I still don't understand
Yes sorry, I just realized I wrote something stupid: the index is not unique. Roberto, maybe you meant that teste is unique because you know it is unique? But then, declare it as unique. But don't expect the query plans to change. Federico -------------------------------------------- Mar 23/6/15, Reindl Harald <h.reindl@thelounge.net> ha scritto: Oggetto: Re: [Maria-discuss] doubt about index A: maria-discuss@lists.launchpad.net Data: Martedì 23 giugno 2015, 01:31 Am 23.06.2015 um 01:20 schrieb Federico Razzoli: the matter.
"teste" is a unique index, because part of it is unique no it is not *because* only a part of it is unique
But it is not declared as unique, and MariaDB is not suppose to read our minds.
hence it is not
The query written by Reindl looks realistic, but it would use the primary key, and I would be disappointed if it used "teste".
i won't and that is *clearly* statet in the docs
Are we talking about real-world needs, or just speculation?
likely speculation
--------------------------------------------
Mar 23/6/15, Reindl Harald <h.reindl@thelounge.net> ha scritto:
Oggetto: Re: [Maria-discuss] doubt about index A: "Maria Discuss" <maria-discuss@lists.launchpad.net> Data: Martedì 23 giugno 2015, 01:13
Am 23.06.2015 um 00:53 schrieb Roberto Spadim: > 2015-06-22 19:47 GMT-03:00 Reindl Harald <h.reindl@thelounge.net > <mailto:h.reindl@thelounge.net>>: > > Am 23.06.2015 um 00:43 schrieb Roberto Spadim: > > hi guys, i`m with a doubt... > when i have a primary key i know that's a unique key > when i have a index with primary key + any other
column, does > > mariadb > > consider that > it's unique too? > > > > > > if it > is defined as unique key yes > > > > what is "index with > primary key + any other column"? > > > > > > > for example > > create table x( > > i int, > > b int, > > c int, d int , e int, ... > > primary key(i), > > key > teste(b,i) > > ) > > > > the test index is primary key (i column) + > any other column (b,c,d,e,...) > > these are two indexes > > the second one is completly nosense as long > your qquery is not in the > form of > "where b=x and i=y" and even "where i=y and > b=x" won't be able > to use it > > >> you have two keys > in that case and the select uses one of them > > > > yeap but some search > algorithms use unique key/non unique key > > information to improve search right? > > which part of the > documentation says that? > > > does it consider that any index that > contains a unique index columns + > > > anyother column as "unique" > > why should it? > it must not > just because they are not > > > i`m thinking more > about SELECT optimization > > > > > > how > does it matter if a key is unique or not for select > optimization? > > > > > select "where i=1" should return 0/1 rows > (it's unique), > > "where > b=1" should return 0+ rows, but "where b=1 and > i=1" should return > > 0/1 > rows > > it don't > matter at all, these are two seperate indexes
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