Class: PgKingdom::Table

Inherits:
Object
  • Object
show all
Defined in:
lib/pgkingdom/table.rb

Overview

Class, which represents table in database. Contains information about table schema, name, columns (with types and options), constraints, primary and foreign keys. Also provides methods to generate #create(#create!), #drop(#drop!) SQL statements.

Instance Attribute Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(name, &attr_block) ⇒ Postruby::Table

Defines new Table with a given block.

Raises:

  • (SyntaxError) —

    when block was not given of block is empty.



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# File 'lib/pgkingdom/table.rb', line 20

def initialize(name, &attr_block)
  if attr_block.nil?
    raise SyntaxError.new "Table columns should be given within a block."
  end

  if name.is_a? Array
    @schema = name.first
    @name = name.last
  else
    @schema = :public
    @name = name
  end

  @columns = []
  @columns.extend ColumnsHelper

  instance_eval &attr_block

  unless @columns.any?
    raise SyntaxError.new "Given block should not be empty."
  end
end

Dynamic Method Handling

This class handles dynamic methods through the method_missing method

#method_missing(type, *opts) ⇒ Object

Acts as DSL to define table columns.

Raises:

  • (RuntimeError) —

    when column type is not supported or column was redeclared for current table.



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# File 'lib/pgkingdom/table.rb', line 45

def method_missing(type, *opts)
  unless @columns.available? type
    raise "Unsupported column datatype #{type} for table #{@name}."
  end

  col_name = opts.shift
  if @columns.defined? col_name
    raise "Column #{col_name} with type #{type} has been redeclared for table #{@name}."
  end

  @columns.add col_name, type, opts
end

Instance Attribute Details

#name ⇒ String|Symbol (readonly)

Returns table name.

Returns:

  • (String|Symbol) 


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# File 'lib/pgkingdom/table.rb', line 15

def name
  @name
end

#schema ⇒ String|Symbol (readonly)

Returns schema name.

Returns:

  • (String|Symbol) 


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# File 'lib/pgkingdom/table.rb', line 11

def schema
  @schema
end

Instance Method Details

#column_defined?(name) ⇒ Boolean

Helper, checks if column was defined in Table.

Returns:

  • (Boolean) 


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# File 'lib/pgkingdom/table.rb', line 95

def column_defined?(name) @columns.defined? name end

#column_exists?(name, type = nil) ⇒ String

Generates SQL query to check if column exists in table.

Returns:

  • (String) —

    SQL statement.



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# File 'lib/pgkingdom/table.rb', line 99

def column_exists?(name, type=nil)
  # TODO: write pgSQL query
end

#create(safe = true) ⇒ String

Generates SQL to create table in the database. When safe is true and table already exists it allows to skip this action.

Returns:

  • (String) —

    SQL statement.



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# File 'lib/pgkingdom/table.rb', line 66

def create(safe=true)
  allow_skip = safe ? " IF NOT EXISTS" : ""
  <<~SQL
  CREATE TABLE#{allow_skip} #{table_path} (
    #{@columns.join}
  );
  SQL
end

#create! ⇒ String

Helper, which calls create with safe=false.

Returns:

  • (String) —

    SQL statement.



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# File 'lib/pgkingdom/table.rb', line 87

def create!; create(false) end

#drop(safe = true) ⇒ String

Generates SQL to drop table in the database. When safe is true and table doesn't exist it allows to skip this action.

Returns:

  • (String) —

    SQL statement.



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# File 'lib/pgkingdom/table.rb', line 79

def drop(safe=true)
  <<~SQL
  DROP TABLE#{safe ? " IF EXISTS" : ""} #{table_path};
  SQL
end

#drop! ⇒ String

Helper, which calls drop with safe=false.

Returns:

  • (String) —

    SQL statement.



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# File 'lib/pgkingdom/table.rb', line 91

def drop!; drop(false) end

#table_exists? ⇒ String

Generates SQL to check if table exists in the database.

Returns:

  • (String) —

    SQL statement.



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# File 'lib/pgkingdom/table.rb', line 105

def table_exists?
  "SELECT to_regclass('#{table_path}') IS NOT NULL AS table_exists;"
end

#table_path ⇒ String

Helper, which returns table path ..

Returns:

  • (String) —

    path including schema name and table name.



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# File 'lib/pgkingdom/table.rb', line 60

def table_path; "#{@schema}.#{@name}" end