feat: make get_table_comment work on OS390 and AS400 (#176)

Fixes #174

Signed-off-by: Michael Maltese <[email protected]>

Author: ligfx

ibm_db_sa/reflection.py

@@ -511,6 +511,7 @@ class AS400Reflector(BaseReflector):
       Column("TABLE_SCHEMA", CoerceUnicode, key="tabschema"),
       Column("TABLE_NAME", CoerceUnicode, key="tabname"),
       Column("TABLE_TYPE", CoerceUnicode, key="tabtype"),
+      Column("LONG_COMMENT", CoerceUnicode, key="remarks"),
       schema="QSYS2")
 
     sys_table_constraints = Table("SYSCST", ischema,
@@ -615,7 +616,13 @@ def has_sequence(self, connection, sequence_name, schema=None):
         return c.first() is not None
 
     def get_table_comment(self, connection, table_name, schema=None, **kw):
-        raise NotImplementedError()
+        current_schema = self.denormalize_name(schema or self.default_schema_name)
+        table_name = self.denormalize_name(table_name)
+        systbl = self.sys_tables
+        query = sql.select(systbl.c.remarks).\
+            where(systbl.c.tabschema == current_schema).\
+            where(systbl.c.tabname == table_name)
+        return {'text': connection.execute(query).scalar()}
 
     @reflection.cache
     def get_sequence_names(self, connection, schema=None, **kw):
@@ -883,6 +890,7 @@ class OS390Reflector(BaseReflector):
         Column("OWNERTYPE", CoerceUnicode, key="ownertype"),
         Column("TYPE", CoerceUnicode, key="type"),
         Column("STATUS", CoerceUnicode, key="status"),
+        Column("REMARKS", CoerceUnicode, key="remarks"),
         schema="SYSIBM")
 
     sys_indexes = Table("SYSINDEXES", ischema,
@@ -992,7 +1000,13 @@ def get_schema_names(self, connection, **kw):
         return [self.normalize_name(r[0]) for r in connection.execute(query)]
 
     def get_table_comment(self, connection, table_name, schema=None, **kw):
-        raise NotImplementedError()
+        current_schema = self.denormalize_name(schema or self.default_schema_name)
+        table_name = self.denormalize_name(table_name)
+        systbl = self.sys_tables
+        query = sql.select(systbl.c.remarks).\
+            where(systbl.c.tabschema == current_schema).\
+            where(systbl.c.tabname == table_name)
+        return {'text': connection.execute(query).scalar()}
 
     @reflection.cache
     def get_table_names(self, connection, schema=None, **kw):