It seems you are right. It has nothing to do with the SQLAlchemy. I checked the Galaxy log and didn't find any other error log. After upgrading the database to MySQL when I uploaded the first input file, job dispatched to local runner and everything was fine. But when I tried to upload another file Galaxy didn't even dispatched the Job. I am pasting below the snapshot of the Galaxy log for your reference.
galaxy.datatypes.metadata DEBUG 2013-07-23 09:36:15,579 Cleaning up external metadata files
10.180.4.152 - - [23/Jul/2013:09:36:15 +0600] "GET /api/histories/f2db41e1fa331b3e HTTP/1.1" 200 - "
http://10.180.8.54:6080/history" "Mozilla/5.0 (X11; Linux i686) AppleWebKit/537.4 (KHTML, like Gecko) Chrome/22.0.1229.94 Safari/537.4"
10.180.4.152 - - [23/Jul/2013:09:36:15 +0600] "GET /api/users/current HTTP/1.1" 200 - "
http://10.180.8.54:6080/" "Mozilla/5.0 (X11; Linux i686) AppleWebKit/537.4 (KHTML, like Gecko) Chrome/22.0.1229.94 Safari/537.4"
10.180.4.152 - - [23/Jul/2013:09:36:15 +0600] "GET /api/histories/f2db41e1fa331b3e/contents?ids=ebfb8f50c6abde6d HTTP/1.1" 200 - "
http://10.180.8.54:6080/history" "Mozilla/5.0 (X11; Linux i686) AppleWebKit/537.4 (KHTML, like Gecko) Chrome/22.0.1229.94 Safari/537.4"
10.180.4.152 - - [23/Jul/2013:09:36:33 +0600] "GET /tool_runner?tool_id=upload1 HTTP/1.1" 200 - "
http://10.180.8.54:6080/" "Mozilla/5.0 (X11; Linux i686) AppleWebKit/537.4 (KHTML, like Gecko) Chrome/22.0.1229.94 Safari/537.4"
10.180.4.152 - - [23/Jul/2013:09:36:38 +0600] "POST /tool_runner/upload_async_create HTTP/1.1" 200 - "
http://10.180.8.54:6080/" "Mozilla/5.0 (X11; Linux i686) AppleWebKit/537.4 (KHTML, like Gecko) Chrome/22.0.1229.94 Safari/537.4"
10.180.4.152 - - [23/Jul/2013:09:36:38 +0600] "GET /tool_runner/upload_async_message HTTP/1.1" 200 - "
http://10.180.8.54:6080/" "Mozilla/5.0 (X11; Linux i686) AppleWebKit/537.4 (KHTML, like Gecko) Chrome/22.0.1229.94 Safari/537.4"
10.180.4.152 - - [23/Jul/2013:09:37:01 +0600] "GET /tool_runner?tool_id=upload1 HTTP/1.1" 200 - "
http://10.180.8.54:6080/" "Mozilla/5.0 (X11; Linux i686) AppleWebKit/537.4 (KHTML, like Gecko) Chrome/22.0.1229.94 Safari/537.4"
10.180.4.152 - - [23/Jul/2013:09:37:08 +0600] "POST /tool_runner/upload_async_create HTTP/1.1" 200 - "
http://10.180.8.54:6080/" "Mozilla/5.0 (X11; Linux i686) AppleWebKit/537.4 (KHTML, like Gecko) Chrome/22.0.1229.94 Safari/537.4"
10.180.4.152 - - [23/Jul/2013:09:37:08 +0600] "GET /tool_runner/upload_async_message HTTP/1.1" 200 - "
http://10.180.8.54:6080/" "Mozilla/5.0 (X11; Linux i686) AppleWebKit/537.4 (KHTML, like Gecko) Chrome/22.0.1229.94 Safari/537.4"
10.180.4.152 - - [23/Jul/2013:09:37:53 +0600] "GET /history HTTP/1.1" 200 - "
http://10.180.8.54:6080/" "Mozilla/5.0 (X11; Linux i686) AppleWebKit/537.4 (KHTML, like Gecko) Chrome/22.0.1229.94 Safari/537.4"
10.180.4.152 - - [23/Jul/2013:09:37:53 +0600] "GET /api/histories/f2db41e1fa331b3e HTTP/1.1" 200 - "
http://10.180.8.54:6080/history" "Mozilla/5.0 (X11; Linux i686) AppleWebKit/537.4 (KHTML, like Gecko) Chrome/22.0.1229.94 Safari/537.4"
