I have had recently the need to backup a big database (more than 250GB uncompressed dump file) and I found the answers to this question really helpful.
I started using @Trutane approach and it worked like a charm. But I was concerned about dumping tables in different mysql sessions because that could, in some moment, drive to a non-consistent backup.
After some research and testing, I have developed a different solution based on gawk
. The basic idea is creating a dump of the whole database using mysqldump
with --single-transaction=true
and then process the output with gawk
to produce a different file for every table.
So I can call:
mysqldump --single-transaction=true -u DBUSERNAME -p DBNAME | \
gawk -v 'database=DBNAME' -f 'backup.awk' -
And it produces, in current folder, a bunch of $database.$table.sql
files with the schema of every table and $database.$table.sql.gz
files with the content of every table. Thanks to the param --single-transaction=true
, all the dump happens in a single transaction and data consistency is ensured.
The content of backup.awk
is:
# Split mysqldump output in different files, two per table:
# * First file is named $database.$table.sql and it contains the table schema
# * Second file is named $database.$table.sql.gz and it contains the table data
# The 'database' variable is expected to be provided in command-line
BEGIN {
insert=0
filename=sprintf("%s.header.sql", database);
}
# A line starting with "INSERT INTO" activates inserting mode
/^INSERT INTO/ { insert=1 }
# A line containing "-- Table structure for table `name-of-table`" finishes inserting mode
# It is also used to detect table name and change file names accordingly
match($0, /-- Table structure for table `(.*)`/, m) {
insert=0;
table=m[1];
filename=sprintf("%s.%s.sql", database, table);
print sprintf("Dumping table %s", table);
}
# If in inserting mode, line is piped to a gzipped file,
# if it is not, it is redirected to an uncompressed schema file
{
if (insert == 1) {
output = sprintf("gzip > %s.gz", filename);
print | output
} else {
print > filename;
}
}