[datafeed] make cnxset handling of datafeed source more robust
currently we may run in some cases where the session has no more cnxset
depending on errors and parser's handling of the cnxset.
Also, free the cnxset and reacquire it later, letting a chance to other
threads to run.
/* -*- sql -*- mysql specific registered procedures, *//* XXX limit_size version dealing with format as postgres version does. XXX mysql doesn't support overloading, each function should have a different name NOTE: fulltext renamed since it cause a mysql name conflict */CREATEFUNCTIONtext_limit_size(vfulltextTEXT,maxsizeINT)RETURNSTEXTNOSQLBEGINIFLENGTH(vfulltext)<maxsizeTHENRETURNvfulltext;ELSERETURNSUBSTRING(vfulltextfrom1formaxsize)||'...';ENDIF;END;;