As mentioned in [Greg's answer](
[To see links please register here]
), `mysqldump db_name | mysql new_db_name` is the *free, safe, and easy* way to transfer data between databases. However, it's also *really slow*.
**If you're looking to backup data, can't afford to lose data (in this or other databases), or are using tables other than `innodb`, then you should use `mysqldump`.**
If you're looking for something for development, have all of your databases backed up elsewhere, and are comfortable purging and reinstalling `mysql` (possibly manually) when everything goes wrong, then I might just have the solution for you.
I couldn't find a good alternative, so I built a script to do it myself. I spent *a lot* of time getting this to work the first time and it honestly terrifies me a little to make changes to it now. Innodb databases were not meant to copied and pasted like this. Small changes cause this to fail in magnificent ways. I haven't had a problem since I finalized the code, but that doesn't mean you won't.
Systems tested on (but may still fail on):
- Ubuntu 16.04, default mysql, innodb, separate files per table
- Ubuntu 18.04, default mysql, innodb, separate files per table
*We've since switched to docker and a simple copy of the entire mysql data folder, so this script is no longer maintained. Leaving it in case it's able to help anyone in the future.*
# What it does
1. Gets `sudo` privilege and verifies you have enough storage space to clone the database
2. Gets root mysql privileges
3. Creates a new database named after the current git branch
4. Clones structure to new database
5. Switches into recovery mode for innodb
6. Deletes default data in new database
7. Stops mysql
8. Clones data to new database
9. Starts mysql
10. Links imported data in new database
11. Switches out of recovery mode for innodb
12. Restarts mysql
13. Gives mysql user access to database
14. Cleans up temporary files
# How it compares with `mysqldump`
On a 3gb database, using `mysqldump` and `mysql` would take 40-50 minutes on my machine. Using this method, the same process would only take ~8 minutes.
# How we used it
We had our SQL changes saved alongside our code and the upgrade process is automated on both production and development, with each set of changes making a backup of the database to restore if there's errors. One problem we ran into was when we were working on a long term project with database changes, and had to switch branches in the middle of it to fix a bug or three.
In the past, we used a single database for all branches, and would have to rebuild the database whenever we switched to a branch that wasn't compatible with the new database changes. And when we switched back, we'd have to run the upgrades again.
We tried `mysqldump` to duplicate the database for different branches, but the wait time was too long (40-50 minutes), and we couldn't do anything else in the meantime.
This solution shortened the database clone time to 1/5 the time (think coffee and bathroom break instead of a long lunch).
## Common tasks and their time
Switching between branches with incompatible database changes takes 50+ minutes on a single database, but no time at all after the initial setup time with `mysqldump` or this code. This code just happens to be ~5 times faster than `mysqldump`.
Here are some common tasks and roughly how long they would take with each method:
### Create feature branch with database changes and merge immediately:
- Single database: ~5 minutes
- Clone with `mysqldump`: 50-60 minutes
- Clone with this code: ~18 minutes
### Create feature branch with database changes, switch to `main` for a bugfix, make an edit on the feature branch, and merge:
- Single database: ~60 minutes
- Clone with `mysqldump`: 50-60 minutes
- Clone with this code: ~18 minutes
### Create feature branch with database changes, switch to `main` for a bugfix 5 times while making edits on the feature branch inbetween, and merge:
- Single database: ~4 hours, 40 minutes
- Clone with `mysqldump`: 50-60 minutes
- Clone with this code: ~18 minutes
# The code
**Do not use this unless you've read and understood everything above. It is no longer maintained, so it is more and more likely to be broken as time goes on.**
<!-- language: lang-bash -->
#!/bin/bash
set -e
# This script taken from:
[To see links please register here]
function now {
date "+%H:%M:%S";
}
# Leading space sets messages off from step progress.
echosuccess () {
printf "\e[0;32m %s: %s\e[0m\n" "$(now)" "$1"
sleep .1
}
echowarn () {
printf "\e[0;33m %s: %s\e[0m\n" "$(now)" "$1"
sleep .1
}
echoerror () {
printf "\e[0;31m %s: %s\e[0m\n" "$(now)" "$1"
sleep .1
}
echonotice () {
printf "\e[0;94m %s: %s\e[0m\n" "$(now)" "$1"
sleep .1
}
echoinstructions () {
printf "\e[0;104m %s: %s\e[0m\n" "$(now)" "$1"
sleep .1
}
echostep () {
printf "\e[0;90mStep %s of 13:\e[0m\n" "$1"
sleep .1
}
MYSQL_CNF_PATH='/etc/mysql/mysql.conf.d/recovery.cnf'
OLD_DB='YOUR_DATABASE_NAME'
USER='YOUR_MYSQL_USER'
# You can change NEW_DB to whatever you like
# Right now, it will append the current git branch name to the existing database name
BRANCH=`git rev-parse --abbrev-ref HEAD`
NEW_DB="${OLD_DB}__$BRANCH"
THIS_DIR=./site/upgrades
DB_CREATED=false
tmp_file () {
printf "$THIS_DIR/$NEW_DB.%s" "$1"
}
sql_on_new_db () {
mysql $NEW_DB --unbuffered --skip-column-names -u root -p$PASS 2>> $(tmp_file 'errors.log')
}
general_cleanup () {
echoinstructions 'Leave this running while things are cleaned up...'
