Support inspection of computed column

Added support for reflection of "computed" columns, which are now returned
as part of the structure returned by :meth:`.Inspector.get_columns`.
When reflecting full :class:`.Table` objects, computed columns will
be represented using the :class:`.Computed` construct.

Also improve the documentation in :meth:`Inspector.get_columns`, correctly
listing all the returned keys.

Fixes: #5063
Fixes: #4051

Closes: #5064
Pull-request: https://github.com/sqlalchemy/sqlalchemy/pull/5064
Pull-request-sha: ba00fc321ce468f8885aad23b3dd33c789e50fbe

Change-Id: I789986554fc8ac7f084270474d0b2c12046b1cc2

1 files changed, 24 insertions, 1 deletions

diff --git a/lib/sqlalchemy/engine/reflection.py b/lib/sqlalchemy/engine/reflection.py
index 25538fddb..ba60d634e 100644
--- a/lib/sqlalchemy/engine/reflection.py
+++ b/lib/sqlalchemy/engine/reflection.py
@@ -419,7 +419,26 @@ class Inspector(object):
         * ``default`` - the column's server default value - this is returned
           as a string SQL expression.
 
-        * ``attrs``  - dict containing optional column attributes
+        * ``autoincrement`` - indicates that the column is auto incremented -
+          this is returned as a boolean or 'auto'
+
+        * ``comment`` - (optional) the commnet on the column. Only some
+          dialects return this key
+
+        * ``computed`` - (optional) when present it indicates that this column
+          is computed by the database. Only some dialects return this key.
+          Returned as a dict with the keys:
+
+          * ``sqltext`` - the expression used to generate this column returned
+            as a string SQL expression
+
+          * ``persisted`` - (optional) boolean that indicates if the column is
+            stored in the table
+
+          .. versionadded:: 1.3.16 - added support for computed reflection.
+
+        * ``dialect_options`` - (optional) a dict with dialect specific options
+
 
         :param table_name: string name of the table.  For special quoting,
          use :class:`.quoted_name`.
@@ -825,6 +844,10 @@ class Inspector(object):
 
             colargs.append(default)
 
+        if "computed" in col_d:
+            computed = sa_schema.Computed(**col_d["computed"])
+            colargs.append(computed)
+
         if "sequence" in col_d:
             self._reflect_col_sequence(col_d, colargs)