… use of subqueries/multiple joins vs. multiple queries (e.g. temp tables)? For performance, it’s hard to… poor performance, but it returns a better random choice. Another workaround may be to add a column to … was that it created a temporary table to count the movies per production year for each kind_…
Post: COUNT(*) vs COUNT(col)
April 10, 2007 By 45 Comments
… it is able to instantly answer COUNT(*) and COUNT(val2) queries, but not COUNT(val). Why ? Because val column is not defined as NOT… different for the second query. So COUNT(*) and COUNT(col) queries not only could have substantial performance performance differences but also ask different question…
Post: InnoDB vs MyISAM vs Falcon benchmarks - part 1
January 8, 2007 By 117 Comments
… in Part 2). There MyISAM shows bad scalability with increasing count of thread. I think the reason is pread system call… LIMIT properly and that is why we see bad performance. We hope the performance of LIMIT queries will be fixed before release… count(id) FROM $tableName WHERE id between %d and %d MyISAM scales good here, because of access only to key column and…
Post: PBXT benchmarks
April 8, 2007 By 14 Comments
… to ones in benchmark InnoDB vs MyISAM vs Falcon (http://www.mysqlperformanceblog… different the values of accessed column is stored in key. Interesting…READ_PK_RANGE_INDEX Query: SELECT count(id) FROM $tableName WHERE id between…I hope PBXT team will improve performance to make the difference a …
Comment: Air traffic queries in InfiniDB: early alpha
November 3, 2009 By 19 Comments
…first pass at your observation: LOAD DATA INFILE vs. InfiniDB bulk load (cpimport): We provided support …columns are NULL in the input datasets. They use 0 bytes in the input file (1 if you count…and returns all of them to MySQL to perform the aggregation. q4: For future reference, ‘service infinidb …
Post: Index Condition Pushdown in MySQL 5.6 and MariaDB 5.5 and its performance impact
March 12, 2012 By 12 Comments
I have been working with Peter in preparation for the talk comparing the optimizer enhancements in MySQL 5.6 and MariaDB 5.5. We are taking a look at and benchmarking optimizer enhancements one by one. So in the same way this blog post is aimed at a new optimizer enhancement Index Condition …
Post: Using index for ORDER BY vs restricting number of rows.
February 16, 2007 By 8 Comments
… also bunch of fields which sorting can be performed on such as seller, price, date added etc….MySQL would need to better take into account column selectivity together with LIMIT range. If there are…The other problem you may have however is calculating count of matching rows which may be even trickier…
Post: Why MySQL could be slow with large tables ?
June 9, 2006 By 141 Comments
… 30 millions of rows. “val” column in this table has 10000 distinct… table scan vs range scan by index: mysql> select count(pad) from large; +————+ | count(pad) | +————+ | 31457280 …previously normalized to several tables or perform complex queries finding relationships between objects…
