I think I can explain the performance you are seeing. But first I’d like … not properly indexed. Here’s a theory that seems to explain the performance you are seeing. The periodic performance variation corresponds…
Comment: Multi Column indexes vs Index Merge
May 10, 2012 By 30 Comments
… had a question regarding index merge (intersect). Below are two explains that I executed for the same SQL query with a… a single index. I would greatly appreciate your answer. First explain —————– explain SELECT LinksTbl2.id, LinksTbl2.title, LinksTbl2.url, PersonTbl2.firstname, PersonTbl2…
Comment: How to load large files safely into InnoDB with LOAD DATA INFILE
May 10, 2012 By 28 Comments
… is the right strategy to go with. But can you explain why I’m witnessing the LOAD DATA INFILE command being…
Post: Testing Fusion-io ioDrive
May 3, 2012 By 1 Comment
… 0 to 1800 sec): I am not sure how to explain it, that with 4 and 8 threads the pattern is…
Comment: Testing Intel SSD 520
May 3, 2012 By 7 Comments
…/solid-state-drives/ssd-520-tech-brief.html That may explain why do we see such variance in throughput.
Comment: UNION vs UNION ALL Performance
May 2, 2012 By 13 Comments
… option 2 will be better to achieve this but the explain plan shows less cost for option 1. Can anybody tell…
Post: Join Optimizations in MySQL 5.6 and MariaDB 5.5
April 4, 2012 By 2 Comments
… also look at, in this post. Now let me briefly explain these optimizations. Batched Key Access Traditionally, MySQL always uses Nested…. The storage engine then uses the MRR interface (which I explained in my previous post) to lookup the rows in table2… algorithm only works with equi-joins. Now let me briefly explain how hash join algorithm works. Suppose you have two tables…
Comment: What does Using filesort mean in MySQL?
March 15, 2012 By 27 Comments
… uses index (type: index, key: a, key_len: 103, Extra: ”): EXPLAIN SELECT * FROM table1 ORDER BY a LIMIT 1698, 1 This… filesort (Extra: Using filesort): EXPLAIN SELECT * FROM table1 ORDER BY a LIMIT 1699, 1 Can someone EXPLAIN if there is a rule… but it does not. I just see this note: With EXPLAIN SELECT … ORDER BY, you can check whether MySQL can use…
Post: Joining many tables in MySQL - optimizer_search_depth
April 20, 2012 By 5 Comments
… optimizer picked was very good one, yet you could notice EXPLAIN itself was taking same 5 seconds, which points to problem… you have subqueries these might need to be executed during EXPLAIN phase yet making it unusable to check the optimizer performance…
Comment: InnoDB's gap locks
April 13, 2012 By 14 Comments
Hi all, I’m going to try to explain the following phrase with an example: “InnoDB provides REPEATABLE READ …
