fix(cubesql): Push down UTCTIMESTAMP (CURRENT_TIMESTAMP)

[MazterQyou]

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

Description of Changes Made

This PR adds UTCTIMESTAMP SQL push down templates so CURRENT_TIMESTAMP can use SQL push down when needed. Related test is included.

[claude]

Claude finished @MazterQyou's task in 1m 20s —— View job

---

Code Review

LGTM — 0 blocking issues, 2 minor notes. Expand for details.

• Read PR diff
• Verify each driver's SQL is UTC-correct
• Check coverage vs. drivers without overrides
• Check Rust test wiring

Summary

Straightforward, well-scoped change: each dialect-specific sqlTemplates() gets a UTCTIMESTAMP entry, and a rewriter test in test_wrapper.rs verifies the push-down surfaces NOW() AT TIME ZONE 'UTC' inside a subquery filter. The Rust side already had BuiltinScalarFunction::UtcTimestamp wired via eval_utc_timestamp — this PR just supplies the missing template so the emitted SQL is dialect-appropriate.

Per-dialect correctness (spot check)

Driver	Template	Notes
Postgres / Redshift-parent	(NOW() AT TIME ZONE 'UTC')	✅ naive UTC timestamp
Redshift (override)	GETDATE()	✅ Redshift is UTC-internal; NOW() is leader-node only — override is well-reasoned
BigQuery	CURRENT_TIMESTAMP()	✅ always UTC
ClickHouse	now('UTC')	✅
MSSQL	GETUTCDATE()	✅
MySQL	UTC_TIMESTAMP()	✅
Oracle	SYS_EXTRACT_UTC(SYSTIMESTAMP)	✅
Snowflake	SYSDATE()	✅ TIMESTAMP_NTZ in UTC
Presto	CAST(NOW() AT TIME ZONE 'UTC' AS TIMESTAMP)	✅
Databricks	TO_UTC_TIMESTAMP(CURRENT_TIMESTAMP(), CURRENT_TIMEZONE())	✅
DuckDB	(NOW() AT TIME ZONE 'UTC')	✅ (requires ICU — commented)
Druid	CURRENT_TIMESTAMP	⚠️ correctness depends on sqlTimeZone=UTC — comment acknowledges
Pinot	NOW()	✅ epoch millis, inherently UTC

Minor notes (non-blocking)

1. Drivers with no override are unchanged. BaseQuery does not define functions.UTCTIMESTAMP, so dialects that only extend BaseQuery (Sqlite, Vertica, Hive, Crate, ElasticSearch, Firebolt, QuestDB, KSQL, Dremio, CubeStore) will not push down CURRENT_TIMESTAMP — they will fall back to non-pushed-down evaluation, which is safe. Worth mentioning in the PR body so it's clear this is scoped to the listed dialects. Trino/Athena inherit correctly through PrestodbQuery.

2. Druid sqlTimeZone assumption. If a downstream user overrides sqlTimeZone via query context, the pushed-down value will silently be wrong for that connection. The inline comment covers it, but if you want defense-in-depth you could emit TIMESTAMP_TO_MILLIS(CURRENT_TIMESTAMP) → MILLIS_TO_TIMESTAMP via UTC — probably not worth the complexity given the driver's default.

3. Test could be tightened. test_wrapper_filter_subquery_current_timestamp only asserts the substring "NOW() AT TIME ZONE 'UTC'" appears anywhere in the wrapped SQL. Consider also asserting the surrounding shape (e.g. that it lands inside the WHERE/subquery, not a leftover expression) so a regression that emits it in the wrong place would still fail. Not required.

Nothing else stands out — nice, focused patch.

• Branch: [`cubesql/utctimestamp-push-down`](https://github.com/cube-js/cube/tree/cubesql/utctimestamp-push-down)

[codecov]

Codecov Report

❌ Patch coverage is 96.87500% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 79.32%. Comparing base (fc0d82b) to head (66baf07).

