Technical Exasol

How to use Exasol’s Automatic Table Reorganization

17 Sep 2019 | Share

Exasol Blog - How to use Exasol's Automatic Table Reorganization

One of Exasol’s key features is the low maintenance effort when compared to many other database systems. Automatic Table Reorganization is one example:

Exasol offers CREATE OR REPLACE TABLE and the DELETE_PERCENTAGE is zero after the table is created. The TABLE_ROW_COUNT is maintained automatically after each data manipulation language (DML) – there’s no need to gather statistics.

10% of rows are marked as deleted for this table but not yet removed. Let’s delete another 100,000 rows and see what happens.

Now 20% of rows are marked as deleted. There’s a threshold of 25% deleted rows that triggers an automatic reorganization:

DELETE_PERCENTAGE resets to zero because of the automatic reorganization – I didn’t have to do anything.

By the way, if INSERTS follows the DELETE, the DELETE_PERCENTAGE decreases automatically too as the space used by the rows marked as deleted is used.

Reorganization can be done manually too:

Uwe Blog Code 6

A manual reorganization is possible but usually isn’t necessary. Typically, reorganization is only needed after the Exasol cluster has been enlarged by adding one or more nodes.

10 trends impacting data analytics

Now that we’re well and truly in the age of data, what’s coming next?