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From onmstester onmstester <>
Subject Re: data types storage saving
Date Sat, 10 Mar 2018 08:07:22 GMT
Anyway, I cant get to a approximate method to calculate storage per row for Cassandra records.

For example right now my table schema is as follow:

c1 tinyint,

c2 smallint,

c3 bigint,

c4 int,

c5 int,

c6 boolean

primary key ((c1,c2,c3),c4,c5)
According to cql data types document this should allocate like 23 bytes per record from my
storage but in real experiments turns out that it uses like 70 bytes per record and compression
ratio reported from cfstats is like 0.45... so it actually uses like 140 bytes per row if
there was no compression.

 Why this much storage overhead? How could i calculate disk usage approximately(without inserting
actual data)?

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---- On Sat, 10 Mar 2018 11:21:44 +0330 onmstester onmstester &lt;;
wrote ----

I've find out that blobs has no gain in storage saving!

I had some 16 digit number which been saved as bigint previously but by saving this as blob,
the storage usage per record is still the same

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---- On Tue, 06 Mar 2018 19:18:31 +0330 Carl Mueller &lt;;
wrote ----

If you're willing to do the data type conversion in insert and retrieval, the you could use
blobs as a sort of "adaptive length int" AFAIK

On Tue, Mar 6, 2018 at 6:02 AM, onmstester onmstester &lt;;

I'm using int data type for one of my columns but for 99.99...% its data never would be &gt;
65K, Should i change it to smallint (It would save some Gigabytes disks in a few months) or
Cassandra Compression would take care of it in storage? 

What about blob data type ? Isn't  better to use it in such cases? could i alter column type
from smallInt to int in future if needed?

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