Sha256: 975d6e6ca3a7516bfa872832a6b86200ad8cbe41cb05ca8d23d95d039def26c9
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Size: 1.44 KB
Versions: 5
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Stored size: 1.44 KB
Contents
require 'set'
module Chicago
module ETL
# An end point to write rows.
#
# @abstract
# @api public
class Sink
# Returns the column names expected to be written to this sink.
# @api public
attr_reader :column_names
# @abstract
def initialize(output, column_names, unique_row_key=nil)
@output = output
@column_names = column_names
@written_rows = Set.new
@unique_row_key = unique_row_key
end
# Writes a row to the output.
#
# Row will not be written to the output if it has already been
# written, as identified by the unique row key.
#
# Should not be overridden by subclasses - overwrite write instead.
def <<(row)
unless written?(row)
write row
@written_rows << row[@unique_row_key]
end
end
# Flushes any remaining writes to the output.
#
# By default does nothing, subclasses should override where
# necessary.
def flush
end
# Returns true if this row has previously been written to the
# output.
#
# Always returns false if no key to determine row uniqueness has
# been provided.
def written?(row)
return false if @unique_row_key.nil?
@written_rows.include?(row[@unique_row_key])
end
protected
attr_reader :output
# @abstract
def write(row)
end
end
end
end
Version data entries
5 entries across 5 versions & 1 rubygems