feat(postgres): add copyfrom support

[kellen-miller]

Closes#63

[Copilot]

Pull request overview

This PR implements support for the :copyfrom command in sqlc-gen-python, enabling efficient bulk insert operations. The implementation leverages SQLAlchemy's executemany behavior by passing lists of parameter dictionaries to Connection.execute().

Key Changes:

• Added :copyfrom command support with automatic handling of both struct and non-struct parameters
• Removed the previous error that blocked CopyFrom usage
• Added comprehensive test coverage and examples demonstrating both sync and async usage

Reviewed changes

Copilot reviewed 44 out of 45 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
internal/gen.go	Core implementation: adds BuildCopyFromBody, addCopyFromArgs, and buildStructToDictList methods; removes CopyFrom error; adds switch cases for :copyfrom in sync/async queriers
internal/imports.go	Adds import logic for typing.List and typing.Any types needed by copyfrom methods
internal/endtoend/testdata/copyfrom/*	New end-to-end test case with schema, queries, and expected generated code covering multiple copyfrom scenarios
examples/src/authors/query.sql	Adds example CreateAuthorsBatch copyfrom query
examples/src/authors/query.py	Generated code demonstrating copyfrom method with List[Any] parameter
examples/src/tests/test_authors.py	Test cases validating both sync and async copyfrom functionality
README.md	Documentation explaining copyfrom usage with examples for both List[Any] and typed struct parameters
internal/endtoend/testdata/*/sqlc.yaml	Updated sha256 hashes for new WASM binary version
internal/endtoend/testdata//python/.py	Updated generated file version comments from v1.28.0 to v1.29.0
.gitignore	Adds .idea/ IDE directory to gitignore

---

💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.

[Copilot]

Using list() to create an empty list is less efficient than using a list literal []. In Python, [] is more idiomatic and has better performance since it doesn't require a function call. Consider updating the code generation to use [] instead of list().

[kellen-miller]

I’m not sure if the custom AST/printer that generates the python supports [] without adding a new node/printing logic. It currently emits list() for empty lists so I’ve left list() for now. Happy to change if the generator can do literals though.

[devstein]

Hey @kellen-miller - will try take a look at this soon. Feel free to ping me if you don't get a review in the next week or so!

[kellen-miller]

Hey @devstein have you had a chance to review this pr?