enable_optimize_predicate_expression_* session settings

These settings are available in system.settings and are autogenerated from source.

enable_optimize_predicate_expression

Turns on predicate pushdown in SELECT queries. Predicate pushdown may significantly reduce network traffic for distributed queries. Possible values:

0 — Disabled.
1 — Enabled.

Usage Consider the following queries:

SELECT count() FROM test_table WHERE date = '2018-10-10'
SELECT count() FROM (SELECT * FROM test_table) WHERE date = '2018-10-10'

If enable_optimize_predicate_expression = 1, then the execution time of these queries is equal because ClickHouse applies WHERE to the subquery when processing it. If enable_optimize_predicate_expression = 0, then the execution time of the second query is much longer because the WHERE clause applies to all the data after the subquery finishes.

enable_optimize_predicate_expression_to_final_subquery

Allow push predicate to final subquery.

SQL Reference

Data Types

Engines

Functions

Formats

Settings

System Tables

Data Lakes

enable_optimize_predicate_expression_* session settings