Report -1 for statements that are not INSERT, UPDATE or DELETE

[alaricd]

Two affected-row counts disagreed with the ADO.NET contract:\n\n- ExecuteNonQuery now returns -1 for non-row-counting statements and counts INSERT, UPDATE, DELETE, COPY, and MERGE.\n- ExecuteReader().RecordsAffected counts those statements as well.\n- DML statements with RETURNING use the query result row count, including materialized and streaming results.\n\nTests cover non-DML, zero-row DML, MERGE, COPY, DML with RETURNING, and RecordsAffected through ExecuteReader. The focused ExecuteNonQueryTests suite passes 11/11.\n\nFound by the pengdows ADO.NET conformance suite, which runs the documented System.Data.Common contract against every provider.

[coveralls]

Coverage Report for CI Build 39438113753

Coverage increased (+0.1%) to 92.624%

Details

• Coverage increased (+0.1%) from the base build.
• Patch coverage: 11 of 11 lines across 2 files are fully covered (100%).
• No coverage regressions found.

Uncovered Changes

No uncovered changes found.

Coverage Regressions

No coverage regressions found.

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Coverage Stats

Relevant Lines:	4026
Covered Lines:	3791
Line Coverage:	94.16%
Relevant Branches:	2305
Covered Branches:	2073
Branch Coverage:	89.93%
Branches in Coverage %:	Yes
Coverage Strength:	1001240.48 hits per line

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💛 - Coveralls

[Giorgi]

Thanks. For INSERT, UPDATE, DELETE, SELECT, DDL and SET this matches Npgsql, but I found two problems. I ran the same statements against this branch, against develop, and with Npgsql 10.0.0 against PostgreSQL 18.3 (ExecuteNonQuery, and ExecuteReader → read everything → Close → RecordsAffected; DuckDB with UseStreamingMode both off and on, with the same results):

Statement	develop (ExecuteNonQuery / RecordsAffected)	this PR	Npgsql
MERGE (1 update + 1 insert)	2 / -1	-1 / -1	2 / 2
COPY t FROM 'file.csv' (2 rows)	2 / -1	-1 / -1	2 / 2
COPY t TO 'file.csv' (3 rows)	3 / -1	-1 / -1	not tested
INSERT … RETURNING (2 rows)	0 / -1	0 / 0	2 / 2
UPDATE … RETURNING (3 rows)	0 / -1	0 / 0	3 / 3

1. MERGE and COPY now return -1

On develop, ExecuteNonQuery returns their row count. CountsRows accepts only Insert, Update and Delete, so both are now reported as -1.

MERGE also needs the bindings. DuckDB 1.5.6 returns DUCKDB_STATEMENT_TYPE_MERGE_INTO = 30 from duckdb_result_statement_type (see duckdb.h), but DuckDBStatementType stops at Multi = 27, so a MERGE arrives as an undefined value. Could you:

• add CopyDatabase = 28, UpdateExtensions = 29 and MergeInto = 30 to DuckDBStatementType;
• count MergeInto and Copy in CountsRows;
• add tests for MERGE and COPY?

2. RETURNING reports 0

duckdb_rows_changed returns 0 for any result whose return type isn't CHANGED_ROWS (src/main/capi/result-c.cpp), and a statement with RETURNING produces a query result. So INSERT … RETURNING and UPDATE … RETURNING report 0, which by the contract means "no rows were affected". That is the optimistic-concurrency misreading the description mentions. It's not a regression (develop returns 0 from ExecuteNonQuery too), but the description gives RETURNING as a reason for the change. Could you either handle it, for example by counting the rows of the result for an INSERT, UPDATE or DELETE that returns a query result, or take RETURNING out of the description, so that it doesn't look covered?

Nit: ExecuteNonQueryTests.cs ends with an extra blank line after the closing }.

[alaricd]

Addressed the review feedback in 5327966:\n\n- Added the DuckDB 1.5.6 statement types CopyDatabase = 28, UpdateExtensions = 29, and MergeInto = 30 (and aligned the enum with the C API).\n- COPY and MERGE are now included in affected-row counting.\n- Query-result row counts are used for DML with RETURNING, so both ExecuteNonQuery and ExecuteReader().RecordsAffected report the returned row count in materialized and streaming modes.\n- Added focused MERGE, COPY, and RETURNING tests; the focused ExecuteNonQueryTests suite passes 11/11.\n- Removed the extra trailing blank line from ExecuteNonQueryTests.cs.\n\nThe behavior is still grounded in the pengdows ADO.NET conformance suite.