10.180.4.152 - - [23/Jul/2013:09:37:53 +0600] "GET /history/get_display_application_links HTTP/1.1" 200 - "
http://10.180.8.54:6080/history" "Mozilla/5.0 (X11; Linux i686) AppleWebKit/537.4 (KHTML, like Gecko) Chrome/22.0.1229.94 Safari/537.4"
10.180.4.152 - - [23/Jul/2013:09:37:57 +0600] "GET / HTTP/1.1" 200 - "-" "Mozilla/5.0 (X11; Linux i686) AppleWebKit/537.4 (KHTML, like Gecko) Chrome/22.0.1229.94 Safari/537.4"
10.180.4.152 - - [23/Jul/2013:09:37:57 +0600] "GET /root/welcome HTTP/1.1" 302 - "
http://10.180.8.54:6080/" "Mozilla/5.0 (X11; Linux i686) AppleWebKit/537.4 (KHTML, like Gecko) Chrome/22.0.1229.94 Safari/537.4"
10.180.4.152 - - [23/Jul/2013:09:37:57 +0600] "GET /history HTTP/1.1" 200 - "
http://10.180.8.54:6080/" "Mozilla/5.0 (X11; Linux i686) AppleWebKit/537.4 (KHTML, like Gecko) Chrome/22.0.1229.94 Safari/537.4"
10.180.4.152 - - [23/Jul/2013:09:37:57 +0600] "GET /history/get_display_application_links HTTP/1.1" 200 - "
http://10.180.8.54:6080/history" "Mozilla/5.0 (X11; Linux i686) AppleWebKit/537.4 (KHTML, like Gecko) Chrome/22.0.1229.94 Safari/537.4"
10.180.4.152 - - [23/Jul/2013:09:37:57 +0600] "GET /api/histories/f2db41e1fa331b3e HTTP/1.1" 200 - "
http://10.180.8.54:6080/history" "Mozilla/5.0 (X11; Linux i686) AppleWebKit/537.4 (KHTML, like Gecko) Chrome/22.0.1229.94 Safari/537.4"
10.180.4.152 - - [23/Jul/2013:09:38:02 +0600] "GET /api/histories/f2db41e1fa331b3e HTTP/1.1" 200 - "
http://10.180.8.54:6080/history" "Mozilla/5.0 (X11; Linux i686) AppleWebKit/537.4 (KHTML, like Gecko) Chrome/22.0.1229.94 Safari/537.4"
10.180.4.152 - - [23/Jul/2013:09:38:06 +0600] "GET /api/histories/f2db41e1fa331b3e HTTP/1.1" 200 - "
http://10.180.8.54:6080/history" "Mozilla/5.0 (X11; Linux i686) AppleWebKit/537.4 (KHTML, like Gecko) Chrome/22.0.1229.94 Safari/537.4"
10.180.4.152 - - [23/Jul/2013:09:38:10 +0600] "GET /api/histories/f2db41e1fa331b3e HTTP/1.1" 200 - "
http://10.180.8.54:6080/history" "Mozilla/5.0 (X11; Linux i686) AppleWebKit/537.4 (KHTML, like Gecko) Chrome/22.0.1229.94 Safari/537.4"
10.180.4.152 - - [23/Jul/2013:09:38:14 +0600] "GET /api/histories/f2db41e1fa331b3e HTTP/1.1" 200 - "
http://10.180.8.54:6080/history" "Mozilla/5.0 (X11; Linux i686) AppleWebKit/537.4 (KHTML, like Gecko) Chrome/22.0.1229.94 Safari/537.4"
10.180.4.152 - - [23/Jul/2013:09:38:18 +0600] "GET /api/histories/f2db41e1fa331b3e HTTP/1.1" 200 - "
http://10.180.8.54:6080/history" "Mozilla/5.0 (X11; Linux i686) AppleWebKit/537.4 (KHTML, like Gecko) Chrome/22.0.1229.94 Safari/537.4"
10.180.4.152 - - [23/Jul/2013:09:38:22 +0600] "GET /api/histories/f2db41e1fa331b3e HTTP/1.1" 200 - "
http://10.180.8.54:6080/history" "Mozilla/5.0 (X11; Linux i686) AppleWebKit/537.4 (KHTML, like Gecko) Chrome/22.0.1229.94 Safari/537.4"
10.180.4.152 - - [23/Jul/2013:09:38:24 +0600] "POST /datasets/33b43b4e7093c91f/delete_async HTTP/1.1" 200 - "
http://10.180.8.54:6080/history" "Mozilla/5.0 (X11; Linux i686) AppleWebKit/537.4 (KHTML, like Gecko) Chrome/22.0.1229.94 Safari/537.4"
Thanks