Implement APD/IPD descriptor integration for parameter binding

[sfc-gh-makowalski]

Summary

• Replace parameter_bindings HashMap with proper ODBC APD/IPD descriptors as the source of truth for parameter binding. SQLBindParameter now writes to the APD (C type, data pointer, buffer length, indicator) and IPD (SQL type, column size, decimal digits, direction) separately.
• Add SQLNumParams and SQLDescribeParam — these read directly from the IPD descriptor, providing parameter metadata to applications.
• Add APD/IPD branches to SQLGetDescField/SQLSetDescField — applications can now bind parameters via descriptor manipulation as an alternative to SQLBindParameter.

Changes

File	Change
types.rs	New ApdDescriptor, ApdRecord, IpdDescriptor, IpdRecord structs; DescriptorRef now has Apd/Ipd variants; DescField gains ParameterType (1015) and Nullable (1008); Statement uses ApdDescriptor/IpdDescriptor instead of parameter_bindings HashMap
statement.rs	bind_parameter writes to APD+IPD; apply_parameter_bindings reads from APD+IPD; free_stmt(RESET_PARAMS) clears both descriptors; new num_params and describe_param functions
descriptor.rs	New get_apd_field/set_apd_field and get_ipd_field/set_ipd_field handlers
c_api.rs	New SQLNumParams and SQLDescribeParam FFI exports
param_binding.rs	odbc_bindings_to_json now takes &ApdDescriptor, &IpdDescriptor and reconstructs ParameterBinding at execution time
exports.def	Added SQLNumParams and SQLDescribeParam
handle_allocation.rs	Statement creation uses new descriptor types

Design

Per ODBC spec, parameter binding is split across two descriptors:

• APD (Application Parameter Descriptor): application-side buffer info (C data type, data pointer, buffer length, indicator/length pointer)
• IPD (Implementation Parameter Descriptor): server-side type info (SQL data type, column size, decimal digits, parameter direction, nullability)

SQLBindParameter populates both. At execution time, APD+IPD records are zipped into the existing ParameterBinding struct for the conversion pipeline (ParamConverter → ReadODBC → WriteJson → JSON). The conversion layer is unchanged.

Test plan

• All 540 existing unit tests pass
• Clippy clean, no warnings
• E2E bind parameter tests pass (CI)
• Verify SQLNumParams returns correct count after binding
• Verify SQLDescribeParam returns correct type info
• Verify SQLSetDescField on APD/IPD affects execution

Made with Cursor

[sfc-gh-makowalski]

Warning

This pull request is not mergeable via GitHub because a downstack PR is open. Once all requirements are satisfied, merge this PR as a stack on Graphite.
Learn more

• Implement APD/IPD descriptor integration for parameter binding #566 👈 (View in Graphite)
• Add ODBC-specific SQLBindParameter E2E tests #416
• Add TIME fetch support in conversion module #537
• Enable shared SQLBindParameter tests #415
• Refactor ODBC binding conversion into read/representation/write pipeline #399
• Remove Arrow bindings format #328
• main

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