Bug#10418: LOAD_FILE does not behave like in manual if file does not exist

load_file() string-function should return NULL rather than throw an error if
the file doesn't exist, as per the manual.


mysql-test/t/outfile.test:
  expect NULL rather than error if file given to load_file() doesn't exist
mysql-test/t/func_str.test:
  show that load_file() will return NULL rather than throw an error
  if file doesn't exist
mysql-test/r/outfile.result:
  expect NULL rather than error if file given to load_file() doesn't exist
mysql-test/r/func_str.result:
  expect NULL rather than error if file given to load_file() doesn't exist
sql/item_strfunc.cc:
  load_file() should return NULL as per the docs if file not found,
  rather than throw an error

mysql-test/r/func_str.result

@@ -1000,3 +1000,10 @@ t
 1000000
 1      
 drop table t1;
+select load_file("lkjlkj");
+load_file("lkjlkj")
+NULL
+select ifnull(load_file("lkjlkj"),"it's null");
+ifnull(load_file("lkjlkj"),"it's null")
+it's null
+End of 4.1 tests

mysql-test/t/func_str.test

@@ -662,4 +662,11 @@ select rpad(i, 7, ' ') as t from t1;
 --disable_metadata
 drop table t1;
 
-# End of 4.1 tests
+#
+# Bug #10418: LOAD_FILE does not behave like in manual if file does not exist
+#
+
+select load_file("lkjlkj");
+select ifnull(load_file("lkjlkj"),"it's null");
+
+--echo End of 4.1 tests

mysql-test/t/outfile.test

@@ -38,7 +38,6 @@ select load_file(concat(@tmpdir,"/outfile-test.3"));
 #--error 1086
 #eval select * into dumpfile "$MYSQL_TEST_DIR/var/tmp/outfile-test.3" from t1;
 #enable_query_log;
---error 13,2
 select load_file(concat(@tmpdir,"/outfile-test.not-exist"));
 --exec rm $MYSQL_TEST_DIR/var/tmp/outfile-test.1
 --exec rm $MYSQL_TEST_DIR/var/tmp/outfile-test.2