GetOrdinal: case-insensitive fallback and IndexOutOfRangeException

[alaricd]

DuckDBDataReader.GetOrdinal only finds an exact, case-sensitive match. For a name that isn't found it throws DuckDBException.

The contract

IDataRecord.GetOrdinal, Remarks:

GetOrdinal performs a case-sensitive lookup first. If it fails, a second case-insensitive search is made. GetOrdinal is kana-width insensitive. If the index of the named field is not found, an IndexOutOfRangeException is thrown.

Why it matters

DuckDB folds unquoted identifiers, so SELECT id FROM t and reader.GetOrdinal("Id") refer to the same column, yet the second call throws. Mappers (Dapper, hand-written reader["Name"] code) that work against SqlClient, Npgsql, MySqlConnector and Microsoft.Data.Sqlite fail on DuckDB because of how a property happens to be capitalised. Code that catches IndexOutOfRangeException to test for an optional column, as the contract allows, gets a DuckDBException instead.

Change

• The exact match from columnMapping is still tried first, so a column whose name matches exactly always wins (SELECT 1 AS Id, 2 AS id keeps returning 0 for "Id" and 1 for "id").
• If that fails, the reader compares names with CompareOptions.IgnoreCase | IgnoreKanaType | IgnoreWidth, which is what "case-insensitive … kana-width insensitive" describes.
• An unknown name throws IndexOutOfRangeException.

Behaviour change: callers that catch DuckDBException from GetOrdinal need to catch IndexOutOfRangeException. The two tests that pinned the old type (GetOrdinalReturnsColumnIndex, GetOrdinalRepeatedColumnReturnsFirstIndex) now expect the documented one.

New tests: GetOrdinalFallsBackToACaseInsensitiveMatch (exact match wins, case and width folding) and GetOrdinalThrowsIndexOutOfRangeForAnUnknownName. The full suite passes.

Conformance tests: GetOrdinal_works, GetOrdinal_throws_when_out_of_range.

Found by the pengdows ADO.NET conformance suite, which runs the documented System.Data.Common contract against every provider; each failure it reports cites the learn.microsoft.com sentence the provider departs from.

🤖 Generated with Claude Code

[coveralls]

Coverage Report for CI Build 39416608021

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Coverage increased (+0.07%) to 92.561%

Details

• Coverage increased (+0.07%) from the base build.
• Patch coverage: 5 of 5 lines across 1 file are fully covered (100%).
• No coverage regressions found.

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Coverage Stats

Relevant Lines:	4016
Covered Lines:	3780
Line Coverage:	94.12%
Relevant Branches:	2289
Covered Branches:	2056
Branch Coverage:	89.82%
Branches in Coverage %:	Yes
Coverage Strength:	1003742.96 hits per line

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