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Documentation Index

Fetch the complete documentation index at: https://private-7c7dfe99-page-updates.mintlify.app/llms.txt

Use this file to discover all available pages before exploring further.

The following operations are available:
  • ALTER TABLE [db].table ADD STATISTICS [IF NOT EXISTS] (column list) TYPE (type list) - Adds statistic description to tables metadata.
  • ALTER TABLE [db].table MODIFY STATISTICS (column list) TYPE (type list) - Modifies statistic description to tables metadata.
  • ALTER TABLE [db].table DROP STATISTICS [IF EXISTS] (column list) - Removes statistics from the metadata of the specified columns and deletes all statistics objects in all parts for the specified columns.
  • ALTER TABLE [db].table CLEAR STATISTICS [IF EXISTS] (column list) - Deletes all statistics objects in all parts for the specified columns. Statistics objects can be rebuild using ALTER TABLE MATERIALIZE STATISTICS.
  • ALTER TABLE [db.]table MATERIALIZE STATISTICS (ALL | [IF EXISTS] (column list)) - Rebuilds the statistic for columns. Implemented as a mutation.
The first two commands are lightweight in a sense that they only change metadata or remove files. Also, they are replicated, syncing statistics metadata via ZooKeeper.

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Example:

Adding two statistics types to two columns: 
ALTER TABLE t1 MODIFY STATISTICS c, d TYPE TDigest, Uniq;
Adding NullCount statistics to a Nullable column: 
ALTER TABLE t1 ADD STATISTICS nullable_col TYPE NullCount;
Statistic are supported only for *MergeTree engine tables (including replicated variants).