[Enhancement] Enable zone-map pruning for date_trunc predicates

[zhangyaqi1989]

Why I'm doing:

Predicates such as date_trunc('day', ts) = '2026-09-10' reach the scan as expression predicates, but DATE_TRUNC is missing from the FE's monotonic-function allowlist. The BE therefore cannot use the expression for zone-map pruning.

What I'm doing:

Add DATE_TRUNC to the existing allowlist. Its unit is already required to be a constant by function analysis, and truncation preserves timestamp ordering. The existing recursive check still rejects non-monotonic child expressions; the BE already handles equality by deriving >= and <= zone-map predicates.

Add a serialization regression test covering DATE/DATETIME units, nullable and non-nullable columns, equality and range predicates, and a non-monotonic CASE input.

Related issue: none.

Validation

• Confirmed the new regression fails on unmodified upstream: DATE: day ==> expected: <true> but was: <false>.

• With the fix, ExprToThriftTest passes: 2 tests, 0 failures/errors. Run in a Linux ARM64 container with JDK 17:

  cd fe
  FE_UT_PARALLEL=1 PYTHON=python3 mvn -B -ntp -pl fe-core -am \
    -Dtest=ExprToThriftTest -Dsurefire.failIfNoSpecifiedTests=false \
    -DfailIfNoTests=false -Djacoco.skip=true -Dmaven.clean.skip=true test

• Checked truncation ordering with synthetic NULL, minimum/maximum date, leap-day, and subsecond inputs on a local StarRocks instance. These are boundary sanity checks; the regression above verifies the changed upstream serialization path.

• mvn -B -ntp -pl fe-core checkstyle:check: passed with 0 violations.

Reproducer

CREATE TABLE date_trunc_pruning (ts DATETIME NOT NULL)
DUPLICATE KEY(ts)
DISTRIBUTED BY HASH(ts) BUCKETS 1
PROPERTIES ('replication_num' = '1');

INSERT INTO date_trunc_pruning
SELECT minutes_add('2025-01-01 00:00:00', generate_series)
FROM TABLE(generate_series(0, 999999));

SET enable_query_cache = false;
EXPLAIN ANALYZE
SELECT count(*) FROM date_trunc_pruning
WHERE date_trunc('day', ts) = '2026-09-10';

DROP TABLE date_trunc_pruning;

Observability: reviewed the existing RawRowsRead, ReadPagesNum, and ZoneMapIndexFilterRows scan-profile counters. They already expose the pruning improvement and remain unchanged; no new metrics are needed.

What type of PR is this:

• BugFix
• Feature
• Enhancement
• Refactor
• UT
• Doc
• Tool

Does this PR entail a change in behavior?

• Yes, this PR will result in a change in behavior.
• No, this PR will not result in a change in behavior.

If yes, please specify the type of change:

• Interface/UI changes: syntax, type conversion, expression evaluation, display information
• Parameter changes: default values, similar parameters but with different default values
• Policy changes: use new policy to replace old one, functionality automatically enabled
• Feature removed
• Miscellaneous: upgrade & downgrade compatibility, etc.

Eligible DATE_TRUNC predicates can prune additional pages. SQL results and configuration interfaces are unchanged.

Checklist:

• I have added test cases for my bug fix or my new feature
• This pr needs user documentation (for new or modified features or behaviors)
  • I have added documentation for my new feature or new function
  • This pr needs auto generate documentation
• This is a backport pr

Bugfix cherry-pick branch check:

• I have checked the version labels which the pr will be auto-backported to the target branch
  • 4.1
  • 4.0
  • 3.5

[CelerData-Reviewer]

@codex review

[chatgpt-codex-connector]

Codex Review: Didn't find any major issues. More of your lovely PRs please.

Reviewed commit: 9ec179629d

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[chatgpt-codex-connector]

Codex Review Summary

This comment shows the latest Codex review activity on this pull request.

Review	Status	Commit	Review trigger
📝 Code Review	✅ Completed 2026-09-11T22:56:49.180704Z	9ec1796	Manual request

ℹ️ About Codex in GitHub

Your team has set up Codex to review pull requests in this repo. Reviews are triggered when you

• Open a pull request for review
• Mark a draft as ready
• Comment "@codex review" or "@codex security review".

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[github-actions]

[BE Incremental Coverage Report]

✅ pass : 0 / 0 (0%)

[github-actions]

[Java-Extensions Incremental Coverage Report]

✅ pass : 0 / 0 (0%)

[github-actions]

[FE Incremental Coverage Report]

✅ pass : 1 / 1 (100.00%)

file detail

	path	covered_line	new_line	coverage	not_covered_line_detail
🔵	com/starrocks/sql/ast/expression/FunctionCallExpr.java	1	1	100.00%	[]

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud