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FIX: FetchMany(number of rows) ignores batch size with LOB columns #346

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FIX: FetchMany(number of rows) ignores batch size with LOB columns #346

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c403899
Fix for FetchMany(number of rows) ignores batch size when table conta…
dlevy-msft-sql Nov 25, 2025
f96d14c
First round of code review fixes
dlevy-msft-sql Nov 25, 2025
e135e40
Fix test_fetchone
dlevy-msft-sql Nov 25, 2025
b5dbe34
Suggested changes from code review
dlevy-msft-sql Dec 9, 2025
5792612
Merge branch 'main' into Fix-fetchmany(num_rows)
dlevy-msft-sql Dec 10, 2025
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10 changes: 6 additions & 4 deletions mssql_python/pybind/ddbc_bindings.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -4012,13 +4012,15 @@ SQLRETURN FetchMany_wrap(SqlHandlePtr StatementHandle, py::list& rows, int fetch
lobColumns.push_back(i + 1); // 1-based
}
}


// Initialized to 0 for LOB path counter; overwritten by ODBC in non-LOB path;
SQLULEN numRowsFetched = 0;
// If we have LOBs → fall back to row-by-row fetch + SQLGetData_wrap
if (!lobColumns.empty()) {
LOG("FetchMany_wrap: LOB columns detected (%zu columns), using per-row "
"SQLGetData path",
lobColumns.size());
while (true) {
while (numRowsFetched < (SQLULEN)fetchSize) {
ret = SQLFetch_ptr(hStmt);
if (ret == SQL_NO_DATA)
break;
Expand All @@ -4029,6 +4031,7 @@ SQLRETURN FetchMany_wrap(SqlHandlePtr StatementHandle, py::list& rows, int fetch
SQLGetData_wrap(StatementHandle, numCols, row, charEncoding,
wcharEncoding); // <-- streams LOBs correctly
rows.append(row);
numRowsFetched++;
}
return SQL_SUCCESS;
}
Expand All @@ -4042,8 +4045,7 @@ SQLRETURN FetchMany_wrap(SqlHandlePtr StatementHandle, py::list& rows, int fetch
LOG("FetchMany_wrap: Error when binding columns - SQLRETURN=%d", ret);
return ret;
}

SQLULEN numRowsFetched;

SQLSetStmtAttr_ptr(hStmt, SQL_ATTR_ROW_ARRAY_SIZE, (SQLPOINTER)(intptr_t)fetchSize, 0);
SQLSetStmtAttr_ptr(hStmt, SQL_ATTR_ROWS_FETCHED_PTR, &numRowsFetched, 0);

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