if [ -f $(tmp_file 'errors.log') ]; then
echowarn 'Additional warnings and errors:'
cat $(tmp_file 'errors.log')
fi
for f in $THIS_DIR/$NEW_DB.*; do
echonotice 'Deleting temporary files created for transfer...'
rm -f $THIS_DIR/$NEW_DB.*
break
done
echonotice 'Done!'
echoinstructions "You can close this now :)"
}
error_cleanup () {
exitcode=$?
# Just in case script was exited while in a prompt
echo
if [ "$exitcode" == "0" ]; then
echoerror "Script exited prematurely, but exit code was '0'."
fi
echoerror "The following command on line ${BASH_LINENO[0]} exited with code $exitcode:"
echo " $BASH_COMMAND"
if [ "$DB_CREATED" = true ]; then
echo
echonotice "Dropping database \`$NEW_DB\` if created..."
echo "DROP DATABASE \`$NEW_DB\`;" | sql_on_new_db || echoerror "Could not drop database \`$NEW_DB\` (see warnings)"
fi
general_cleanup
exit $exitcode
}
trap error_cleanup EXIT
mysql_path () {
printf "/var/lib/mysql/"
}
old_db_path () {
printf "%s%s/" "$(mysql_path)" "$OLD_DB"
}
new_db_path () {
printf "%s%s/" "$(mysql_path)" "$NEW_DB"
}
get_tables () {
(sudo find /var/lib/mysql/$OLD_DB -name "*.frm" -printf "%f\n") | cut -d'.' -f1 | sort
}
STEP=0
authenticate () {
printf "\e[0;104m"
sudo ls &> /dev/null
printf "\e[0m"
echonotice 'Authenticated.'
}
echostep $((++STEP))
authenticate
TABLE_COUNT=`get_tables | wc -l`
SPACE_AVAIL=`df -k --output=avail $(mysql_path) | tail -n1`
SPACE_NEEDED=(`sudo du -s $(old_db_path)`)
SPACE_ERR=`echo "$SPACE_AVAIL-$SPACE_NEEDED" | bc`
SPACE_WARN=`echo "$SPACE_AVAIL-$SPACE_NEEDED*3" | bc`
if [ $SPACE_ERR -lt 0 ]; then
echoerror 'There is not enough space to branch the database.'
echoerror 'Please free up some space and run this command again.'
SPACE_AVAIL_FORMATTED=`printf "%'d" $SPACE_AVAIL`
SPACE_NEEDED_FORMATTED=`printf "%'${#SPACE_AVAIL_FORMATTED}d" $SPACE_NEEDED`
echonotice "$SPACE_NEEDED_FORMATTED bytes needed to create database branch"
echonotice "$SPACE_AVAIL_FORMATTED bytes currently free"
exit 1
elif [ $SPACE_WARN -lt 0 ]; then
echowarn 'This action will use more than 1/3 of your available space.'
SPACE_AVAIL_FORMATTED=`printf "%'d" $SPACE_AVAIL`
SPACE_NEEDED_FORMATTED=`printf "%'${#SPACE_AVAIL_FORMATTED}d" $SPACE_NEEDED`
echonotice "$SPACE_NEEDED_FORMATTED bytes needed to create database branch"
echonotice "$SPACE_AVAIL_FORMATTED bytes currently free"
printf "\e[0;104m"
read -p " $(now): Do you still want to branch the database? [y/n] " -n 1 -r CONFIRM
printf "\e[0m"
echo
if [[ ! $CONFIRM =~ ^[Yy]$ ]]; then
echonotice 'Database was NOT branched'
exit 1
fi
fi
PASS='badpass'
connect_to_db () {
printf "\e[0;104m %s: MySQL root password: \e[0m" "$(now)"
read -s PASS
PASS=${PASS:-badpass}
echo
echonotice "Connecting to MySQL..."
