Loader speedup

[gkennos]

CLOSES: #9 , CLOSES #10

[Copilot]

Pull request overview

This PR improves loader observability and performance by adding phase-level timing logs around index/merge operations and introducing an insert_if_empty fast path (and automatic routing for replace/upsert when the target table is empty), addressing issues #9 and #10.

Changes:

• Added detailed, timed logging for index dropping, FK toggle, merge phases, and index rebuild steps.
• Implemented insert_if_empty merge strategy plus an empty-target probe that routes replace/upsert to the fast path.
• Added Postgres + e2e tests covering the new merge strategy and the new logging behavior; bumped version to 0.4.1 and updated changelog.

Reviewed changes

Copilot reviewed 6 out of 7 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
uv.lock	Updates lockfile artifacts and bumps project version reference to 0.4.1.
pyproject.toml	Bumps package version to 0.4.1.
CHANGELOG.md	Documents 0.4.1 changes (logging improvements and empty-table merge optimization).
src/orm_loader/tables/typing.py	Extends CSVTableProtocol with _target_has_rows() for typing support.
src/orm_loader/tables/loadable_table.py	Adds phase timing/logging, implements empty-target routing and insert_if_empty merge strategy.
tests/loaders/test_pg_loader.py	Adds Postgres tests for insert_if_empty behavior (success + error on non-empty).
tests/loaders/test_loader_e2e.py	Adds e2e tests for insert_if_empty, empty-target routing logs, and merge-phase logging.

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[Copilot]

Pull request overview

Copilot reviewed 6 out of 7 changed files in this pull request and generated 3 comments.

[Copilot]

Pull request overview

Copilot reviewed 6 out of 7 changed files in this pull request and generated 2 comments.

Comments suppressed due to low confidence (1)

tests/loaders/test_loader_e2e.py:615

• This assertion expects a "Merge operation SQL completed in ..." log message, but the current implementation only logs per-phase timings (delete/insert/upsert) and does not emit an overall SQL-completion message with that wording. Either adjust the test to match the existing logs, or add a total-merge-SQL timing log around merge_from_staging() to satisfy this expectation.

    assert any("Merge operation SQL completed in " in message for message in messages)
    assert any("Committing merged rows." in message for message in messages)