Zonemaps

Detail name	Value
Changelog Number	17131
Type	New Feature
Status	Resolved
Fix Versions	Exasol 8.18.0
Resolution Date	2023-05-25

New Feature

Zonemaps is a new feature introducing a metadata layer to the table which is useful for speeding up filtering in queries.

It is automatically enabled for partitioned columns (for supported data types). During migration to version 8, tables with partitioning will have the Zonemaps enabled by default. (this may take some time depending on the contents of the table).

For more information on Zonemaps, see Zonemaps.

SQL Syntax

Zonemaps can be manually enabled or disabled for any column of supported data type using the ENFORCE ZONEMAP and DROP ZONEMAP syntax:

{{ENFORCE ZONEMAP on myTable (ColA); }}
DROP ZONEMAP on myTable (ColA);

System Tables

The presence of a zonemap can be found by checking the {{EXA_

_COLUMNS}} table with the column COLUMN_IS_ZONEMAPPED. Another way to find out is to use the [DESCRIBE|https://docs.exasol.com/db/latest/sql/desc[ribe].htm] command and check the ZONEMAPPED column.

Whether or not a zonemap was used for speeding up query filtering can be found in profiling tables. When a zonemap is used, the PART_INFO column contains WITH ZONEMAP

Changed behavior

Added support for zonemaps on partitioned columns. New SQL Syntax ENFORCE ZONEMAP and DROP ZONEMAP