Hi Roberto 1) Can't you use a relational table? (obvious suggestion, so probably the answer is no. but since MariaDB is relational, this is the main source of your troubles...) 2) If you need 1 row, why should an application send a query like that? It should send the simple SELECT first, and only if no row is found, it should try the non-optimizable SELECTs. If (for some reason I cannot know) this requires too many changes to the application, a simple stored procedure could do the same thing. 3) In case you are using MariaDB 10.0, did you check if this optimization is used? https://mariadb.com/kb/en/mariadb/documentation/optimization-and-tuning/quer... Tchau! Federico -------------------------------------------- Mar 12/8/14, Roberto Spadim <roberto@spadim.com.br> ha scritto: Oggetto: [Maria-discuss] optimization A: "Maria Discuss" <maria-discuss@lists.launchpad.net> Data: Martedì 12 agosto 2014, 22:19 guys, i have some queries like this: SELECT doc_hash_key FROM mov_documentos WHERE doc_hash_key LIKE "j;1;$;294007/3nfe-1%" UNION SELECT doc_hash_key FROM mov_documentos WHERE doc_hash_key LIKE "j;1;%;294007/3nfe-1%" UNION SELECT doc_hash_key FROM mov_documentos WHERE doc_hash_key LIKE "j;1;%;%294007/3nfe-1%" UNION SELECT doc_hash_key FROM mov_documentos WHERE doc_hash_key LIKE "%;%;$;%294007/3nfe-1%" UNION SELECT doc_hash_key FROM mov_documentos WHERE doc_hash_key LIKE "%;%;%;294007/3nfe-1%" UNION SELECT doc_hash_key FROM mov_documentos WHERE doc_hash_key LIKE "%;%;%;%294007/3nfe-1%" LIMIT 1 it's a search about a document number, but the problem is.... the first query at first line (with % at end of the query) return really fast, but executing others queries are very slow, the question is could we optimize this kind of query, since limit=1 row?the explain of this query: id select_typetable typepossible_keys keykey_len refrows Extra1 PRIMARYmov_documentos rangePRIMARY PRIMARY77 1 Using where; Using index2 UNIONmov_documentos rangePRIMARY PRIMARY77 625612 Using where; Using index3 UNIONmov_documentos rangePRIMARY PRIMARY77 625612 Using where; Using index4 UNIONmov_documentos index PRIMARY77 1798490 Using where; Using index5 UNIONmov_documentos index PRIMARY77 1798490 Using where; Using index6 UNIONmov_documentos index PRIMARY77 1798490 Using where; Using index UNION RESULT<union1,2,3,4,5,6> ALL -- Roberto Spadim -----Segue allegato----- _______________________________________________ Mailing list: https://launchpad.net/~maria-discuss Post to : maria-discuss@lists.launchpad.net Unsubscribe : https://launchpad.net/~maria-discuss More help : https://help.launchpad.net/ListHelp