…enabled Faster queries through speedier joins, faster subqueries, and elimination of useless tables in joins Thread pooling and a segmented key …are three great versions of MySQL that suit different needs and personalities, with different characteristics, and feature and performance improvements are …
Post: Joining many tables in MySQL - optimizer_search_depth
April 20, 2012 By 6 Comments
…though in the read less than 1000 rows and doing it completely in memory. The plan … points to problem with optimizer performance. Note though if you have subqueries these might need to be …want to risk likehood of execution plans changing for some over queries joining less number of tables. I …
Post: Shard-Query turbo charges Infobright community edition (ICE)
May 6, 2011 By 22 Comments
… “scaling out” and it allows Shard-Query to vastly improve the performance of queries which have to examine a large amount of data. Shard… added parallelism, and when one of the the following are in used in the query: BETWEEN or IN clauses, subqueries in the FROM… from ontime_fact join dim_date using (date_id) GROUP BY Year) t2 ON (t.Year=t2.Year); The performance of the following…
Post: MySQL VIEW as performance troublemaker
August 12, 2007 By 53 Comments
… on top of one another so it is easy to write the queries, some of them it turn used subqueries subselects and derived tables… as with subqueries and derived tables MySQL 5.0 will fail and perform very inefficiently in many counts. MySQL has two ways of handling the… and “full join” used to to join between them. In this particular case it is not that bad because “join cache” is used to perform…
Post: MySQL Limitations Part 3: Subqueries
October 25, 2010 By 20 Comments
… about subqueries, which in some cases execute outside-in instead of inside-out as users expect. It’s easy to pick on subqueries… happens instead is usually a full scan or index scan of table a, followed by N queries to table b. This… poor subquery performance, or have had it in the past and have fixed it. And many MySQL users have learned to simply write JOINs instead…
Post: Distributed Set Processing with Shard-Query
May 14, 2011 By 27 Comments
…of sets? From a distributed processing standpoint, rows are the worst case for performance. Optimal mathematical performance… materialized view over a union of all the already joined and aggregated data from all … This allows BETWEEN, IN, subqueries in the FROM clause, and UNION operations to operate …
Comment: Database problems in MySQL/PHP Applications
August 11, 2006 By 12 Comments
…subqueries Where Subselects with IN() become > corellated even if they are not, and so using IN() list of…of JOIN to use so that the right number of rows are scanned and returned. SELECT * FROM articles INNER JOIN…
Post: Database problems in MySQL/PHP Applications
August 11, 2006 By 12 Comments
… your data however it does not always bring good performance. Joins are expensive and you can often do much better with denormalized data… 100 of queries in this case. This most applies to subqueries Where Subselects with IN() become corellated even if they are not, and so using IN() list of values derived…
Post: Missing Data - rows used to generate result set
July 20, 2008 By 15 Comments
…of rows returned by the query but number of rows accessed by the query will most likely be defining query performance. Of… to reach for small fraction of queries. If you’re joining multiple tables or if you …USA’ As of MySQL 5.0 MySQL will materialize the subquery in the from clause fully and so “use…
Comment: How expensive is a WHERE clause in MySQL?
August 4, 2010 By 16 Comments
… the JOIN size. Because the other side of the JOIN already limited the records as needed, the WHERE clause on the first subquery was unneeded. I assumed that having a smaller resultset would increase performance because less memory was copied and used; however…
