GH-745: bind money-range Decimal batches as SQL_NUMERIC in executemany

Author: IMGillusion

CHANGELOG.md

@@ -85,7 +85,18 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
   `money`/`varchar` in data-type precedence, `WHERE money_or_varchar_col = ?` can
   add a `CONVERT_IMPLICIT` on the column side that turns an index seek into a scan.
   `executemany` intentionally keeps its batch `VARCHAR` string binding (GH-503);
-  the remaining money-range case there is tracked in #745.
+  the remaining money-range case there is tracked in #745 (fixed below).
+- **GH-745:** A `Decimal` batch in the MONEY / SMALLMONEY range passed to
+  `executemany()` is now re-declared as `SQL_NUMERIC` (with the batch-wide maximum
+  scale) instead of keeping the sample row's `VARCHAR` money shortcut, mirroring
+  the GH-740 fix on the `execute()` paths. Previously such a batch compared
+  against a smaller `numeric`/`decimal` column (`WHERE v = ?`) made SQL Server
+  convert each row's `varchar`→`numeric` and raise an arithmetic overflow. The
+  batch still string-binds (GH-503), and `decimalDigits` uses the max scale across
+  the whole batch so mixed-scale rows all fit the declared type (a sample-only
+  switch would regress the GH-557 mixed-sign sizing). Only pure-Decimal columns
+  fully inside the money range are affected; wider values, mixed-type columns, and
+  `setinputsizes()`-typed columns are untouched.
 - **GH-725:** The `timeout` parameter of `connect()` / `Connection(...)` now
   correctly sets the **login (connection-attempt) timeout**
   (`SQL_ATTR_LOGIN_TIMEOUT`), matching pyodbc and its own docstring. Previously

mssql_python/cursor.py

@@ -2371,6 +2371,38 @@ def _compute_column_type(self, column):
 
         return sample_value, None, None, max_decimal_formatted_len
 
+    def _apply_money_batch_declared_type(self, paraminfo, column):
+        """GH-745: re-declare a money-range Decimal column as SQL_NUMERIC.
+
+        The auto-detection sample path takes the VARCHAR money shortcut
+        (see _map_sql_type), but a money-range Decimal compared against a
+        smaller numeric column overflows on the server side when bound as
+        VARCHAR - the same bug GH-740 fixed on the execute() paths. Declare
+        SQL_NUMERIC instead; the existing override below keeps the
+        SQL_C_CHAR string binding (GH-503), and decimalDigits uses the
+        batch-wide max scale so every row fits the declared type (a naive
+        sample-only switch regresses mixed-scale batches, GH-557 shape).
+
+        Returns True if the declaration was changed.
+        """
+        if paraminfo.paramSQLType != ddbc_sql_const.SQL_VARCHAR.value:
+            return False
+        non_nulls = [v for v in column if v is not None]
+        if not non_nulls or not all(isinstance(v, decimal.Decimal) for v in non_nulls):
+            return False
+        if not all(SMALLMONEY_MIN <= v <= MONEY_MAX for v in non_nulls):
+            return False
+        paraminfo.paramSQLType = ddbc_sql_const.SQL_NUMERIC.value
+        paraminfo.decimalDigits = max(
+            (-v.as_tuple().exponent) if v.as_tuple().exponent < 0 else 0 for v in non_nulls
+        )
+        logger.debug(
+            "executemany: money-range batch re-declared as SQL_NUMERIC, "
+            "decimalDigits=%d (GH-745)",
+            paraminfo.decimalDigits,
+        )
+        return True
+
     def executemany(  # pylint: disable=too-many-locals,too-many-branches,too-many-statements
         self,
         operation: str,
@@ -2561,6 +2593,13 @@ def executemany(  # pylint: disable=too-many-locals,too-many-branches,too-many-s
                     max_val=max_val,
                 )
 
