_name = table_name.to_s

  @columns ||= {}
  @columns[table_name] ||= if @registration[:columns].present?
                             @registration[:columns].call(@connection, table_name)
                           else
                             @connection.columns(table_name)
                           end
end

#foreign_keys(table_name) ⇒ Array<ActiveRecord::ConnectionAdapters::ForeignKeyDefinition>

Returns a list of foreign keys for the given table.

If a matching Automodel::SchemaInspector registration is found for the connection's adapter, and that registration specified a :foreign_keys Proc, the Proc is called. Otherwise, the standard connection #foreign_keys is attempted. If that call to `#foreign_keys raises a ::NoMethodError or ::NotImplementedError, a best-effort attempt is made to build a list of foreign keys based on table and column names.

Parameters:

  • table_name (String) —

    The table whose foreign keys should be fetched.

Returns:

  • (Array<ActiveRecord::ConnectionAdapters::ForeignKeyDefinition>) 


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# File 'lib/automodel/schema_inspector.rb', line 151

def foreign_keys(table_name)
  table_name = table_name.to_s

  @foreign_keys ||= {}
  @foreign_keys[table_name] ||= begin
    if @registration[:foreign_keys].present?
      @registration[:foreign_keys].call(@connection, table_name)
    else
      begin
        @connection.foreign_keys(table_name)
      rescue ::NoMethodError, ::NotImplementedError
        ## Not all ActiveRecord adapters support `#foreign_keys`. When this happens, we'll make
        ## a best-effort attempt to intuit relationships from the table and column names.
        ##
        columns(table_name).map do |column|
          id_pattern = %r{(?:_id|Id)$}
          next unless column.name =~ id_pattern

          target_table = column.name.sub(id_pattern, '')
          next unless target_table.in? tables

          target_column = primary_key(qualified_name(target_table, context: table_name))
          next unless target_column.in? ['id', 'Id', 'ID', column.name]

          ActiveRecord::ConnectionAdapters::ForeignKeyDefinition.new(
            table_name.split('.').last,
            target_table,
            name: "FK_#{SecureRandom.uuid.delete('-')}",
            column:  column.name,
            primary_key: target_column,
            on_update: nil,
            on_delete: nil
          )
        end.compact
      end
    end
  end
end

#known_adapters ⇒ Object 



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# File 'lib/automodel/schema_inspector.rb', line 19

def known_adapters; self.class.known_adapters; end

#primary_key(table_name) ⇒ String+

Returns the primary key for the given table.

If a matching Automodel::SchemaInspector registration is found for the connection's adapter, and that registration specified a :primary_key Proc, the Proc is called. Otherwise, the standard connection #primary_key is returned.

Parameters:

  • table_name (String) —

    The table whose primary key should be fetched.

Returns:

  • (String, Array<String>) 


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# File 'lib/automodel/schema_inspector.rb', line 125

def primary_key(table_name)
  table_name = table_name.to_s

  @primary_keys ||= {}
  @primary_keys[table_name] ||= if @registration[:primary_key].present?
                                  @registration[:primary_key].call(@connection, table_name)
                                else
                                  @connection.primary_key(table_name)
                                end
end

#tables ⇒ Array<String>

Returns a list of table names in the target database.

If a matching Automodel::SchemaInspector registration is found for the connection's adapter, and that registration specified a :tables Proc, the Proc is called. Otherwise, the standard connection #tables is returned.

Returns:

  • (Array<String>) 


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# File 'lib/automodel/schema_inspector.rb', line 80

def tables
  @tables ||= if @registration[:tables].present?
                @registration[:tables].call(@connection)
              else
                @connection.tables
              end
end