2012/2/28 Hontvári József Levente <hontv...@flyordie.com> > > >> * Does the column name get stored for every col/val for every key (which >> sort of worries me for long column names) >> > > Yes, the column name is stored with each value for every key, but it may > not matter if you switch on compression, which AFAIK has only advantages > and will be the default. I am also worried about the storage space, so I > did a test. >
Yes - I'm using compression - I've seen the same outcome in one of our own systems. > > There is a MySQL table which I intend to move to Cassandra. It has about > 40 columns with very long column names, the average is 15 characters. The > column values are mostly 2-4 byte integers. On the other hand many colums > are empty, specifically not NULL but 0. AFAIK MySQL is also able to > optimize NON NULL columns with 0 values to a single bit. In Cassandra I > simply did not store a column if its value is the default 0. The table > size, only data without indexes, in MySQL was about 2.5 GB with 7 millions > rows. In Cassandra it was about 12 GB without compression, and 3,4 GB with > compression (which also includes a single index for the row keys). > > So with compression switched on, in this specific case the storage > requirements are roughly the same on Cassandra and MySQL. Good to know - thanks > > > > > >> * Is data in an sstable sorted by key then column or column then key >> >> > Sorted by key and then sorted by column. > > > thanks -- *Franc Carter* | Systems architect | Sirca Ltd <marc.zianideferra...@sirca.org.au> franc.car...@sirca.org.au | www.sirca.org.au Tel: +61 2 9236 9118 Level 9, 80 Clarence St, Sydney NSW 2000 PO Box H58, Australia Square, Sydney NSW 1215
