… compression which makes its indexes much smaller, allowing better fit in caches and so improving performance dramatically. Actually packed indexes not a bit… stored in the index even if it is not packed. Compressed blocks need to be treated differently. For uncompressed index blocks MySQL can do…` (`c`), KEY `id` (`id`) ) ENGINE=MyISAM Index size: PACK_KEYS=DEFAULT – 1550K PACK_KEYS=1 – 1453K PACK_KEYS=0 – 8176K As we can see…
Post: Index Condition Pushdown in MySQL 5.6 and MariaDB 5.5 and its performance impact
March 12, 2012 By 12 Comments
… is aimed at a new optimizer enhancement Index Condition Pushdown (ICP). Its available in both MySQL 5.6 and MariaDB 5.5… is, and what is it aimed at. Index Condition Pushdown Traditional B-Tree index lookups have some limitations in cases such as range scans, where index parts after the part on which range condition is applied…
Post: Why MySQL could be slow with large tables ?
June 9, 2006 By 141 Comments
… benefit from using indexes. In fact even MySQL optimizer currently does not take it into account. For In memory workload index accesses might….000.000 rows per second for fully sequential access, jam packed rows – quite possible scenario for MyISAM tables. Now if we… scan by index: mysql> select count(pad) from large; +————+ | count(pad) | +————+ | 31457280 | +————+ 1 row in set (4 min 58.63 sec) mysql> select…
Post: Descending indexing and loose index scan
May 9, 2006 By 6 Comments
… – these are features MySQL should get for all storage engines at some point. Descending indexes – This is something MySQL does not have at… a bit. Or some storage engines, such as MyISAM (for packed indexes) may have reverse scan being much slower than forward scan… databases. Designing the indexes for MySQL you should only make sure queries use “=” for all keyparts in the last of index. Only last…
Post: Concatenating MyISAM files
November 19, 2012 By 5 Comments
… of a large read-only InnoDB database to MyISAM (eventually packed). The only issue was that for one of the table…’ Data records: 3 – Fixing index 1 Data records: 6 And then, back in mysql: mysql> use test Database changed mysql> flush tables; Query OK…:/var/lib/mysql/test# myisamchk -r test_concat – recovering (with sort) MyISAM-table ‘test_concat’ Data records: 6 – Fixing index 1 mysql> select…
Post: How is join_buffer_size allocated?
July 5, 2010 By 9 Comments
…MySQL configuration, we quite often want to know… — it has to, because there’s no index. If the query joins several tables this way… source: 14176 /***************************************************************************** 14177 Fill join cache with packed records 14178 Records are stored in tab->…
Post: ANALYZE: MyISAM vs Innodb
September 3, 2008 By 9 Comments
… 0 mysql> show index from antest; +——–+————+———-+————–+————-+———–+————-+———-+——–+——+————+———+ | Table | Non_unique | Key_name | Seq_in_index | Column_name | Collation | Cardinality | Sub_part | Packed | Null | Index_type…
Comment: To pack or not to pack - MyISAM Key compression
November 2, 2012 By 4 Comments
… about 4MB index. But I find not obvious performance increasement. That is when I became confused about the introduction of MySQL, saying…, that you said “Be careful with PACK_KEYS=0 as it can blow up your index size 10x times.”, I think this…, whose index declines when PACK_KEYS=0(changed from DEFAULT). MyISAM seems to set a limit to the mixinum of index data, in…
Comment: ORDER BY ... LIMIT Performance Optimization
November 17, 2009 By 100 Comments
… my indexes are set:- mysql> show index from follow; +——–+————+———-+————–+————–+———–+————-+———-+——–+——+————+———+ | Table | Non_unique | Key_name | Seq_in_index | Column_name | Collation | Cardinality | Sub_part | Packed…
Comment: Quick comparison of MyISAM, Infobright, and MonetDB
September 30, 2009 By 30 Comments
… updating the database from replication. I get that from InnoDB+MySQL minus the support for fast DW queries. I don’t… an index that stores the min,max per column for each block of a database file (data packs or data pack nodes in… aggregated values per data pack. Monty also spoke at the MySQL Conference about this and called it ‘XDB indexes‘. I hope a standard…
