Better documentation to coder param of copy related methods

ext/pg_connection.c

@@ -2560,8 +2560,9 @@ pgconn_wait_for_notify(int argc, VALUE *argv, VALUE self)
  * not sent (false is only possible if the connection
  * is in nonblocking mode, and this command would block).
  *
- * encoder can be a PG::Coder derivation (typically PG::TextEncoder::CopyRow).
- * This encodes the received data fields from an Array of Strings. Optionally
+ * _encoder_ can be a PG::Coder derivation (typically PG::TextEncoder::CopyRow).
+ * This encodes the data fields given as _buffer_ from an Array of Strings to
+ * PostgreSQL's COPY text format inclusive proper escaping. Optionally
  * the encoder can type cast the fields from various Ruby types in one step,
  * if PG::TextEncoder::CopyRow#type_map is set accordingly.
  *
@@ -2673,8 +2674,9 @@ pgconn_put_copy_end(int argc, VALUE *argv, VALUE self)
  * if the copy is done, or +false+ if the call would
  * block (only possible if _async_ is true).
  *
- * decoder can be a PG::Coder derivation (typically PG::TextDecoder::CopyRow).
- * This decodes the received data fields as Array of Strings. Optionally
+ * _decoder_ can be a PG::Coder derivation (typically PG::TextDecoder::CopyRow).
+ * This decodes the received data fields from PostgreSQL's COPY text format to an
+ * Array of Strings. Optionally
  * the decoder can type cast the fields to various Ruby types in one step,
  * if PG::TextDecoder::CopyRow#type_map is set accordingly.
  *

lib/pg/connection.rb

@@ -85,7 +85,7 @@ def self::parse_connect_args( *args )
 
 
 	#  call-seq:
-	#     conn.copy_data( sql ) {|sql_result| ... } -> PG::Result
+	#     conn.copy_data( sql [, coder] ) {|sql_result| ... } -> PG::Result
 	#
 	# Execute a copy process for transfering data to or from the server.
 	#
@@ -109,6 +109,11 @@ def self::parse_connect_args( *args )
 	# of blocking mode of operation, #copy_data is preferred to raw calls
 	# of #put_copy_data, #get_copy_data and #put_copy_end.
 	#
+	# _coder_ can be a PG::Coder derivation
+	# (typically PG::TextEncoder::CopyRow or PG::TextDecoder::CopyRow).
+	# This enables encoding of data fields given to #put_copy_data
+	# or decoding of fields received by #get_copy_data.
+	#
 	# Example with CSV input format:
 	#   conn.exec "create table my_table (a text,b text,c text,d text)"
 	#   conn.copy_data "COPY my_table FROM STDIN CSV" do