Workflow [PR], commit [d0e8ec2]

S3 fails: Altinity/clickhouse-regression#93

Aggregate fails: uniqTheta was updated in upstream, not related, test will be updated separately by QA team

QA Verification

Analysis Summary

This PR is a backport of upstream ClickHouse#87303 (with follow-ups ClickHouse#88017 and ClickHouse#88036) to the releases/25.8.15 branch.

Bug Fixed:

The move-to-PREWHERE optimization did not work when row policies were present, causing performance degradation. This fix restructures how row-level filtering interacts with PREWHERE optimization.

New Tests:

• 03591_optimize_prewhere_row_policy.sql - Verifies PREWHERE optimization works with row policies
• 03641_analyzer_issue_85834.sql - Regression test for issue Not found column when combining row policies, prewhere and additional_table_filters ClickHouse/ClickHouse#85834

Verification Criteria:

*Remaining Failures:

Regression Tests

• S3/*/zero copy replication
  Regression in zero-copy replication introduced in 25.8.15.
  Issue Regression: S3 zero-copy replication leaves replica out of sync in 25.8.15 #1338 was opened and the fix was made upstream.
  Once it is backported, these regression tests will pass.

• /aggregate functions/part 1/uniqTheta
  Failure caused by an upstream bug fix that changed the expected result.
  Snapshots were already updated in Altinity/clickhouse-regression to reflect the correct behavior.
  Failure: RegressionTestsRelease /aggregate functions/part 1/uniqTheta - snapshot outdated clickhouse-regression#96
  After updating the commit hash, this test will pass.

Integration Tests

• test_async_load_databases/test.py::test_materialized_views_cascaded_multiple
  Flaky upstream integration test caused by a race condition in materialized view processing order after server restart, leading to incorrect data (42,0 instead of 42,2).
  Upstream issue ClickHouse#88572 was fixed in PR 88573, but the fix was not backported to 25.8.
  This test fails frequently on upstream 25.8 sanitizer builds (~14.1%).
  Marked as known flaky test in tests/broken_tests.yaml for 25.8.

• test_async_load_databases/test.py::test_materialized_views_replicated
  Flaky upstream integration test that fails with "Database test_mv already exists" due to missing cleanup from the previous test (test_materialized_views_cascaded_multiple).
  Both tests fail together as a pair and share the same root cause and upstream fix (ClickHouse#88573), not backported to 25.8.
  This test also fails frequently on upstream 25.8 sanitizer builds (~14.1%).
  Marked as known flaky test in tests/broken_tests.yaml for 25.8.

Notes:

• Large structural change (54 files) but well-tested upstream
• Includes backport-specific fix commit.
• Comprehensive EXPLAIN-based tests verify correct query plan generation

No manual testing required - upstream validation, follow-up fixes, and CI coverage are sufficient for this backport.
Adding verified label.