I'm trying to reverse a date type index on a InnoDB database schema via. MySQL Workbench
But every time i try to apply the changes they are ignored?
Do i need to use the command line to configure the database?
According to http://www.oracle.com/partners/en/knowledge-zone/mysql-5-5-innodb-myisam-522945.pdf
Page 10. InnoDB supports BTREE indexes.
Related
Why does phpMyAdmin show an empty cardinality?
If I edit the index (without change anything) and save, the cardinality will appear, but after a TRUNCATE and some INSERTs, the cardinality become empty again.
Running
ALTER TABLE tableName ENABLE KEYS
doesn't help.
How to make the cardinality always present?
Edit:
The phpMyAdmin version is 4.6.4
The MySql version is libmysql - mysqlnd 5.0.12-dev - 20150407
The Engine is MyISAM
You need to analyze the table.
ANALYZE LOCAL TABLE tablename
The stats for the primary key are updated when the data is updated, but the other indexes need this operation to set a value. Note that if the distribution of the data is not changing then you don't need to refresh the indexes.
Note that there is a performance impact (and locking impact with MyISAM) on large tables when you run this.
Aha -- I found NULLs with SHOW INDEXES on a MyISAM table. Is yours ENGINE=MyISAM? Recommend changing to InnoDB.
I have a set of servers where the maintenance query execution takes long. This is due to the indexes that are created by the developers at different points. Is there any way to monitor the unused indexes that adversely affect the execution.
For mysql 5.6 before
By Default package of mysql does not have much statistics for analysis but there are some unofficial patches by which you can analyze.
like userstats http://ourdelta.org/docs/userstats
By This patch you can analyze the stats and unused indexes.
Follow the below links to do that
https://www.percona.com/blog/2012/06/30/find-unused-indexes/
In MySQL 5.6 and later, the PERFORMANCE_SCHEMA tracks index IO. If an index has no IO activity, it has not been used.
The sys schema now provides a convenient view to make it easier to identify unused indexes:
http://www.markleith.co.uk/2011/04/18/monitoring-table-and-index-io-with-performance_schema/
DROP VIEW IF EXISTS unused_indexes;
CREATE VIEW unused_indexes AS
SELECT object_schema,
object_name,
index_name
FROM performance_schema.table_io_waits_summary_by_index_usage
WHERE index_name IS NOT NULL
AND count_star = 0
ORDER BY object_schema, object_name;
Note that this shows indexes that haven't been used since the last restart of mysqld. The PERFORMANCE_SCHEMA statistics are reset at startup time.
For MySQL version 5.7 and later, you can SYS schema to retrieve data either in raw format of user understandable format. SYS schema fetch the data from the underlying performance_schema and information_schema and present them in a better, understandable format. Refer here
I am running MySQL 5.6.13 and I would like to run a CREATE INDEX ... BTREE statement on my production database.
The table is InnoDB and has ~ 4 million rows, and I would like very much not to lock it.
According to the docs, it appears as if this statement will not completely lock my table and return quickly. But, I wanted a second opinion before I made this change.
Would it be safe to create this index?
By default, InnoDB in MySQL 5.6 will perform a read lock while creating the index, so you can still have other concurrent clients SELECT from the table, but not do insert/update/delete on that table while the index is being created.
You can optionally allow the index creation to be completely online and not even do the read lock:
ALTER TABLE my_table ADD INDEX a (a), LOCK=NONE;
See http://dev.mysql.com/doc/refman/5.6/en/innodb-create-index-overview.html for more details about online DDL statements in MySQL.
Also see this blog posted today from a MySQL Community Manager: Top 10 advances to availability since MySQL 5.5
PS: It's not necessary to specify BTREE for the index type. InnoDB supports only BTREE indexes, so it ignores that option.
I have MySQL running on my machine configured with MyISAM as its default tables.
Now I want to ask few of questions:
1) If I change the default table to InnoDB in the configuration file (my.conf), clear the log file and restart mysql, would that harm any of my previous database or tables?
2) If I alter few tables' engine to InnoDB using the following command, would that affect its data at all?
ALTER TABLE table_name ENGINE = InnoDB;
3) Is it a good idea to keep few tables as MyISAM (for read and write) and the rest as InnoDB (more for selecting data) or is it preferred to select one engine for all the tables in the database?
2) It will only affect the internal representation. Nothing that you will notice on the outside.
3) It is a perfectly good idea, if it enhances performance.
2) You can mix database types. i.e. innoDB and MyISAM.
3) innoDB supposedly keeps data safer. I think it is the default on latest versions of mySQL.
I’m trying to create a FULLTEXT index on an attribute of a table. Mysql returns
ERROR 1214: The used table type doesn’t support FULLTEXT indexes.
Any idea what I’m doing wrong?
You’re using the wrong type of table. Mysql supports a few different types of tables, but the most commonly used are MyISAM and InnoDB. MyISAM (in MySQL 5.6+also InnoDB tables) are the types of tables that Mysql supports for Full-text indexes.
To check your table’s type issue the following sql query:
SHOW TABLE STATUS
Looking at the result returned by the query, find your table and corresponding value in the Engine column. If this value is anything except MyISAM or InnoDB then Mysql will throw an error if your trying to add FULLTEXT indexes.
To correct this, you can use the sql query below to change the engine type:
ALTER TABLE <table name> ENGINE = [MYISAM | INNODB]
Additional information (thought it might be useful):
Mysql using different engine storage types to optimize for the needed functionality of specific tables. Example MyISAM is the default type for operating systems (besides windows), preforms SELECTs and INSERTs quickly; but does not handle transactions. InnoDB is the default for windows, can be used for transactions. But InnoDB does require more disk space on the server.
Up until MySQL 5.6, MyISAM was the only storage engine with support for full-text search (FTS) but it is true that InnoDB FTS in MySQL 5.6 is syntactically identical to MyISAM FTS. Please read below for more details.
InnoDB Full-text Search in MySQL 5.6
On MySQL <= 5.5, the mysql manual says that FULLTEXT indexes can only be created on tables with the mylsam engine.
Are you using InnoDB? The only table type that supports FULLTEXT is MyISAM.
apart from MyISAM table PARTITIONING also not support full-text index.