Files with missing lines	Patch %	Lines
...t/cubesql/cubesql/src/compile/test/test_wrapper.rs	95.23%	1 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##           master   #11195   +/-   ##
=======================================
  Coverage   79.31%   79.32%           
=======================================
  Files         472      472           
  Lines       96921    96953   +32     
  Branches     3539     3539           
=======================================
+ Hits        76877    76908   +31     
- Misses      19538    19539    +1     
  Partials      506      506           

Flag	Coverage Δ
cube-backend	59.35% <100.00%> (+0.02%)	⬆️
cubesql	83.71% <95.45%> (+<0.01%)	⬆️

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[claude]

Claude finished @MazterQyou's task in 38s —— View job

---

Code Review

LGTM — 0 blocking issues, 3 minor notes. Expand for details.

• Read PR diff
• Verify each driver's SQL is UTC-correct
• Check coverage vs. drivers without overrides
• Check Rust test wiring

Summary

Focused, well-scoped change. Each dialect-specific sqlTemplates() gets a UTCTIMESTAMP entry so CURRENT_TIMESTAMP push-down emits dialect-appropriate SQL. BuiltinScalarFunction::UtcTimestamp was already wired in Rust via eval_utc_timestamp; this PR just supplies the missing templates. The new rewriter test in test_wrapper.rs verifies the push-down surfaces NOW() AT TIME ZONE 'UTC' inside a subquery filter, and a matching smoke test snapshot is added in smoke-cubesql.test.ts.

Per-dialect correctness

Driver	Template	Notes
Postgres	(NOW() AT TIME ZONE 'UTC')	✅ naive UTC timestamp
Redshift	GETDATE()	✅ Redshift is UTC-internal; NOW() is leader-node only — override well-reasoned
BigQuery	CURRENT_TIMESTAMP()	✅ always UTC
ClickHouse	now('UTC')	✅
MSSQL	GETUTCDATE()	✅
MySQL	UTC_TIMESTAMP()	✅
Oracle	SYS_EXTRACT_UTC(SYSTIMESTAMP)	✅
Snowflake	SYSDATE()	✅ TIMESTAMP_NTZ in UTC
Presto	CAST(NOW() AT TIME ZONE 'UTC' AS TIMESTAMP)	✅ (Trino/Athena inherit)
Databricks	TO_UTC_TIMESTAMP(CURRENT_TIMESTAMP(), CURRENT_TIMEZONE())	✅
DuckDB	(NOW() AT TIME ZONE 'UTC')	✅ (ICU bundled)
Druid	CURRENT_TIMESTAMP	⚠️ correctness depends on sqlTimeZone=UTC — comment acknowledges
Pinot	NOW()	✅ epoch millis, inherently UTC

Minor notes (non-blocking)

1. Drivers without overrides fall back to non-pushed-down evaluation. BaseQuery does not define functions.UTCTIMESTAMP, so dialects that only extend BaseQuery (Sqlite, Vertica, Hive, Crate, ElasticSearch, Firebolt, QuestDB, KSQL, Dremio, CubeStore) will not push down CURRENT_TIMESTAMP. That's safe — worth calling out in the PR body for clarity.

2. Druid sqlTimeZone assumption. If a connection overrides sqlTimeZone, the pushed-down value will silently be wrong. Inline comment covers it, but defense-in-depth (e.g. MILLIS_TO_TIMESTAMP(TIMESTAMP_TO_MILLIS(CURRENT_TIMESTAMP)) normalized to UTC) could remove the ambiguity — probably not worth the complexity.

3. Test could be tightened. test_wrapper_filter_subquery_current_timestamp only asserts the substring "NOW() AT TIME ZONE 'UTC'" appears anywhere in the wrapped SQL. Consider asserting the surrounding shape (that it lands inside the WHERE/subquery) so a regression emitting it in the wrong place still fails. Not required.

Nothing else stands out — nice, focused patch.

• Branch: cubesql/utctimestamp-push-down
•