Monthly Archives - May 2009

Clustering indexes vs. Covering indexes

Yesterday, I (Zardosht) posted an entry introducing clustering indexes. Here, I elaborate on three differences between a clustering index and a covering index:

Clustering indexes can create indexes that would otherwise bounce up against the limits on the maximum length and maximum number of columns in a MySQL index.
Clustering indexes simplify syntax making them […]

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Hint: throttling xtrabackup

Using xtrabackup for copying files can really saturate your disks, and that why we made special option

Shell

–throttle=rate

1

–throttle=rate

to limit rate of IO per second. But it really works when you do local copy.
What about stream backup ? Even you copy just to remote box with

Shell

innobackupex –stream=tar | ssh remotebox “tar xfi -”

1

innobackupex –stream=tar […]

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What time 18446744073709550.000 means

Sometimes when you do profiling you can see number like this in timestamps. Periodically in our patches there was Query_time: 18446744073709550.000 in slow.log file (well, it was fixed recently, but still appears in other places).
I faced this problem several years ago when only 2-core AMD Opteron systems appeared and I noticed sysbench getting […]

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