Implement support for MySQL linestring data type.

This data type is now converted automatically to a PostgreSQL path data
type, using the open path notation with square brackets:

  https://www.postgresql.org/docs/current/static/datatype-geometric.html#AEN7103

Fix #445.

src/sources/mysql/mysql-cast-rules.lisp

@@ -141,7 +141,11 @@
 
     (:source (:type "point")
      :target (:type "point")
-     :using pgloader.transforms::convert-mysql-point))
+     :using pgloader.transforms::convert-mysql-point)
+
+    (:source (:type "linestring")
+     :target (:type "path")
+     :using pgloader.transforms::convert-mysql-linestring))
   "Data Type Casting rules to migrate from MySQL to PostgreSQL")
 
 

src/sources/mysql/mysql-schema.lisp

@@ -339,9 +339,10 @@
    Mostly we just use the name, but in case of POINT we need to use
    astext(name)."
   (case (intern (string-upcase type) "KEYWORD")
-    (:geometry  (format nil "astext(`~a`) as `~a`" name name))
-    (:point     (format nil "astext(`~a`) as `~a`" name name))
-    (t          (format nil "`~a`" name))))
+    (:geometry   (format nil "astext(`~a`) as `~a`" name name))
+    (:point      (format nil "astext(`~a`) as `~a`" name name))
+    (:linestring (format nil "astext(`~a`) as `~a`" name name))
+    (t           (format nil "`~a`" name))))
 
 (defun get-column-list (dbname table-name)
   "Some MySQL datatypes have a meaningless default output representation, we

src/utils/transforms.lisp

@@ -187,6 +187,24 @@
       (setf (aref point (position #\Space point)) #\,)
       point)))
 
+(defun convert-mysql-linestring (mysql-linestring-as-string)
+  "Transform the MYSQL-POINT-AS-STRING into a suitable representation for
+   PostgreSQL.
+
+  Input:   \"LINESTRING(-87.87342467651445 45.79684462673078,-87.87170806274479 45.802110434248966)\" ; that's using astext(column)
+  Output:  [(-87.87342467651445,45.79684462673078),(-87.87170806274479,45.802110434248966)]"
+  (when mysql-linestring-as-string
+    (let* ((data (subseq mysql-linestring-as-string
+                         11
+                         (- (length mysql-linestring-as-string) 1))))
+      (with-output-to-string (s)
+        (write-string "[" s)
+        (loop :for first := t :then nil
+           :for point :in (split-sequence:split-sequence #\, data)
+           :for (x y) := (split-sequence:split-sequence #\Space point)
+           :do (format s "~:[,~;~](~a,~a)" first x y))
+        (write-string "]" s)))))
+
 (defun integer-to-string (integer-string)
   "Transform INTEGER-STRING parameter into a proper string representation of
    it. In particular be careful of quoted-integers, thanks to SQLite default