Module: Download

Defined in:
lib/download.rb

Overview

Code that translates scopes into downloadable tab-delimited CSV. Dependant on Postgresql.

Class Method Summary (collapse)

Class Method Details

+ (CSV::Table) delete_columns(tbl, columns = [])

Returns delete the specified columns

Parameters:

  • table (CSV::Table)
  • columns (Array) (defaults to: [])

Returns:

  • (CSV::Table)

    delete the specified columns



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# File 'lib/download.rb', line 43

def self.delete_columns(tbl, columns = [])
  return tbl if columns.empty?
  columns.each do |col|
    tbl.delete(col.to_s)
  end
 tbl 
end

+ (Object) generate_csv(scope, exclude_columns: [], header_converters: [], trim_rows: false, trim_columns: false)

translate a scope into a CSV table, with optional tweaks to the data

This is a very nice reference for future consideration:

http://collectiveidea.com/blog/archives/2015/03/05/optimizing-rails-for-memory-usage-part-3-pluck-and-database-laziness


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# File 'lib/download.rb', line 13

def self.generate_csv(scope, exclude_columns: [], header_converters: [], trim_rows: false, trim_columns: false)

  # Check to see if keys is deterministicly ordered
  column_names = scope.columns_hash.keys
 
  h = CSV.new(column_names.join(','), header_converters: header_converters, headers: true)
  h.read
  
  headers = CSV::Row.new(h.headers, h.headers, true)

  tbl = CSV::Table.new([headers])
 
  # Pluck rows is from postgresql_cursor gem  
  scope.pluck_rows(*column_names).each do |o|
    tbl << o.collect{|v| Utilities::Strings.sanitize_for_csv(v) }
    # If keys are not deterministic: .attributes.values_at(*column_names).collect{|v| Utilities::Strings.sanitize_for_csv(v) }
  end

  Download.delete_columns(tbl, exclude_columns) if !exclude_columns.empty?
  Download.trim_columns(tbl) if trim_columns
  Download.trim_rows(tbl) if trim_rows

  # CSV::Converters are only available on read, not generate, so we can't use them here.
  tbl.to_csv(col_sep: "\t", encoding: Encoding::UTF_8)
end

+ (CSV::Table) trim_columns(table)

Parameters:

  • table (CSV::Table)

    remove columns without any non-#blank? values (of course doing this in the scope is better!)

Returns:

  • (CSV::Table)


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# File 'lib/download.rb', line 73

def self.trim_columns(table)
  table.by_col!.delete_if do |h, col|
    d = true
    col.shift
    col.each do |v|
      next if v.blank?
      d = false
      break
    end
    d
  end
  table 
end

+ (CSV::Table) trim_rows(table, skip_id = true)

Parameters:

  • table (CSV::Table)
  • skip_id (Boolean) (defaults to: true)

    if true ignore the 'id'l column in consideration of whether to delete this row delete rows if there are no values in any cell (of course doing this in the scope is better!)

Returns:

  • (CSV::Table)


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# File 'lib/download.rb', line 55

def self.trim_rows(table, skip_id = true)
  headers = table.headers 
  headers = headers - ['id'] if skip_id
  table.by_row!.delete_if do |row|
    d = true
    headers.each do |h|
      next if row[h].blank?
      d = false
      break
    end
    d
  end
  table  
end