Add support for getting the maximum identifier length for a database

connection (#395).

Author: anthony-tuininga

doc/src/api_manual/async_connection.rst

@@ -526,6 +526,15 @@ AsyncConnection Attributes
         This attribute is only available when Oracle Database 12.1 or later is
         in use
 
+.. attribute:: AsyncConnection.max_identifier_length
+
+    This read-only attribute specifies the maximum length of bytes supported by
+    the database to which the connection has been established.  See `Database
+    Object Naming Rules <https://www.oracle.com/pls/topic/lookup?ctx=dblatest&
+    id=GUID-75337742-67FD-4EC0-985F-741C93D918DA>`__.
+
+    .. versionadded:: 2.5.0
+
 .. attribute:: AsyncConnection.max_open_cursors
 
     This read-only attribute specifies the maximum number of cursors that the

doc/src/api_manual/connection.rst

@@ -755,6 +755,14 @@ Connection Attributes
         available when Oracle Database 12.1 or higher is in use on both the
         server and the client.
 
+.. attribute:: Connection.max_identifier_length
+
+    This read-only attribute specifies the maximum length of bytes supported
+    by the database to which the connection has been established.  See `Database
+    Object Naming Rules <https://www.oracle.com/pls/topic/lookup?ctx=dblatest&
+    id=GUID-75337742-67FD-4EC0-985F-741C93D918DA>`__.
+
+    .. versionadded:: 2.5.0
 
 .. attribute:: Connection.max_open_cursors
 

doc/src/release_notes.rst

@@ -75,6 +75,9 @@ Thick Mode Changes
 Common Changes
 ++++++++++++++
 
+#)  Added support for returning the maximum identifier length allowed by the
+    database using the new property :data:`Connection.max_identifier_length`
+    (`issue 395 <https://github.com/oracle/python-oracledb/issues/395>`__).
 #)  Improved type hints for cursors
     (`issue 391 <https://github.com/oracle/python-oracledb/issues/391>`__).
 #)  Improved error message when attempting to access attributes on a connection

src/oracledb/connection.py

@@ -350,6 +350,15 @@ def ltxid(self) -> bytes:
         self._verify_connected()
         return self._impl.get_ltxid()
 
+    @property
+    def max_identifier_length(self) -> int:
+        """
+        Returns the maximum length of identifiers supported by the database to
+        which this connection has been established.
+        """
+        self._verify_connected()
+        return self._impl.get_max_identifier_length()
+
     @property
     def max_open_cursors(self) -> int:
         """

src/oracledb/impl/base/connection.pyx

@@ -270,6 +270,9 @@ cdef class BaseConnImpl:
     def get_ltxid(self):
         errors._raise_not_supported("getting the logical transaction id")
 
+    def get_max_identifier_length(self):
+        errors._raise_not_supported("getting the maximum identifier length")
+
     def get_max_open_cursors(self):
         errors._raise_not_supported(
             "getting the maximum number of open cursors"

src/oracledb/impl/thick/connection.pyx

@@ -664,6 +664,12 @@ cdef class ThickConnImpl(BaseConnImpl):
             _raise_from_odpi()
         return value[:value_length]
 
+    def get_max_identifier_length(self):
+        cdef dpiConnInfo info
+        if dpiConn_getInfo(self._handle, &info) < 0:
+            _raise_from_odpi()
+        return info.maxIdentifierLength
+
     def get_max_open_cursors(self):
         cdef uint32_t value
         if dpiConn_getMaxOpenCursors(self._handle, &value) < 0:

src/oracledb/impl/thick/odpi.pxd

@@ -337,6 +337,19 @@ cdef extern from "impl/thick/odpi/embed/dpi.c":
         uint8_t numSuperShardingKeyColumns
         bint outNewSession
 
+    ctypedef struct dpiConnInfo:
+        const char *dbDomain
+        uint32_t dbDomainLength
+        const char *dbName
+        uint32_t dbNameLength
+        const char *instanceName
+        uint32_t instanceNameLength
+        const char *serviceName
+        uint32_t serviceNameLength
+        uint32_t maxIdentifierLength
+        uint32_t maxOpenCursors
+        uint8_t serverType
+
     ctypedef struct dpiContextCreateParams:
         const char *defaultDriverName
         const char *defaultEncoding
@@ -619,6 +632,8 @@ cdef extern from "impl/thick/odpi/embed/dpi.c":
 
     int dpiConn_getHandle(dpiConn *conn, void **handle) nogil
 
+    int dpiConn_getInfo(dpiConn *conn, dpiConnInfo *info) nogil
+
     int dpiConn_getInstanceName(dpiConn *conn, const char **value,
             uint32_t *valueLength) nogil
 

src/oracledb/impl/thin/connection.pyx

@@ -50,6 +50,7 @@ cdef class BaseThinConnImpl(BaseConnImpl):
         bytes _ltxid
         str _current_schema
         bint _current_schema_modified
+        uint8_t _max_identifier_length
         uint32_t _max_open_cursors
         str _db_domain
         str _db_name
@@ -241,6 +242,9 @@ cdef class BaseThinConnImpl(BaseConnImpl):
     def get_ltxid(self):
         return self._ltxid or b''
 
+    def get_max_identifier_length(self):
+        return self._max_identifier_length
+
     def get_max_open_cursors(self):
         return self._max_open_cursors
 

src/oracledb/impl/thin/messages.pyx

@@ -1639,6 +1639,8 @@ cdef class AuthMessage(Message):
                     self.session_data.get("AUTH_SC_SERVICE_NAME")
             self.conn_impl._instance_name = \
                     self.session_data.get("AUTH_INSTANCENAME")
+            self.conn_impl._max_identifier_length = \
+                    int(self.session_data.get("AUTH_MAX_IDEN_LENGTH", 30))
             self.conn_impl.server_version = self._get_version_tuple(buf)
             self.conn_impl.supports_bool = \
                     buf._caps.ttc_field_version >= TNS_CCAP_FIELD_VERSION_23_1

utils/templates/connection.py

@@ -348,6 +348,15 @@ def ltxid(self) -> bytes:
         self._verify_connected()
         return self._impl.get_ltxid()
 
+    @property
+    def max_identifier_length(self) -> int:
+        """
+        Returns the maximum length of identifiers supported by the database to
+        which this connection has been established.
+        """
+        self._verify_connected()
+        return self._impl.get_max_identifier_length()
+
     @property
     def max_open_cursors(self) -> int:
         """