Disadvantages of Compressionn


Disadvantages of Compressionn

Hi Experts ,

What are the disadvantages of compression . Especially is there any scenario when compressed column create an issue while joining with another table and uncompressed column .

Thanks in advance for your reply  .


Re: Disadvantages of Compressionn

It can increase CPU usage.  A trade-off is to be made with IO.

Re: Disadvantages of Compressionn

Thanks a lot Raja .
Teradata Employee

Re: Disadvantages of Compressionn

Depends on which compression you are asking about...

All compression forms on Teradata have no impact on users and creates no limitations on joining, comparing, accessing, returning or any other operation on a column. All forms are invisible to the query user.

Multi Value Compression has no CPU overhead. The only tradeoff of MVC is that analysis needs to be performed to determine the values and then add them to the DDL of the column.

Algorithmic column compression also needs to be defined as a column DDL option. It has a CPU cost but only when accessing the column.

Block compression has a significant CPU cost. In general it should be used selectively on large tables that are accessed less frequently. A frequently accessed table will cause high CPU utilization to repeatedly decompress the data. This can be defined specifically at the table level or the system can be enabled to compress the least frequently used data automatically.