Address review comments

Author: HyukjinKwon

cpp/src/arrow/flight/sql/odbc/odbc_impl/odbc_statement.cc

@@ -25,6 +25,7 @@
 #include "arrow/flight/sql/odbc/odbc_impl/spi/result_set_metadata.h"
 #include "arrow/flight/sql/odbc/odbc_impl/spi/statement.h"
 #include "arrow/flight/sql/odbc/odbc_impl/types.h"
+#include "arrow/type.h"
 
 #include <sql.h>
 #include <sqlext.h>
@@ -746,8 +747,8 @@ SQLRETURN ODBCStatement::GetData(SQLSMALLINT record_number, SQLSMALLINT c_type,
   // Get precision and scale from IRD (implementation row descriptor) as defaults.
   // These can be overridden by ARD (application row descriptor) if specified.
   const DescriptorRecord& ird_record = ird_->GetRecords()[record_number - 1];
-  int precision = ird_record.precision > 0 ? ird_record.precision
-                                           : 38;  // Default to max decimal precision
+  int precision =
+      ird_record.precision > 0 ? ird_record.precision : Decimal128Type::kMaxPrecision;
   int scale = ird_record.scale;
 
   if (c_type == SQL_ARD_TYPE) {

cpp/src/arrow/flight/sql/odbc/tests/statement_test.cc

@@ -646,7 +646,8 @@ TEST_F(StatementRemoteTest, TestSQLExecDirectVarbinaryQueryDefaultType) {
   EXPECT_EQ('\xEF', varbinary_val[2]);
 }
 
-TYPED_TEST(StatementTest, TestGetDataPrecisionScaleUsesIRDAsDefault) {
+// TODO(GH-48730): Enable this test when ARD/IRD descriptor support is fully implemented
+TYPED_TEST(StatementTest, DISABLED_TestGetDataPrecisionScaleUsesIRDAsDefault) {
   // Verify that SQLGetData uses IRD precision/scale as defaults when ARD values are unset
   std::wstring wsql = L"SELECT CAST('123.45' AS NUMERIC) as decimal_col;";
   std::vector<SQLWCHAR> sql(wsql.begin(), wsql.end());
@@ -692,7 +693,8 @@ TYPED_TEST(StatementTest, TestGetDataPrecisionScaleUsesIRDAsDefault) {
   EXPECT_EQ(static_cast<SQLSMALLINT>(ird_scale), numeric_val.scale);
 }
 
-TYPED_TEST(StatementTest, TestGetDataPrecisionScaleUsesARDWhenSet) {
+// TODO(GH-48730): Enable this test when ARD/IRD descriptor support is fully implemented
+TYPED_TEST(StatementTest, DISABLED_TestGetDataPrecisionScaleUsesARDWhenSet) {
   // Verify that SQLGetData uses ARD precision/scale when set, for both SQL_ARD_TYPE and
   // SQL_C_DEFAULT
   std::wstring wsql = L"SELECT CAST('123.45' AS NUMERIC) as decimal_col;";