Percona's MySQL & InnoDB performance and scalability blog
…multiple joins vs. multiple queries (e.g. temp tables)? For performance, it’s hard to make a general rule, because there are different…multiple columns in a compound index, then the order would matter, and it would have to match the order of columns…
…difference. Here is little illustration I’ve created the table with over 30 millions of rows. “val” column in this table…selects about 1% of the table. The times for full table scan vs range scan by index: mysql> select count(pad) from…
…multiple columns: Q1 SELECT sum(length(val)) FROM T WHERE i=2 AND j=1 Q2 SELECT sum(length(val)) FROM…tables to show what difference large BETWEEN can make. Conclusion: For benchmarked queries we can see Multiple Column…
…column. It is used to prevent wide innodb primary keys on the MV. mysql> select…mysql> select sum(total_lines) cnt from dashboard_top_customers\G *************************** 1. row *************************** cnt: 155187034 1 row in set (0.03 sec) Notice the difference…
…column and I would expect “Impossible Where clause” here Lets look at query execution: | Handler_read_next | 1305742982 | mysql> select count(*) from…multiple table and the column type was inconsistent between them… so inserts into one table…
… often have tables with lots of single-column indexes on columns which commonly …columns that had single-column indexes on them, MySQL could sometimes make use of the multiple indexes. For instance, “SELECT foo FROM… not look too bad. MySQL is using three different indexes to search approximately …
…MySQL always uses Nested Loop Join to join two or more tables. What this means is that, select rows from first table…multiple times. Consider if you have a small buffer pool and a very large number of rows from…
…MySQL does not know it as it looks at stats from different…multiple column indexes. This is in case you’re using OR between the columns. In this case the combined index is useless and MySQL…
…mysql: SELECT id, title, MATCH(title, body) AGAINST (‘arizona business records’ IN NATURAL LANGUAGE MODE) AS score FROM…
…TABLE, and that we might have to run OPTIMIZE TABLE multiple times if we’ve had a lot of changes to the table…mysql> set global innodb_ft_aux_table=’test/dir_test_innodb’; mysql> set global innodb_optimize_fulltext_only=1; mysql> select * from…
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