fix(schema-compiler): Use isNotDistinctFrom() for ClickHouse Tesseract multi-fact joins

[rclapp]

Summary

• Fixes ClickHouse Tesseract multi-fact queries failing with Cannot determine join keys in JOIN ON expression error
• Adds support for a function-style expressions/is_not_distinct_from template as a fallback when the binary operator operators/is_not_distinct_from is not available
• Registers ClickHouse's isNotDistinctFrom(left, right) function via the new expression template

Fixes #10493

Context

When CUBEJS_TESSERACT_SQL_PLANNER=true is enabled, multi-fact queries (measures from multiple cubes) generate null-safe JOIN conditions using OR (IS NULL AND IS NULL):

ON ((a.col = b.col OR ((a.col IS NULL) AND (b.col IS NULL))))

ClickHouse rejects this — it requires simple equality or function calls in JOIN ON clauses.

Other dialects (Postgres, BigQuery, Snowflake) use the IS NOT DISTINCT FROM binary operator, but ClickHouse's equivalent is the function isNotDistinctFrom(a, b) — not a binary operator. The existing operators/is_not_distinct_from template only supports binary operator syntax via the expressions/binary template ({{ left }} {{ op }} {{ right }}).

Changes

Rust (rust/cubesqlplanner/cubesqlplanner/src/planner/sql_templates/plan.rs):

• Added supports_is_not_distinct_from_expr() check for expressions/is_not_distinct_from template
• In join_by_dimension_conditions(), added fallback path: check binary operator first, then expression template, then existing OR (IS NULL AND IS NULL) fallback

TypeScript (packages/cubejs-schema-compiler/src/adapter/ClickHouseQuery.ts):

• Registered expressions.is_not_distinct_from = 'isNotDistinctFrom({{ left }}, {{ right }})' in sqlTemplates()

This is minimally invasive — existing dialects continue using the operators/is_not_distinct_from binary operator path unchanged.

Check List

• Tests have been run in packages where changes have been made if available
• Linter has been run for changed code
• Tests for the changes have been added if not covered yet
• Docs have been added / updated if required

Test results

Rust (cargo test): 373 passed, 0 failed (368 existing + 5 new)
Rust (cargo fmt --check): No formatting issues

New unit tests (plan::tests::test_join_condition_*):

• test_join_condition_no_null_check — simple equality without null handling
• test_join_condition_null_check_fallback_or_is_null — OR/IS NULL fallback (no templates)
• test_join_condition_null_check_binary_operator — Postgres/BigQuery/Snowflake path
• test_join_condition_null_check_expression_template — ClickHouse isNotDistinctFrom() path
• test_join_condition_binary_operator_takes_precedence_over_expression — priority ordering

Manual validation: Took the exact SQL Tesseract generates for 2-fact and 4-fact multi-fact queries, replaced the OR (IS NULL AND IS NULL) join conditions with isNotDistinctFrom(), and verified all queries execute correctly against ClickHouse.

🤖 Generated with Claude Code