+                # GH-745: a money-range Decimal batch declared as SQL_VARCHAR
+                # overflows on the server when compared against a smaller
+                # numeric column (the executemany remnant of GH-740). Re-declare
+                # as SQL_NUMERIC with batch-wide scale; string binding (GH-503)
+                # is preserved by the override below.
+                self._apply_money_batch_declared_type(paraminfo, column)
+
                 # GH-610: all-NULL columns now pass SQL_UNKNOWN_TYPE to C++,
                 # where BindParameterArray resolves the correct type via the
                 # SQLDescribeParam cache.  The previous SQL_VARCHAR hardcoded

tests/test_020_money_smallmoney.py

@@ -8,8 +8,9 @@
 SQL_NUMERIC using its own precision and scale, regardless of value. Binding no longer
 depends on whether the value falls in the MONEY/SMALLMONEY range, so an in-range value
 compared against a smaller numeric column returns no match instead of a varchar->numeric
-overflow (GH-740). executemany still string-binds Decimals (SQL_VARCHAR) to preserve
-scale-38 precision (GH-503), so that path is unchanged here.
+overflow (GH-740). executemany string-binds Decimals to preserve scale-38 precision
+(GH-503); a money-range batch is additionally re-declared as SQL_NUMERIC with batch-wide
+scale so the server does not overflow when coercing the strings (GH-745).
 """
 
 import pytest
@@ -528,6 +529,69 @@ def test_executemany_money_smallmoney(cursor, db_connection):
         db_connection.commit()
 
 
+class _ParamInfo:
+    """Duck-typed stand-in for ddbc_bindings.ParamInfo (no C extension needed)."""
+
+    def __init__(self, sql_type):
+        self.paramSQLType = sql_type
+        self.decimalDigits = 0
+        self.columnSize = 0
+
+
+def _bare_cursor():
+    """A Cursor instance that skips __init__ (no DB connection required)."""
+    from mssql_python.cursor import Cursor
+
+    return Cursor.__new__(Cursor)
+
+
+def test_money_batch_redeclared_as_numeric():
+    """GH-745: a money-range Decimal batch must declare SQL_NUMERIC (not the
+    VARCHAR shortcut), with decimalDigits = batch-wide max scale, so the server
+    does not overflow converting the strings. Mirrors the GH-740 fix on
+    execute(); the string binding (GH-503) is applied separately downstream."""
+    from mssql_python.constants import ConstantsDDBC as ddbc
+
+    cur = _bare_cursor()
+    varchar = ddbc.SQL_VARCHAR.value
+    numeric = ddbc.SQL_NUMERIC.value
+
+    # In-range batch, mixed scales -> redeclared NUMERIC with max scale 4
+    p = _ParamInfo(varchar)
+    assert cur._apply_money_batch_declared_type(
+        p, [Decimal("12345.6789"), Decimal("-0.0001"), None]
+    ) is True
+    assert p.paramSQLType == numeric
+    assert p.decimalDigits == 4
+
+    # Integer-valued money -> scale 0
+    p = _ParamInfo(varchar)
+    assert cur._apply_money_batch_declared_type(p, [Decimal("100"), Decimal("-2")]) is True
+    assert p.paramSQLType == numeric
+    assert p.decimalDigits == 0
+
+    # Above MONEY_MAX -> unchanged (existing NUMERIC path handles it)
+    p = _ParamInfo(varchar)
+    assert cur._apply_money_batch_declared_type(p, [Decimal("9999999999999999")]) is False
+    assert p.paramSQLType == varchar
+
+    # Mixed Decimal + str -> unchanged (not a pure Decimal column)
+    p = _ParamInfo(varchar)
+    assert cur._apply_money_batch_declared_type(p, [Decimal("1.5"), "2.5"]) is False
+    assert p.paramSQLType == varchar
+
+    # All-NULL column -> unchanged (nothing to type)
+    p = _ParamInfo(varchar)
+    assert cur._apply_money_batch_declared_type(p, [None, None]) is False
+    assert p.paramSQLType == varchar
+
+    # Already declared non-VARCHAR -> untouched
+    p = _ParamInfo(numeric)
+    assert cur._apply_money_batch_declared_type(p, [Decimal("1.5")]) is False
+    assert p.paramSQLType == numeric
+    assert p.decimalDigits == 0
+
+
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 # Invalid Input Handling
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