How do I quickly rename a MySQL database (change schema name)?

Question

The MySQL manual at MySQL covers this.

Usually I just dump the database and reimport it with a new name. This is not an option for very big databases. Apparently

Answer 1

Well there are 2 methods:

Method 1: A well-known method for renaming database schema is by dumping the schema using Mysqldump and restoring it in another schema, and then dropping the old schema (if needed).

From Shell

 mysqldump emp > emp.out
 mysql -e "CREATE DATABASE employees;"
 mysql employees < emp.out 
 mysql -e "DROP DATABASE emp;"

Although the above method is easy, it is time and space consuming. What if the schema is more than a 100GB? There are methods where you can pipe the above commands together to save on space, however it will not save time.

To remedy such situations, there is another quick method to rename schemas, however, some care must be taken while doing it.

Method 2: MySQL has a very good feature for renaming tables that even works across different schemas. This rename operation is atomic and no one else can access the table while its being renamed. This takes a short time to complete since changing a table’s name or its schema is only a metadata change. Here is procedural approach at doing the rename:

Create the new database schema with the desired name. Rename the tables from old schema to new schema, using MySQL’s “RENAME TABLE” command. Drop the old database schema. If there are views, triggers, functions, stored procedures in the schema, those will need to be recreated too. MySQL’s “RENAME TABLE” fails if there are triggers exists on the tables. To remedy this we can do the following things :

1) Dump the triggers, events and stored routines in a separate file. This done using -E, -R flags (in addition to -t -d which dumps the triggers) to the mysqldump command. Once triggers are dumped, we will need to drop them from the schema, for RENAME TABLE command to work.

 $ mysqldump  -d -t -R -E > stored_routines_triggers_events.out

2) Generate a list of only “BASE” tables. These can be found using a query on information_schema.TABLES table.

 mysql> select TABLE_NAME from information_schema.tables where 
    table_schema='' and TABLE_TYPE='BASE TABLE';

3) Dump the views in an out file. Views can be found using a query on the same information_schema.TABLES table.

mysql> select TABLE_NAME from information_schema.tables where 
   table_schema='' and TABLE_TYPE='VIEW';
 $ mysqldump    … > views.out

4) Drop the triggers on the current tables in the old_schema.

mysql> DROP TRIGGER ;
...

5) Restore the above dump files once all the “Base” tables found in step #2 are renamed.

mysql> RENAME TABLE .table_name TO .table_name;
...
$ mysql  < views.out
$ mysql  < stored_routines_triggers_events.out

Intricacies with above methods : We may need to update the GRANTS for users such that they match the correct schema_name. These could fixed with a simple UPDATE on mysql.columns_priv, mysql.procs_priv, mysql.tables_priv, mysql.db tables updating the old_schema name to new_schema and calling “Flush privileges;”. Although “method 2″ seems a bit more complicated than the “method 1″, this is totally scriptable. A simple bash script to carry out the above steps in proper sequence, can help you save space and time while renaming database schemas next time.

The Percona Remote DBA team have written a script called “rename_db” that works in the following way :

[root@dba~]# /tmp/rename_db
rename_db   

To demonstrate the use of this script, used a sample schema “emp”, created test triggers, stored routines on that schema. Will try to rename the database schema using the script, which takes some seconds to complete as opposed to time consuming dump/restore method.

mysql> show databases;
+--------------------+
| Database           |
+--------------------+
| information_schema |
| emp                |
| mysql              |
| performance_schema |
| test               |
+--------------------+


[root@dba ~]# time /tmp/rename_db localhost emp emp_test
create database emp_test DEFAULT CHARACTER SET latin1
drop trigger salary_trigger
rename table emp.__emp_new to emp_test.__emp_new
rename table emp._emp_new to emp_test._emp_new
rename table emp.departments to emp_test.departments
rename table emp.dept to emp_test.dept
rename table emp.dept_emp to emp_test.dept_emp
rename table emp.dept_manager to emp_test.dept_manager
rename table emp.emp to emp_test.emp
rename table emp.employees to emp_test.employees
rename table emp.salaries_temp to emp_test.salaries_temp
rename table emp.titles to emp_test.titles
loading views
loading triggers, routines and events
Dropping database emp

real    0m0.643s
user    0m0.053s
sys     0m0.131s


mysql> show databases;
+--------------------+
| Database           |
+--------------------+
| information_schema |
| emp_test           |
| mysql              |
| performance_schema |
| test               |
+--------------------+

As you can see in the above output the database schema “emp” was renamed to “emp_test” in less than a second. Lastly, This is the script from Percona that is used above for “method 2″.

