… about redundant indexes and mentioned sometimes it is good to leave two indexes, even one is first part of another. I’m speaking about BTREE indexes…, that is almost +100% comparing with non-convering index. But if run the test for Q1 we have: 25.40 q/s, that in… – 470sec (Here I limited available memory to fit only one index, that shows how can degrade performance if we balance on memory…
Comment: Duplicate indexes and redundant indexes
September 22, 2006 By 38 Comments
… while, I found out that at least in MySQL, the prefix redundancy problem just cannot occur for RTREE Spatial index, because they cannot… and non-covering index could give worse performance over a shorter unique index that is the prefix of the longer one – would that be because time would be wasted reading the index, because the…
Post: How to recover deleted rows from an InnoDB Tablespace
February 20, 2012 By 3 Comments
… is our tablespace located (-f) The row format can be -4 (REDUNDANT) or -5 (COMPACT). From 5.0.3 the default format is… are two indexes with the IDs 0-26 and 0-27. InnoDB has Clustered Primary Key, that is, the data is organized along with… it the tool needs to know the table schema structure, that is, column types, names and attributes. This information needs to be…
Post: Getting MySQL to use full key length
January 31, 2007 By 5 Comments
… index can be used or using shorter index while there is longer index available. The last item is yet another good reason for removing redundant indexes Here is… select something like (A,D) using only first keypart of that index. To fix this problem I guess another statistics alignment should…
Post: Shard-Query EC2 images available
May 11, 2011 By 2 Comments
… is possible to distribute splitting and/or loading among multiple nodes as well. Note that in the demonstration each node will contain redundant… not have any indexes (not even primary keys). Here is the complete InnoDB schema from one shard. The schema is duplicated 20 times…_workers 80 I normally start (2 * TOTAL_CLUSTER_CORES) workers. That is, if you have 20 machines, each with 2 cores, run…
Comment: Redundant index is not always bad
August 29, 2007 By 7 Comments
… mean redundant indexes. Say one with ‘cola’ and another with ‘(cola, colb)’. The merge intersect will not work in a query that doesn… problem that if you have two redundant indexes and you are filtering on ‘cola’ and ‘colb’ it will often choose to use both indexes with merge intersect which is completly a waste of time as only the muti-key index should be used…
Comment: Duplicate indexes and redundant indexes
September 21, 2006 By 38 Comments
… index UI and a nordinay index I, again of the same type. Then, clearly, UI would not be redundant even if its columnlist is a prefix of the columnlist of I. UI might be redundant in the sense that it… index a UNIQUE one too? By definition, the values in the longer index are unique too, and telling the database that the longer index is…
Post: RAID and Scale Out Discussions
June 12, 2007 By 3 Comments
… drives for search index because it is far faster than using software RAID. But this is only because Sphinx … (software) is what we use even for low end boxes. This has zero cost and offer redundancy in … much anyway. Not all the needs are satisfied that well by vendors. Dell for example for some …
Post: How Percona does a MySQL Performance Audit
November 24, 2008 By 17 Comments
… the mysql.* tables, running mk-duplicate-key-checker to find redundant indexes, and so on. As with settings and status, these set… all that much time here, although there is occasionally something really bad that can be fixed and bring big gains. Schema, query, and index optimization Analyzing and optimizing a server’s table and index structures, and the queries that run against them, is by far…
Comment: System size and Performance Optimization
March 1, 2007 By 2 Comments
… I use an “index on soundex(columns) and index on soundex(reverse(columsn)) Today I have to hold create redundant columns in MySQL to hold soundex of columns to able to create the index. I think for… the indexes without creating the column. Oher RDMS like Postgres support this. What is your opinion on this? Would you think that support…
