Comment supportpr_github_284

Implementation of [#1546 (BitBucket)](https://bitbucket.org/zzzeek/sqlalchemy/issues/1546).

Very unfinished but I have reflection and setting after table creation working for PostgreSQL.

If you're not opposed, perhaps best to continue discussion on Gerrit?

Change-Id: Ib90683850805a2b4ee198e420dc294f32f15d35d
Pull-request: https://github.com/zzzeek/sqlalchemy/pull/284

3 files changed, 72 insertions, 0 deletions

diff --git a/lib/sqlalchemy/sql/compiler.py b/lib/sqlalchemy/sql/compiler.py
index 6d9ab9039..b26b0d1a7 100644
--- a/lib/sqlalchemy/sql/compiler.py
+++ b/lib/sqlalchemy/sql/compiler.py
@@ -2396,6 +2396,28 @@ class DDLCompiler(Compiled):
             self.process(create.element)
         )
 
+    def visit_set_table_comment(self, create):
+        return "COMMENT ON TABLE %s IS %s" % (
+            self.preparer.format_table(create.element),
+            self.sql_compiler.render_literal_bindparam(
+                elements.BindParameter('comment', value=create.comment))
+        )
+
+    def visit_drop_table_comment(self, drop):
+        return "COMMENT ON TABLE %s IS NULL" % \
+            self.preparer.format_table(drop.element)
+
+    def visit_set_column_comment(self, create):
+        return "COMMENT ON COLUMN %s IS %s" % (
+            self.preparer.format_column(create.element, use_table=True),
+            self.sql_compiler.render_literal_bindparam(
+                elements.BindParameter('comment', value=create.comment))
+        )
+
+    def visit_drop_column_comment(self, drop):
+        return "COMMENT ON COLUMN %s IS NULL" % \
+            self.preparer.format_column(drop.element, use_table=True)
+
     def visit_create_sequence(self, create):
         text = "CREATE SEQUENCE %s" % \
             self.preparer.format_sequence(create.element)
diff --git a/lib/sqlalchemy/sql/ddl.py b/lib/sqlalchemy/sql/ddl.py
index 48f27b8b8..79fbc8ed6 100644
--- a/lib/sqlalchemy/sql/ddl.py
+++ b/lib/sqlalchemy/sql/ddl.py
@@ -486,6 +486,15 @@ class CreateTable(_CreateDropBase):
                         ]
         self.include_foreign_key_constraints = include_foreign_key_constraints
 
+        if element.comment is not None:
+            event.listen(element, 'after_create',
+                         SetTableComment(element, element.comment))
+
+        for col in element.columns:
+            if col.comment is not None:
+                event.listen(element, 'after_create',
+                             SetColumnComment(col, col.comment))
+
 
 class _DropView(_CreateDropBase):
     """Semi-public 'DROP VIEW' construct.
@@ -661,6 +670,42 @@ class DropConstraint(_CreateDropBase):
             self._create_rule_disable)
 
 
+class SetTableComment(_CreateDropBase):
+    """Represent a COMMENT ON TABLE IS statement."""
+
+    __visit_name__ = "set_table_comment"
+
+    def __init__(self, element, comment, **kw):
+        self.comment = comment
+        super(SetTableComment, self).__init__(element, **kw)
+        element._create_rule = util.portable_instancemethod(
+            self._create_rule_disable)
+
+
+class DropTableComment(_CreateDropBase):
+    """Represent a COMMENT ON TABLE IS NULL statement."""
+
+    __visit_name__ = "drop_table_comment"
+
+
+class SetColumnComment(_CreateDropBase):
+    """Represent a COMMENT ON COLUMN IS statement."""
+
+    __visit_name__ = "set_column_comment"
+
+    def __init__(self, element, comment, **kw):
+        self.comment = comment
+        super(SetColumnComment, self).__init__(element, **kw)
+        element._create_rule = util.portable_instancemethod(
+            self._create_rule_disable)
+
+
+class DropColumnComment(_CreateDropBase):
+    """Represent a COMMENT ON COLUMN IS NULL statement."""
+
+    __visit_name__ = "drop_column_comment"
+
+
 class DDLBase(SchemaVisitor):
     def __init__(self, connection):
         self.connection = connection
diff --git a/lib/sqlalchemy/sql/schema.py b/lib/sqlalchemy/sql/schema.py
index cb01a49e3..ede9c7944 100644
--- a/lib/sqlalchemy/sql/schema.py
+++ b/lib/sqlalchemy/sql/schema.py
@@ -490,6 +490,7 @@ class Table(DialectKWArgs, SchemaItem, TableClause):
         include_columns = kwargs.pop('include_columns', None)
 
         self.implicit_returning = kwargs.pop('implicit_returning', True)
+        self.comment = kwargs.pop('comment', None)
 
         if 'info' in kwargs:
             self.info = kwargs.pop('info')
@@ -579,6 +580,9 @@ class Table(DialectKWArgs, SchemaItem, TableClause):
         if 'info' in kwargs:
             self.info = kwargs.pop('info')
 
+        if 'comment' in kwargs:
+            self.comment = kwargs.pop('comment')
+
         if autoload:
             if not autoload_replace:
                 exclude_columns = [c.name for c in self.c]
@@ -1176,6 +1180,7 @@ class Column(SchemaItem, ColumnClause):
         self.autoincrement = kwargs.pop('autoincrement', "auto")
         self.constraints = set()
         self.foreign_keys = set()
+        self.comment = kwargs.pop('comment', None)
 
         # check if this Column is proxying another column
         if '_proxies' in kwargs: