Add support for SQLite implicit pkeys.

It turns out that in some cases SQLite will not list its primary key indexes
in the pragma index_list(), and that's related to an implementation detail
about using its internal btree structure when rowid can be exploited as the
integer pkey.

Reverse engineer that bahavior in pgloader so that the PostgreSQL schema
contains the primary keys even when they are implicit. In doing that we must
be careful that the pkeys might also appear explicitely, in which case we
refrain from declaring them twice.

SQLite catalogs are not my favorite, not to say hackish as hell.

Fixes #563.

src/sources/sqlite/sqlite-schema.lisp

@@ -120,6 +120,27 @@
 ;;;
 ;;; Index support
 ;;;
+(defun add-unlisted-primary-key-index (table)
+  "Add to TABLE any unlisted primary key index..."
+  (unless (remove-if-not #'index-primary (table-index-list table))
+    (let ((pk-fields (loop :for field :in (table-field-list table)
+                        :when (< 0 (coldef-pk-id field))
+                        :collect field)))
+      (when (and pk-fields
+                 ;; we don't know if that holds true for non-integer fields,
+                 ;; as it appears to be tied to the rowid magic column
+                 (every (lambda (field)
+                          (string-equal "integer" (coldef-dtype field)))
+                        pk-fields))
+        (let ((pk-name (format nil "~a_pkey" (format-table-name table)))
+              (clist   (mapcar #'coldef-name pk-fields)))
+          ;; now forge the index and get it a name
+          (add-index table (make-index :name pk-name
+                                       :table table
+                                       :primary t
+                                       :unique t
+                                       :columns clist)))))))
+
 (defun is-index-pk (table index-col-name-list)
   "The only way to know with SQLite pragma introspection if a particular
    UNIQUE index is actually PRIMARY KEY is by comparing the list of column
@@ -148,7 +169,14 @@
                                      :primary (is-index-pk table cols)
                                      :unique (= unique 1)
                                      :columns cols)))
-             (add-index table index)))))
+             (add-index table index))))
+
+  ;; ok that's not the whole story. Integer columns marked pk=1 are actually
+  ;; primary keys but the supporting index isn't listed in index_list()
+  ;;
+  ;; we add unlisted pkeys only after having read the catalogs, otherwise we
+  ;; might create double primary key indexes here
+  (add-unlisted-primary-key-index table))
 
 (defun list-all-indexes (schema &key (db *sqlite-db*))
   "Get the list of SQLite index definitions per table."