fix(connectors): unify extract_column_value into single free function

[atharvalade]

Which issue does this PR close?

Closes #3172

Rationale

Bug fixes or new type support added to one copy of extract_column_value silently won't apply to the other, causing divergence between sequential and parallel code paths.

What changed?

The Postgres source connector had extract_column_value as a method on PostgresSource (&self), making it impossible to call from static/parallel contexts without duplicating the function. Any future parallel/chunked path would need its own copy.

Converted it to a single free function callable from any context. Added missing DATE (via chrono::NaiveDate) and BPCHAR type handling that the parallel copy on the benchmark branch had but this version lacked.

Local Execution

• Passed
• Pre-commit hooks ran

AI Usage

1. Opus 4.6
2. exploration and implementation guidance
3. Verified via cargo check, clippy -D warnings, fmt --check, all 19 unit tests passing, CI lint scripts passing
4. Yes, all code can be explained

[codecov]

Codecov Report

❌ Patch coverage is 0% with 101 lines in your changes missing coverage. Please review.
✅ Project coverage is 18.33%. Comparing base (2337883) to head (d8fc00e).
⚠️ Report is 3 commits behind head on master.

Files with missing lines	Patch %	Lines
core/connectors/sources/postgres_source/src/lib.rs	0.00%	101 Missing ⚠️

❌ Your patch check has failed because the patch coverage (0.00%) is below the target coverage (50.00%). You can increase the patch coverage or adjust the target coverage.

Additional details and impacted files

@@              Coverage Diff              @@
##             master    #3199       +/-   ##
=============================================
- Coverage     74.18%   18.33%   -55.86%     
  Complexity      943      943               
=============================================
  Files          1200     1198        -2     
  Lines        109645    94898    -14747     
  Branches      86534    71804    -14730     
=============================================
- Hits          81345    17396    -63949     
- Misses        25553    77084    +51531     
+ Partials       2747      418     -2329     

Components	Coverage Δ
Rust Core	0.89% <0.00%> (-74.54%)	⬇️
Java SDK	58.44% <ø> (ø)
C# SDK	69.13% <ø> (-0.31%)	⬇️
Python SDK	81.43% <ø> (ø)
Node SDK	91.44% <ø> (ø)
Go SDK	39.91% <ø> (ø)

Files with missing lines	Coverage Δ
core/connectors/sources/postgres_source/src/lib.rs	40.82% <0.00%> (-27.08%)	⬇️

... and 685 files with indirect coverage changes

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[lukaszzborek]

@atharvalade
In issue is Postgres source connector has two nearly identical functions and to remove one. But i don't see second one.
I'm jus asking for clarification, if i don't see something

Also remeber about #3196 where you also add Date

[github-actions]

This pull request has been automatically marked as stale because it has not had recent activity. It will be closed in 7 days if no further activity occurs.

If you need a review, please ensure CI is green and the PR is rebased on the latest master. Don't hesitate to ping the maintainers - either @core on Discord or by mentioning them directly here on the PR.

Thank you for your contribution!

[hubcio]

/author

[github-actions]

This pull request has been automatically marked as stale because it has not had recent activity. It will be closed in 7 days if no further activity occurs.

If you need a review, please ensure CI is green and the PR is rebased on the latest master. Don't hesitate to ping the maintainers - either @core on Discord or by mentioning them directly here on the PR.

Thank you for your contribution!

[atharvalade]

@atharvalade In issue is Postgres source connector has two nearly identical functions and to remove one. But i don't see second one. I'm jus asking for clarification, if i don't see something

Also remeber about #3196 where you also add Date

Good catch, the second copy (extract_column_value_static) lives on the feat/pg-to-iceberg-benchmark branch (not yet merged to master), where the parallel/chunked polling paths were added. This PR preemptively converts the method to a free function so that when those paths land, they can call the same function instead of duplicating it. I'll drop the DATE addition here since #3196 already covers it, and rebase on latest master.

[atharvalade]

/ready

[hubcio]

no reason to include these changes in this PR.

[hubcio]

BPCHAR is the only new behavior in this PR but nothing exercises it. codecov flags 0% patch coverage (101 missing lines). a single round-trip test reading a char(n) column closes the gap and prevents the same divergence the issue is trying to prevent.

if possible, just make it part of some existing tests instead of making a new tc.