fix(connectors): defer postgres source progress until ack

[rohankumardubey]

Which issue does this PR address?

Closes #3635

Rationale

The PostgreSQL source advanced tracking offsets, deleted or marked rows, and consumed CDC changes before Iggy confirmed delivery. A failed send could therefore permanently skip source records.

What changed?

PostgreSQL polling now stages cursor updates and row operations until the runtime reports a successful batch acknowledgment. NACK discards the staged work, while ACK commits the state and performs the pending delete or mark operations.

CDC now peeks logical-slot changes and advances the slot only after acknowledgment. A deterministic regression test stops Iggy during delivery and verifies that the PostgreSQL rows are redelivered after restart.

Local Execution

• Passed cargo fmt --all -- --check
• Passed cargo clippy -p iggy_connector_postgres_source -p integration --all-features --all-targets -- -D warnings
• Passed all 70 PostgreSQL source unit tests
• Passed all 7 PostgreSQL polling integration tests
• Passed both PostgreSQL CDC integration tests
• Passed the deterministic kill-server regression test
• Passed git diff --check

[github-actions]

Thanks for the PR. It is labeled S-waiting-on-review and queued for review.

Slash commands (own line, regular comment) move it around the queue:

• /ready - back to S-waiting-on-review after addressing feedback
• /author - flip to S-waiting-on-author while you finish changes
• /request-review @user-or-team - request a reviewer

See CONTRIBUTING.md for details.

[codecov]

Codecov Report

❌ Patch coverage is 88.03596% with 173 lines in your changes missing coverage. Please review.
✅ Project coverage is 67.79%. Comparing base (1b4ebee) to head (36a5494).

Files with missing lines	Patch %	Lines
core/connectors/sources/postgres_source/src/lib.rs	88.18%	96 Missing and 45 partials ⚠️
core/connectors/runtime/src/source.rs	79.54%	13 Missing and 5 partials ⚠️
core/connectors/sdk/src/source.rs	88.49%	13 Missing ⚠️
core/connectors/runtime/src/manager/source.rs	96.15%	1 Missing ⚠️

Additional details and impacted files

@@              Coverage Diff              @@
##             master    #3957       +/-   ##
=============================================
- Coverage     87.13%   67.79%   -19.34%     
  Complexity     1455     1455               
=============================================
  Files          1273     1272        -1     
  Lines        215297   178678    -36619     
  Branches     179911   143293    -36618     
=============================================
- Hits         187593   121140    -66453     
- Misses        23178    52922    +29744     
- Partials       4526     4616       +90     

Components	Coverage Δ
Rust Core	64.08% <88.03%> (-24.08%)	⬇️
Java SDK	67.58% <ø> (ø)
C# SDK	77.15% <ø> (+0.03%)	⬆️
Python SDK	90.97% <ø> (ø)
PHP SDK	85.67% <ø> (ø)
Node SDK	94.53% <ø> (-1.74%)	⬇️
Go SDK	69.48% <ø> (+0.03%)	⬆️

Files with missing lines	Coverage Δ
core/connectors/runtime/src/stream.rs	91.15% <100.00%> (+1.05%)	⬆️
core/connectors/runtime/src/manager/source.rs	93.15% <96.15%> (+0.15%)	⬆️
core/connectors/sdk/src/source.rs	90.34% <88.49%> (-0.36%)	⬇️
core/connectors/runtime/src/source.rs	86.51% <79.54%> (+0.41%)	⬆️
core/connectors/sources/postgres_source/src/lib.rs	79.45% <88.18%> (+6.14%)	⬆️

... and 404 files with indirect coverage changes

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[rohankumardubey]

/ready

[rohankumardubey]

/request-review @hubcio

[hubcio]

a few things without diff lines to hang them on:

• .claude/skills/connector-source/SKILL.md still teaches the pre-ack pattern this pr removes (the "matches poll_tables" snippet writes cursors during poll, "always return state in every ProducedMessages" no longer holds for empty polls, and state-serialization failure is now a hard poll error, lib.rs:288-296) and doesn't mention on_batch_result at all - needs an update to the new contract.
• mark_or_delete_processed_rows maps db errors to Error::InvalidRecord (lib.rs:732, :751) - misleading now that these errors surface through the ack path; Error::Connection like advance_replication_slot uses would fit better.
• README.md:15 still promises offset tracking "avoid duplicates" - at-least-once redelivery means duplicates are possible; and README.md:57 documents the poll_interval default as 1s while the code fallback is 10s (lib.rs:180).

[hubcio]

@rohankumardubey please write
/ready
when PR is ready for review. at any top level comment, in the beginning of any line. this will let know maintainers that something is ready for review by flipping gh labels.

[rohankumardubey]

/ready

[hubcio]

looks like CI is failing.

[rohankumardubey]

The failure came from a merge-resolution type mismatch in the TLS connection-string branch. Thanks @hubcio

[rohankumardubey]

/ready

[rohankumardubey]

/ready