[vistart]

Description

Implements the backend half of the portable seconds_between expression added in
rhosocial/python-activerecord#129: format_seconds_between_expression() renders
end - start in signed, fractional seconds. Subtracting two PostgreSQL timestamps yields an interval, so the formatter wraps the difference in EXTRACT(EPOCH FROM (end - start)), which already carries the sign and the microseconds.

The core raises UnsupportedFeatureError until a dialect adapts the hook, so this
change is what makes the expression usable on this engine. The implementation lives in
src/rhosocial/activerecord/backend/impl/postgres/mixins/datetime.py.

Type of change

• feat: A new feature
• docs: Documentation for the new capability
• test: Tests for the new capability
• chore: CI installs the core from the feature branch (see below)
• perf / ci / build / revert: not applicable

Breaking Change

• Yes, for end-users (backward-incompatible API changes)
• Yes, for backend developers (internal architectural changes that may affect custom implementations)
• No breaking changes

Impact on End-Users:
No backward-incompatible changes are expected: the expression is new, and nothing
existing changes shape.

Impact on Backend Developers (Custom Implementations):
None. The dialect hook is additive; implementations that do not override it keep
inheriting the core refusal.

Related Repositories/Packages

Requires rhosocial/python-activerecord#129 (branch feature/extract-epoch).

.github/workflows/test.yml now installs the core from feature/extract-epoch
instead of release/v1.0.0.dev30, so CI exercises the core change and this backend
together (see the chore(ci) commit on this branch). That pin is temporary: it should
go back to the release branch once the core PR merges.

Testing

• I have added new tests to cover my changes.
• I have updated existing tests to reflect my changes.
• All existing tests pass.
• This change has been tested on the target engine.

Test Plan:

• tests/rhosocial/activerecord_postgres_test/feature/backend/postgres/test_postgres_seconds_between.py

Checklist

• My code follows the project's code style guidelines.
• I have performed a self-review of my own code.
• I have commented my code, particularly in hard-to-understand areas.
• I have made corresponding changes to the documentation (Docstrings, README.md, etc.).
• My changes generate no new warnings.
• I have added a Changelog fragment (added in a follow-up commit, once the PR number is known).
• I have verified that my changes do not introduce SQL injection vulnerabilities.
• I have checked for potential performance regressions.

Additional Notes

The changelog fragment is intentionally deferred until the PR number exists; it is
added as changelog.d/<pr_number>.added.md right after the PR opens.

[codecov]

Codecov Report

❌ Patch coverage is 83.33333% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 77.90%. Comparing base (28b001e) to head (11025a7).

Files with missing lines	Patch %	Lines
...iverecord/backend/impl/postgres/mixins/datetime.py	83.33%	1 Missing ⚠️

Additional details and impacted files

@@                  Coverage Diff                  @@
##           release/v1.0.0.dev17      #65   +/-   ##
=====================================================
  Coverage                 77.90%   77.90%           
=====================================================
  Files                       355      355           
  Lines                     17504    17509    +5     
  Branches                   2805     2805           
=====================================================
+ Hits                      13636    13641    +5     
  Misses                     2870     2870           
  Partials                    998      998           

Flag	Coverage Δ
postgres-18	77.90% <83.33%> (+<0.01%)	⬆️
python-3.14	77.90% <83.33%> (+<0.01%)	⬆️
unittests	77.90% <83.33%> (+<0.01%)	⬆️

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[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