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Question and Answer

Connor McDonald

Thanks for the question, Berton.

Asked: August 10, 2020 - 2:01 pm UTC

Answered by: Connor McDonald - Last updated: August 13, 2020 - 3:09 am UTC

Category: Database Administration - Version: 12.1

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You Asked

We have quite a few very large tables that are interval partitioned ( 1 partition per day ). At any given point we store 120 days worth of data, i.e. we do daily partition maintenance and move the > 120 days data over to either Archival systems or purge them.

My question is, is it possible to compress new partitions as they are added to the source table or do we need to create a new table and move data ?

Here is an example of what the source table looks like

create table my_very_large_table
  id                        number(20) not null,
  processedxml              clob,
  updatedon                 date default trunc( current_date )
lob ( processedxml ) store as securefile 
   tablespace my_tablespace
   enable storage in row chunk 8192
partition by range( updatedon )
interval( numtodsinterval( 1, 'day' ))
   partition p_default values less than ( to_date( '01/01/2020', 'mm/dd/yyyy' ))
tablespace my_tablespace;

We have 120 days worth of data in this table and several hundred thousand rows are added everyday. Can I alter the partition attributes so that new partitions are created as compressed ?



and we said...

You can alter the *default* settings for a table (for new partitions), eg

alter table my_partitioned_table modify default attributes compress for all operations 

and you rated our response

  (1 rating)


compress on lobs.

August 13, 2020 - 5:21 am UTC

Reviewer: Rajeshwaran, Jeyabal

But given this very skinny table of three columns, we suspect the bunch of data will be in lob segments.

so it is worth to benchmark by compressing the lob segments and measure the benefits.

since you are using secure files, de-duplication is also possible. please do check that too.

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