… implemented true-VARCHAR support for MEMORY tables for MySQL 5.0. Although this patch did not add the BLOB and TEXT support, it refactored the… tables are still used for temporary tables where the MEMORY tables with dynamic row format could be used instead: for schemas containing large VARCHARs, BLOB, TEXT…
Post: Percona Server 5.5.15-21.0
August 31, 2011 By 9 Comments
… limitation, the Improved MEMORY Storage Engine is introduced in this release for supporting true VARCHAR, VARBINARY, TEXT and BLOB fields in MEMORY tables. This implementation is based on the Dynamic Row Format (DFR) introduced by the mysql-heap-dynamic…
Post: How much overhead is caused by on disk temporary tables
August 16, 2007 By 26 Comments
…put to temporary tables – BLOB/TEXT columns are not supported with MEMORY storage engine so must use on disk MyISAM temporary table. What i …memory MEMORY temporary tables can be 10-100 times faster than disk based MyISAM tables Hopefully MySQL will implement support of dynamic rows for MEMORY tables…
Post: TMP_TABLE_SIZE and MAX_HEAP_TABLE_SIZE
January 19, 2007 By 16 Comments
…should increase tmp_table_size to appropriate value and avoid using blob/text columns which force table creation on the disk because MEMORY storage engine…dev.mysql.com/doc/refman/5.0/en/memory-storage-engine.html MEMORY table contents are stored in memory, which is a property that MEMORY tables …
Post: Heikki Tuuri Innodb answers - Part I
October 26, 2007 By 17 Comments
…blobs/text fields (needs more info) According to the documentation, InnoDB put first 768 chars of each text/blob… the system’s memory the kernel can decide (incorrectly) to swap out MySQL. There are two …example, if ORDER and ORDERLINE tables are joined to form a single table), it might make sense…
Post: MySQL Prepared Statements
August 2, 2006 By 19 Comments
… was sent as text and result returned back as text. For example number …copying Avoid SQL Injection Save memory on handling blobs There are also drawbacks …you can’t use them for table name. In certain version it … close prepared statements – Many memory leaks reported in MySQL Server turned out to …
Comment: How much overhead is caused by on disk temporary tables
August 17, 2007 By 26 Comments
… fits in memory using in memory table is better in most cases. I mainly did this comparison keeping in mind cases when BLOB/TEXT can’t be used because I expect them to have similar overhead (though I can try converting this column to TEXT to see how long time changes) There is another reason – MySQL only allows you to set tmp_table_site per…
Comment: Slow DROP TABLE
June 17, 2009 By 20 Comments
… where tables are created in /tmp : – when you use “create temporary table” – when MySQL need a temporary table which use BLOB or TEXT column – when MySQL need a temporary table which is bigger than tmp_table_size/max_heap_table… case, we can’t use /dev/shm to store temporary tables : it may use too much memory.
Comment: How much overhead is caused by on disk temporary tables
April 21, 2008 By 26 Comments
… tmpfs vs heap table to see how it works. In general of course it would be great if MySQL would have the… support BLOB/TEXT in memory tables and there is Maria comming which will cache the data in pagecache avoiding disk IO for temp tables if…
Post: How number of columns affects performance ?
September 28, 2009 By 10 Comments
… for dynamic rows tables certain conversion has to take place when internal data structures are populated (everything but TEXTs/BLOBs is fixed length… with such wide tables is to use covering indexes. I added one to t99v1 table and repeated the query: mysql [localhost] {msandbox} (test… Innodb when it comes to in memory full table scan. P.S Tests were done on MySQL 5.4.2 on Intel(R…
