From 6c804042490e978b1cc630395ff294be2a043914 Mon Sep 17 00:00:00 2001
From: Dimitri Fontaine <dim@tapoueh.org>
Date: Fri, 9 Nov 2018 22:41:14 +0100
Subject: [PATCH] Implement support for Redshift "identity" columns.

At this stage we don't even parse the details of the Redshift identity such
as the seed and step values and consider them the same as a MySQL
auto_increment extra description field.

Fixes #860 (again).
---
 src/pgsql/pgsql-finalize-catalogs.lisp  |  6 +++++-
 src/sources/pgsql/pgsql-cast-rules.lisp | 15 ++++++++++++---
 2 files changed, 17 insertions(+), 4 deletions(-)

diff --git a/src/pgsql/pgsql-finalize-catalogs.lisp b/src/pgsql/pgsql-finalize-catalogs.lisp
index 5a4eeef..5684100 100644
--- a/src/pgsql/pgsql-finalize-catalogs.lisp
+++ b/src/pgsql/pgsql-finalize-catalogs.lisp
@@ -15,6 +15,8 @@
 (in-package #:pgloader.pgsql)
 
 (defun finalize-catalogs (catalog variant)
+  "Finalize the target PostgreSQL catalogs, dumbing down datatypes when the
+   target actually is Redshift rather than core PostgreSQL."
   ;;
   ;; For Core PostgreSQL, we also want to find data types names that have
   ;; no Btree support and fetch alternatives. This allows for supporting
@@ -30,7 +32,9 @@
   ;;
   (adjust-data-types catalog variant))
 
-(defgeneric adjust-data-types (catalog variant))
+(defgeneric adjust-data-types (catalog variant)
+  (:documentation
+   "Adjust PostgreSQL data types depending on the variant we target."))
 
 ;;;
 ;;; Nothing needs to be done for PostgreSQL variant :pgdg, of course.
diff --git a/src/sources/pgsql/pgsql-cast-rules.lisp b/src/sources/pgsql/pgsql-cast-rules.lisp
index 6ac37ee..6c0690e 100644
--- a/src/sources/pgsql/pgsql-cast-rules.lisp
+++ b/src/sources/pgsql/pgsql-cast-rules.lisp
@@ -36,13 +36,16 @@
                pgloader.catalog::extra)
       field
     (let* ((ctype (pgsql-column-ctype field))
+           (extra (when (and (stringp (column-default field))
+                             (search "identity" (column-default field)))
+                    :auto-increment))
            (pgcol (apply-casting-rules nil
                                        pgloader.catalog::name
                                        pgloader.catalog::type-name
                                        ctype
                                        pgloader.catalog::default
                                        pgloader.catalog::nullable
-                                       pgloader.catalog::extra)))
+                                       extra)))
       ;; re-install our instruction not to transform default value: it comes
       ;; from PostgreSQL, and we trust it.
       (setf (column-transform-default pgcol)
@@ -55,10 +58,16 @@
                 ((and (stringp default) (string= "NULL" default))
                  :null)
 
-                ((and (stringp default)
-                      (or (string= "getdate()" default)))
+                ((and (stringp default) (string= "getdate()" default))
                  :current-timestamp)
 
+                ;; get rid of the identity default value, we already added
+                ;; an hint in the column-extra field.
+                ;;
+                ;; "identity"(347358, 0, ('1,1'::character varying)::text)
+                ((and (stringp default) (search "identity" default))
+                 :null)
+
                 (t (column-default pgcol))))
 
         ;; we usually trust defaults that come from PostgreSQL... but we