[*] fix error hint in timetable.cron_split_to_arrays

[pashagolub]

Summary

timetable.cron_split_to_arrays joined its RAISE EXCEPTION hint with + instead of ||. PostgreSQL has no unique text + text operator, so an unrecognised cron field raised the wrong error.

 RAISE EXCEPTION 'Value ("%") not recognized', a_element[i_index]
-    USING HINT = 'fields separated by space or tab.'+
-       'Values allowed: numbers (value list with ","), '+
+    USING HINT = 'fields separated by space or tab. ' ||
+        'Values allowed: numbers (value list with ","), ' ||
         'any value with "*", range of value with "-" and step values with "/"!';

 internal/pgengine/
 ├── sql/cron.sql                # fresh installs
+├── sql/migrations/00850.sql    # existing installs, CREATE OR REPLACE FUNCTION
 ├── sql/init.sql                # records 00850 in timetable.migration
 └── migration.go                # registers 00850
 cmd/pg_timetable/main.go        # dbapi 00820 → 00850

Found by the pgcov SQL tests in #850, which is stacked on this PR.

Evidence

assertCronSplitRejectsValue runs SELECT timetable.cron_split_to_arrays('foo * * * *'). Two tests call it: TestCronSplitToArraysUnknownValue on a fresh install, and TestMigrations after migrating from 00000.sql.

• Before: --- FAIL: TestCronSplitToArraysUnknownValue

  Error: Not equal: expected: "P0001"
  Error: Not equal: expected: "Value (\"foo\") not recognized"
  Error: "Could not choose a best candidate operator. You might need to add explicit type casts."
         does not contain "fields separated by space or tab. Values allowed"
  

  After: both tests pass.

Merge Danger

Door: one-way

Migration 00850 runs on existing installs and is recorded in timetable.migration. It only replaces one function body, so a later migration can change it again.

Blast Radius: small

Only the error path for an unrecognised cron field changes, and that path already failed with the wrong error. Valid cron strings take the same code path as before.

[coveralls]

Coverage Report for CI Build 37968493685

Coverage decreased (-0.07%) to 87.49%

Details

• Coverage decreased (-0.07%) from the base build.
• Patch coverage: 2 of 2 lines across 1 file are fully covered (100%).
• 8 coverage regressions across 3 files.

Uncovered Changes

No uncovered changes found.

Coverage Regressions

8 previously-covered lines in 3 files lost coverage.

File	Lines Losing Coverage	Coverage
internal/pgengine/log_hook.go	4	78.89%
cmd/pg_timetable/service_windows.go	2	74.88%
internal/otel/otel.go	2	90.98%

---

Coverage Stats

Relevant Lines:	2446
Covered Lines:	2140
Line Coverage:	87.49%
Coverage Strength:	0.89 hits per line

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💛 - Coveralls

[postgresql007]

looks good