#!/bin/bash
# Copyright 2013 Percona LLC and/or its affiliates
set -e
if [ -z "$3" ]; then
    echo "rename_db   "
    exit 1
fi
db_exists=`mysql -h $1 -e "show databases like '$3'" -sss`
if [ -n "$db_exists" ]; then
    echo "ERROR: New database already exists $3"
    exit 1
fi
TIMESTAMP=`date +%s`
character_set=`mysql -h $1 -e "show create database $2\G" -sss | grep ^Create | awk -F'CHARACTER SET ' '{print $2}' | awk '{print $1}'`
TABLES=`mysql -h $1 -e "select TABLE_NAME from information_schema.tables where table_schema='$2' and TABLE_TYPE='BASE TABLE'" -sss`
STATUS=$?
if [ "$STATUS" != 0 ] || [ -z "$TABLES" ]; then
    echo "Error retrieving tables from $2"
    exit 1
fi
echo "create database $3 DEFAULT CHARACTER SET $character_set"
mysql -h $1 -e "create database $3 DEFAULT CHARACTER SET $character_set"
TRIGGERS=`mysql -h $1 $2 -e "show triggers\G" | grep Trigger: | awk '{print $2}'`
VIEWS=`mysql -h $1 -e "select TABLE_NAME from information_schema.tables where table_schema='$2' and TABLE_TYPE='VIEW'" -sss`
if [ -n "$VIEWS" ]; then
    mysqldump -h $1 $2 $VIEWS > /tmp/${2}_views${TIMESTAMP}.dump
fi
mysqldump -h $1 $2 -d -t -R -E > /tmp/${2}_triggers${TIMESTAMP}.dump
for TRIGGER in $TRIGGERS; do
    echo "drop trigger $TRIGGER"
    mysql -h $1 $2 -e "drop trigger $TRIGGER"
done
for TABLE in $TABLES; do
    echo "rename table $2.$TABLE to $3.$TABLE"
    mysql -h $1 $2 -e "SET FOREIGN_KEY_CHECKS=0; rename table $2.$TABLE to $3.$TABLE"
done
if [ -n "$VIEWS" ]; then
    echo "loading views"
    mysql -h $1 $3 < /tmp/${2}_views${TIMESTAMP}.dump
fi
echo "loading triggers, routines and events"
mysql -h $1 $3 < /tmp/${2}_triggers${TIMESTAMP}.dump
TABLES=`mysql -h $1 -e "select TABLE_NAME from information_schema.tables where table_schema='$2' and TABLE_TYPE='BASE TABLE'" -sss`
if [ -z "$TABLES" ]; then
    echo "Dropping database $2"
    mysql -h $1 $2 -e "drop database $2"
fi
if [ `mysql -h $1 -e "select count(*) from mysql.columns_priv where db='$2'" -sss` -gt 0 ]; then
    COLUMNS_PRIV="    UPDATE mysql.columns_priv set db='$3' WHERE db='$2';"
fi
if [ `mysql -h $1 -e "select count(*) from mysql.procs_priv where db='$2'" -sss` -gt 0 ]; then
    PROCS_PRIV="    UPDATE mysql.procs_priv set db='$3' WHERE db='$2';"
fi
if [ `mysql -h $1 -e "select count(*) from mysql.tables_priv where db='$2'" -sss` -gt 0 ]; then
    TABLES_PRIV="    UPDATE mysql.tables_priv set db='$3' WHERE db='$2';"
fi
if [ `mysql -h $1 -e "select count(*) from mysql.db where db='$2'" -sss` -gt 0 ]; then
    DB_PRIV="    UPDATE mysql.db set db='$3' WHERE db='$2';"
fi
if [ -n "$COLUMNS_PRIV" ] || [ -n "$PROCS_PRIV" ] || [ -n "$TABLES_PRIV" ] || [ -n "$DB_PRIV" ]; then
    echo "IF YOU WANT TO RENAME the GRANTS YOU NEED TO RUN ALL OUTPUT BELOW:"
    if [ -n "$COLUMNS_PRIV" ]; then echo "$COLUMNS_PRIV"; fi
    if [ -n "$PROCS_PRIV" ]; then echo "$PROCS_PRIV"; fi
    if [ -n "$TABLES_PRIV" ]; then echo "$TABLES_PRIV"; fi
    if [ -n "$DB_PRIV" ]; then echo "$DB_PRIV"; fi
    echo "    flush privileges;"
fi