Class: Vertica::RowDescription

Inherits:
Object
  • Object
show all
Includes:
Enumerable
Defined in:
lib/vertica/row_description.rb

Overview

Class that describes the shape of a query result. It contains an ordered list of Column instances, which describes the columns that will apear for every Row part of the result of a query.

See Also:

Class Method Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(columns) ⇒ RowDescription

Returns a new instance of RowDescription.

Parameters:

  • columns (Array<Vertica::Column>) —

    The list of columns as they will appear in the rows of a query result.

See Also:



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# File 'lib/vertica/row_description.rb', line 33

def initialize(columns)
  @columns = columns
end

Class Method Details

.build(columns) ⇒ Vertica::RowDescription

Builds a new Vertica::RowDescription instance given a list of columns.

Parameters:

Returns:

Raises:

  • (ArgumentError) —

    If no Vertica::RowDescription could be constructed given the provided argument.



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# File 'lib/vertica/row_description.rb', line 15

def self.build(columns)
  case columns
  when Vertica::Protocol::RowDescription
    new(columns.fields.map { |fd| Vertica::Column.build(fd) })
  when Vertica::RowDescription
    columns
  when Array
    new(columns)
  when nil
    nil
  else
    raise ArgumentError, "Invalid list of columns: #{columns.inspect}"
  end
end

Instance Method Details

#build_row(values) ⇒ Vertica::Row

Builds a Vertica::Row instance given a list of values that conforms to this row description.

Parameters:

  • values (Array, Hash, Vertica::Protocol::DataRow) —

    A list of values. The number of values should match the number of columns in the row description.

Returns:

Raises:

  • (ArgumentError) —

    An ArgumentErrpr is raised if the number of values does not match the row description, or if a type is provided that it cannot handle.



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# File 'lib/vertica/row_description.rb', line 98

def build_row(values)
  case values
  when Vertica::Row
    raise ArgumentError, "Row description of provided row does match this row description" if values.row_description != self
    values

  when Vertica::Protocol::DataRow
    raise ArgumentError, "Number of values does not match row description" if values.values.size != size
    converted_values = @columns.map.with_index do |column, index|
      column.data_type.deserialize(values.values.fetch(index))
    end
    Vertica::Row.new(self, converted_values)

  when Array
    raise ArgumentError, "Number of values does not match row description" if values.size != size
    Vertica::Row.new(self, values)

  when Hash
    raise ArgumentError, "Number of values does not match row description" if values.size != size
    values_as_array = @columns.map { |column| values[column.name] || values[column.name.to_sym] }
    Vertica::Row.new(self, values_as_array)

  else
    raise ArgumentError, "Don't know how to build a row from a #{values.class.name} instance"
  end
end

#column(name_or_index) ⇒ Vertica::Column Also known as: []

Returns a column in this row description.

Parameters:

  • name_or_index (String, Symbol, Integer) —

    The name of the column, or the index of the column in this row description.

Returns:

Raises:

  • (KeyError) —

    if the column could not be found in this row description.



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# File 'lib/vertica/row_description.rb', line 42

def column(name_or_index)
  column_with_index(name_or_index).first
end

#column_with_index(name_or_index) ⇒ Array<Vertica::Column, Integer>

Returns a column, accompanied by the index of that column in this row description.

Parameters:

  • name_or_index (String, Symbol, Integer) —

    The name of the column, or the index of the column in this row description.

Returns:

Raises:

  • (KeyError) —

    if the column could not be found in this row description.



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# File 'lib/vertica/row_description.rb', line 53

def column_with_index(name_or_index)
  columns_index.fetch(name_or_index)
end

#each {|column| ... }

This method returns an undefined value.

Iterates over the columns in this row description.

Yields:

  • The provided block will be called with every column.

Yield Parameters:



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# File 'lib/vertica/row_description.rb', line 61

def each(&block)
  @columns.each(&block)
end

#eql?(other) ⇒ Boolean Also known as: ==

Returns true iff this record is equal to the other provided object

Returns:

  • (Boolean) —

    Returns true iff this record is equal to the other provided object



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# File 'lib/vertica/row_description.rb', line 126

def eql?(other)
  self.class === other && other.to_a == self.to_a
end

#hash ⇒ Integer

Returns a hash digtest of this object.

Returns:

  • (Integer) —

    Returns a hash digtest of this object.



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# File 'lib/vertica/row_description.rb', line 133

def hash
  @columns.hash
end

#inspect ⇒ String

Returns a user-consumable string representation of this row description.

Returns:

  • (String) —

    Returns a user-consumable string representation of this row description.



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# File 'lib/vertica/row_description.rb', line 138

def inspect
  "#<#{self.class.name}[#{@columns.map(&:name).join(', ')}]>"
end

#size ⇒ Integer Also known as: length

Returns the number of columns in this row description.

Returns:

  • (Integer) —

    Returns the number of columns in this row description.



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# File 'lib/vertica/row_description.rb', line 66

def size
  @columns.size
end

#to_a ⇒ Array<Vertica::Column>

Returns the columns of this row description as an array.

Returns:

  • (Array<Vertica::Column>) —

    Returns the columns of this row description as an array.



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# File 'lib/vertica/row_description.rb', line 73

def to_a
  @columns.clone
end

#to_h(symbolize_keys: false) ⇒ Hash

Returns the columns of this row description as a hash, index by the column name.

Parameters:

  • symbolize_keys (Boolean) (defaults to: false) —

    Whether to use symbols instead of strings as keys.

Returns:

  • (Hash) —

    Returns the columns of this row description as a hash, index by the column name.

Raises:



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# File 'lib/vertica/row_description.rb', line 82

def to_h(symbolize_keys: false)
  @columns.inject({}) do |carry, column|
    key = symbolize_keys ? column.name.to_sym : column.name
    raise Vertica::Error::DuplicateColumnName, "Column with name #{key} occurs more than once in this row description." if carry.key?(key)
    carry[key] = column
    carry
  end
end