Fixed bug #29294.

The `SELECT 'r' INTO OUTFILE ... FIELDS ENCLOSED BY 'r' ' statement
encoded the 'r' string to a 4 byte string of value x'725c7272'
(sequence of 4 characters: r\rr).
The LOAD DATA statement decoded this string to a 1 byte string of
value x'0d' (ASCII Carriage Return character) instead of the original
'r' character.
The same error also happened with the FIELDS ENCLOSED BY clause
followed by special characters: 'n', 't', 'r', 'b', '0', 'Z' and 'N'.

NOTE 1: This is a result of the undocumented feature: the LOAD DATA INFILE
recognises 2-byte input sequences like \n, \t, \r and \Z in addition
to documented 2-byte sequences: \0 and \N. This feature should be
documented (here backspace character is a default ESCAPED BY character,
in the real-life example it may be any ESCAPED BY character).

NOTE 2, changed behaviour:
Now the `SELECT INTO OUTFILE' statement with the `FIELDS ENCLOSED BY'
clause followed by one of: 'n', 't', 'r', 'b', '0', 'Z' or 'N' characters
encodes this special character itself by doubling it ('r' --> 'rr'),
not by prepending it with an escape character.

mysql-test/r/loaddata.result

-drop table if exists t1;
+drop table if exists t1,t2;
 create table t1 (a date, b date, c date not null, d date);
 load data infile '../../std_data/loaddata1.dat' into table t1 fields terminated by ',';
 Warnings:
@@ -85,3 +85,66 @@ field1	field2
 a"b	cd"ef
 a"b	c"d"e
 drop table t1;
+CREATE TABLE t1 (
+id INT AUTO_INCREMENT PRIMARY KEY,
+c1 VARCHAR(255)
+);
+CREATE TABLE t2 (
+id INT,
+c2 VARCHAR(255)
+);
+INSERT INTO t1 (c1) VALUES
+('r'),   ('rr'),   ('rrr'),   ('rrrr'),
+('.r'),  ('.rr'),  ('.rrr'),  ('.rrrr'),
+('r.'),  ('rr.'),  ('rrr.'),  ('rrrr.'),
+('.r.'), ('.rr.'), ('.rrr.'), ('.rrrr.'),
+('\r'),  ('\\rr'), ('\\\rr'), ('\\\\rr');
+SELECT * FROM t1;
+id	c1
+1	r
+2	rr
+3	rrr
+4	rrrr
+5	.r
+6	.rr
+7	.rrr
+8	.rrrr
+9	r.
+10	rr.
+11	rrr.
+12	rrrr.
+13	.r.
+14	.rr.
+15	.rrr.
+16	.rrrr.
+17	
+18	\rr
+19	\
r
+20	\\rr
+SELECT * INTO OUTFILE 'MYSQL_TEST_DIR/var/tmp/t1' FIELDS ENCLOSED BY 'r' FROM t1;
+r1r	rrrr
+r2r	rrrrrr
+r3r	rrrrrrrr
+r4r	rrrrrrrrrr
+r5r	r.rrr
+r6r	r.rrrrr
+r7r	r.rrrrrrr
+r8r	r.rrrrrrrrr
+r9r	rrr.r
+r10r	rrrrr.r
+r11r	rrrrrrr.r
+r12r	rrrrrrrrr.r
+r13r	r.rr.r
+r14r	r.rrrr.r
+r15r	r.rrrrrr.r
+r16r	r.rrrrrrrr.r
+r17r	r
r
+r18r	r\\rrrrr
+r19r	r\\
rrr
+r20r	r\\\\rrrrr
+LOAD DATA INFILE 'MYSQL_TEST_DIR/var/tmp/t1' INTO TABLE t2 FIELDS ENCLOSED BY 'r';
+SELECT t1.id, c1, c2 FROM t1 LEFT  JOIN t2 ON t1.id=t2.id WHERE c1 != c2;
+id	c1	c2
+SELECT t1.id, c1, c2 FROM t1 RIGHT JOIN t2 ON t1.id=t2.id WHERE c1 != c2;
+id	c1	c2
+DROP TABLE t1,t2;

mysql-test/t/loaddata.test

@@ -3,7 +3,7 @@
 #
 
 --disable_warnings
-drop table if exists t1;
+drop table if exists t1,t2;
 --enable_warnings
 
 create table t1 (a date, b date, c date not null, d date);
@@ -67,4 +67,40 @@ load data infile '../../std_data/loaddata5.dat' into table t1 fields terminated
 select * from t1;
 drop table t1;
 
