The error "DPY-2047: LOB amount must be greater than zero" is now raised

when the amount parameter to LOB.read() is zero or negative.

Author: anthony-tuininga

doc/src/release_notes.rst

@@ -97,6 +97,8 @@ Common Changes
     parameters if they were not included in the parameters. This also affected
     calls to :meth:`oracledb.connect()` and :meth:`oracledb.create_pool()` that
     made use of the DSN with credentials format.
+#)  The error ``DPY-2047: LOB amount must be greater than zero`` is now raised
+    when the amount parameter to :meth:`LOB.read()` is zero or negative.
 #)  Fixed bug in the calculation of :data:`Cursor.rowcount` under some
     circumstances.
 #)  Connection parameters that are strings now treat an empty string in the

src/oracledb/errors.py

@@ -240,6 +240,7 @@ def _raise_err(
 ERR_DBOBJECT_ELEMENT_MAX_SIZE_VIOLATED = 2044
 ERR_INVALID_ARRAYSIZE = 2045
 ERR_CURSOR_HAS_BEEN_CLOSED = 2046
+ERR_INVALID_LOB_AMOUNT = 2047
 
 # error numbers that result in NotSupportedError
 ERR_TIME_NOT_SUPPORTED = 3000
@@ -520,6 +521,7 @@ def _raise_err(
         "given index {index} must be in the range of {min_index} to "
         "{max_index}"
     ),
+    ERR_INVALID_LOB_AMOUNT: "LOB amount must be greater than zero",
     ERR_INVALID_LOB_OFFSET: "LOB offset must be greater than zero",
     ERR_INVALID_MAKEDSN_ARG: '"{name}" argument contains invalid values',
     ERR_INVALID_NUMBER: "invalid number",

src/oracledb/lob.py

@@ -145,6 +145,8 @@ def read(self, offset: int = 1, amount: int = None) -> Union[str, bytes]:
                 amount = amount - offset + 1
             else:
                 amount = 1
+        elif amount <= 0:
+            errors._raise_err(errors.ERR_INVALID_LOB_AMOUNT)
         if offset <= 0:
             errors._raise_err(errors.ERR_INVALID_LOB_OFFSET)
         return self._impl.read(offset, amount)

tests/test_1900_lob_var.py

@@ -181,6 +181,10 @@ def __test_lob_operations(self, lob_type):
             lob.read(0)
         with self.assertRaisesFullCode("DPY-2030"):
             lob.read(-25)
+        with self.assertRaisesFullCode("DPY-2047"):
+            lob.read(amount=0)
+        with self.assertRaisesFullCode("DPY-2047"):
+            lob.read(amount=-5)
         self.assertEqual(lob.read(), long_string + write_value)
         lob.write(write_value, 1)
         self.assertEqual(