Class: OMF::OML::OmlCsvTable

Inherits:
OmlTable
  • Object
show all
Defined in:
lib/omf_oml/csv_table.rb

Overview

This class represents a table whose content is initially stored in a CSV file.

Instance Attribute Summary

Attributes inherited from OmlTable

#max_size, #name, #offset, #schema

Class Method Summary collapse

Instance Method Summary collapse

Methods inherited from OmlTable

#<<, #add_row, #add_rows, #clear, #data_sources, #describe, #indexed_by, #on_before_row_added, #on_content_changed, #on_row_added, #rows, #to_a

Constructor Details

#initialize(tname, schema, opts = {}, &on_before_row_added) ⇒ OmlCsvTable

tname - Name of table schema - OmlSchema or Array containing [name, type*] for every column in table

Table adds a '__id__' column at the beginning which keeps track of the rows unique id



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# File 'lib/omf_oml/csv_table.rb', line 38

def initialize(tname, schema, opts = {}, &on_before_row_added)
  file_name = opts[:file_name]
  unless File.readable?(file_name)
    raise "Can't read CSV file '#{file_name}'"
  end
  csv_opts = {}
  csv_opts[:headers] = (opts[:has_csv_header] == true) #(opts.delete(:has_csv_header) == true)
  unless csv_opts[:headers]
    raise "Current implementation only works with CSV files which inlcude a schema description in the first line"
  end

  encoding =  opts[:encoding] #opts.delete(:encoding)
  mode =  "rb"
  mode << ":#{encoding}" if encoding
  csv = CSV.open(file_name, mode, csv_opts)

  unless schema = opts[:schema]
    unless csv_opts[:headers]
      raise "No schema given and ':has_csv_header' not set to capture schema from file header"
    end
    first_row = csv.shift.fields # force reading the first row to have the header parsed
    #csv.shift.each do |h, v| puts "#{h} => #{v.class}" end
    schema = csv.headers.map do |c|
      c = c.encode('UTF-8', :invalid => :replace, :undef => :replace, :replace => '?')
      name, type = c.split(':')
      [name.strip, (type || 'string').strip]
    end
  end
  super tname, schema, opts

  if first_row # from getting the CSV header
    first_row.insert(0, @row_id += 1) if @add_index
    @rows = [@schema.cast_row(first_row)]
  end

  # This assumes that CSV reader is setup with proper schema converters
  csv.each do |r|
    # Convert any strange strings into a clean ruby string
    row = r.fields.map do |e|
      e ? e.encode('UTF-8', :invalid => :replace, :undef => :replace, :replace => '?') : nil
    end
    row.insert(0, @row_id += 1) if @add_index
    @rows << @schema.cast_row(row)
  end

end

Class Method Details

.create(tname, file_name, opts = {}, &on_before_row_added) ⇒ Object

Parameters:

  • opts (defaults to: {}) 


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# File 'lib/omf_oml/csv_table.rb', line 22

def self.create(tname, file_name, opts = {}, &on_before_row_added)
  opts[:file_name] = file_name
  self.new(tname, opts[:schema], opts, &on_before_row_added)
end

Instance Method Details

#create_sliced_table(col_name, col_value, table_opts = {}) ⇒ Object

Return a new table which only contains the rows of this table whose value in column ‘col_name’ is equal to ‘col_value’



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# File 'lib/omf_oml/csv_table.rb', line 88

def create_sliced_table(col_name, col_value, table_opts = {})
  sname = "#{@name}_slice_#{Kernel.rand(100000)}"
  st = OmlTable.new(sname, @schema, table_opts)
  index = @schema.index_for_col(col_name)
  first_row = true
  @rows.each do |row|
    if row[index] == col_value
      #row = row[1 .. -1] # remove the row_id
      debug "Add first row '#{row.inspect}'" if first_row
      st.add_row(row)
      first_row = false
    end
  end
  def st.release
    # do nothing
  end

  debug "Created sliced table '#{sname}' from '#{@name}' (rows: #{st.rows.length} from #{@rows.length})"
  st
end