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With the standard data warehousing queries we have a fact table and dimension tables and we join them. For example, the fact table (Table size: 5M rows, ~2G in size) from my previous Loose index scan vs. covered indexes in MySQL post: CREATE TABLE `ontime_2010` ( `YearD` int(11) DEFAULT NULL, `MonthD` tinyint(4) DEFAULT NULL, `DayofMonth` […] Lets say we have a table storing mail messages and we need to show user’s mailbox: messages sent “from” and “to” the specified user. Here is our table: CREATE TABLE `internalmail` ( `mail_id` int(10) NOT NULL AUTO_INCREMENT, `senderaddress_id` int(10) NOT NULL, `recipientaddress_id` int(10) NOT NULL, `mail_timestamp` timestamp NULL DEFAULT NULL, … message body, etc … […] Loose index scan in MySQL can really help optimizing “group by” queries in some cases (for example, if you have only min() and/or max() as your aggregate functions). For example, if you have this query (to find maximum delay for all US flights with departure on Sundays in 2010): select max(DepDelayMinutes), carrier, dayofweek from ontime_2010 […] First of all: mysqldump is not converting tables. It is something else. Here is the story: One of my clients had a case when they were migrating to a new mysql server: they used mysqldump to export data from the old server (all InnoDB) and imported it to the new server. When finished, all the […] |
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