}
create_db () {
echonotice 'Creating empty database...'
echo "CREATE DATABASE \`$NEW_DB\` CHARACTER SET utf8mb4 COLLATE utf8mb4_unicode_ci" | mysql -u root -p$PASS 2>> $(tmp_file 'errors.log')
DB_CREATED=true
}
build_tables () {
echonotice 'Retrieving and building database structure...'
mysqldump $OLD_DB --skip-comments -d -u root -p$PASS 2>> $(tmp_file 'errors.log') | pv --width 80 --name " $(now)" > $(tmp_file 'dump.sql')
pv --width 80 --name " $(now)" $(tmp_file 'dump.sql') | sql_on_new_db
}
set_debug_1 () {
echonotice 'Switching into recovery mode for innodb...'
printf '[mysqld]\ninnodb_file_per_table = 1\ninnodb_force_recovery = 1\n' | sudo tee $MYSQL_CNF_PATH > /dev/null
}
set_debug_0 () {
echonotice 'Switching out of recovery mode for innodb...'
sudo rm -f $MYSQL_CNF_PATH
}
discard_tablespace () {
echonotice 'Unlinking default data...'
(
echo "USE \`$NEW_DB\`;"
echo "SET foreign_key_checks = 0;"
get_tables | while read -r line;
do echo "ALTER TABLE \`$line\` DISCARD TABLESPACE; SELECT 'Table \`$line\` imported.';";
done
echo "SET foreign_key_checks = 1;"
) > $(tmp_file 'discard_tablespace.sql')
cat $(tmp_file 'discard_tablespace.sql') | sql_on_new_db | pv --width 80 --line-mode --size $TABLE_COUNT --name " $(now)" > /dev/null
}
import_tablespace () {
echonotice 'Linking imported data...'
(
echo "USE \`$NEW_DB\`;"
echo "SET foreign_key_checks = 0;"
get_tables | while read -r line;
do echo "ALTER TABLE \`$line\` IMPORT TABLESPACE; SELECT 'Table \`$line\` imported.';";
done
echo "SET foreign_key_checks = 1;"
) > $(tmp_file 'import_tablespace.sql')
cat $(tmp_file 'import_tablespace.sql') | sql_on_new_db | pv --width 80 --line-mode --size $TABLE_COUNT --name " $(now)" > /dev/null
}
stop_mysql () {
echonotice 'Stopping MySQL...'
sudo /etc/init.d/mysql stop >> $(tmp_file 'log')
}
start_mysql () {
echonotice 'Starting MySQL...'
sudo /etc/init.d/mysql start >> $(tmp_file 'log')
}
restart_mysql () {
echonotice 'Restarting MySQL...'
sudo /etc/init.d/mysql restart >> $(tmp_file 'log')
}
copy_data () {
echonotice 'Copying data...'
sudo rm -f $(new_db_path)*.ibd
sudo rsync -ah --info=progress2 $(old_db_path) --include '*.ibd' --exclude '*' $(new_db_path)
}
give_access () {
echonotice "Giving MySQL user \`$USER\` access to database \`$NEW_DB\`"
echo "GRANT ALL PRIVILEGES ON \`$NEW_DB\`.* to $USER@localhost" | sql_on_new_db
}
echostep $((++STEP))
connect_to_db
EXISTING_TABLE=`echo "SELECT SCHEMA_NAME FROM INFORMATION_SCHEMA.SCHEMATA WHERE SCHEMA_NAME = '$NEW_DB'" | mysql --skip-column-names -u root -p$PASS 2>> $(tmp_file 'errors.log')`
if [ "$EXISTING_TABLE" == "$NEW_DB" ]
then
echoerror "Database \`$NEW_DB\` already exists"
exit 1
fi
echoinstructions "The hamsters are working. Check back in 5-10 minutes."
sleep 5
echostep $((++STEP))
create_db
echostep $((++STEP))
build_tables
echostep $((++STEP))
set_debug_1
echostep $((++STEP))
discard_tablespace
echostep $((++STEP))
stop_mysql
echostep $((++STEP))
copy_data
echostep $((++STEP))
start_mysql
echostep $((++STEP))
import_tablespace
echostep $((++STEP))
set_debug_0
echostep $((++STEP))
restart_mysql
echostep $((++STEP))
give_access
echo
echosuccess "Database \`$NEW_DB\` is ready to use."
echo
trap general_cleanup EXIT
If everything goes smoothly, you should see something like:
[![Screenshot of script output for example database][1]][1]
[1]:
]