+#
+# Bug #29294 SELECT INTO OUTFILE/LOAD DATA INFILE with special
+# characters in the FIELDS ENCLOSED BY clause
+#
+
+CREATE TABLE t1 (
+  id INT AUTO_INCREMENT PRIMARY KEY,
+  c1 VARCHAR(255)
+);
+
+CREATE TABLE t2 (
+  id INT,
+  c2 VARCHAR(255)
+);
+
+INSERT INTO t1 (c1) VALUES
+  ('r'),   ('rr'),   ('rrr'),   ('rrrr'),
+  ('.r'),  ('.rr'),  ('.rrr'),  ('.rrrr'),
+  ('r.'),  ('rr.'),  ('rrr.'),  ('rrrr.'),
+  ('.r.'), ('.rr.'), ('.rrr.'), ('.rrrr.'),
+  ('\r'),  ('\\rr'), ('\\\rr'), ('\\\\rr');
+SELECT * FROM t1;
+
+--exec rm -f $MYSQL_TEST_DIR/var/tmp/t1
+--replace_result $MYSQL_TEST_DIR MYSQL_TEST_DIR
+eval SELECT * INTO OUTFILE '$MYSQL_TEST_DIR/var/tmp/t1' FIELDS ENCLOSED BY 'r' FROM t1;
+--exec cat $MYSQL_TEST_DIR/var/tmp/t1
+
+--replace_result $MYSQL_TEST_DIR MYSQL_TEST_DIR
+eval LOAD DATA INFILE '$MYSQL_TEST_DIR/var/tmp/t1' INTO TABLE t2 FIELDS ENCLOSED BY 'r';
+SELECT t1.id, c1, c2 FROM t1 LEFT  JOIN t2 ON t1.id=t2.id WHERE c1 != c2;
+SELECT t1.id, c1, c2 FROM t1 RIGHT JOIN t2 ON t1.id=t2.id WHERE c1 != c2;
+
+--exec rm $MYSQL_TEST_DIR/var/tmp/t1
+DROP TABLE t1,t2;
+
 # End of 4.1 tests

sql/sql_class.cc

@@ -1020,6 +1020,7 @@ select_export::prepare(List<Item> &list, SELECT_LEX_UNIT *u)
   field_sep_char= (exchange->enclosed->length() ? (*exchange->enclosed)[0] :
 		   field_term_length ? (*exchange->field_term)[0] : INT_MAX);
   escape_char=	(exchange->escaped->length() ? (*exchange->escaped)[0] : -1);
+  is_ambiguous_field_sep= strchr(ESCAPE_CHARS, field_sep_char);
   line_sep_char= (exchange->line_term->length() ?
 		  (*exchange->line_term)[0] : INT_MAX);
   if (!field_term_length)
@@ -1113,7 +1114,9 @@ bool select_export::send_data(List<Item> &items)
 	      (int) *pos == line_sep_char || !*pos)
 	  {
 	    char tmp_buff[2];
-	    tmp_buff[0]= escape_char;
+            tmp_buff[0]= ((int) *pos == field_sep_char &&
+                          is_ambiguous_field_sep) ?
+                          field_sep_char : escape_char;
 	    tmp_buff[1]= *pos ? *pos : '0';
 	    if (my_b_write(&cache,(byte*) start,(uint) (pos-start)) ||
 		my_b_write(&cache,(byte*) tmp_buff,2))

sql/sql_class.h

@@ -1224,9 +1224,18 @@ public:
 };
 
 
+#define ESCAPE_CHARS "ntrb0ZN" // keep synchronous with READ_INFO::unescape
+
+
 class select_export :public select_to_file {
   uint field_term_length;
   int field_sep_char,escape_char,line_sep_char;
+  /*
+    The is_ambiguous_field_sep field is true if a value of the field_sep_char
+    field is one of the 'n', 't', 'r' etc characters
+    (see the READ_INFO::unescape method and the ESCAPE_CHARS constant value).
+  */
+  bool is_ambiguous_field_sep;
   bool fixed_row_size;
 public:
   select_export(sql_exchange *ex) :select_to_file(ex) {}

sql/sql_load.cc

@@ -611,6 +611,7 @@ read_sep_field(THD *thd,COPY_INFO &info,TABLE *table,
 char
 READ_INFO::unescape(char chr)
 {
+  /* keep this switch synchornous with the ESCAPE_CHARS macro */
   switch(chr) {
   case 'n': return '\n';
   case 't': return '\t';