Overload column

docs/index.rst

@@ -143,31 +143,36 @@ Argument           Description
                    string field names for the CSV header.
 =================  =========================================================
 
-=====================  =====================================================
+=======================  =====================================================
 Keyword Arguments
-=====================  =====================================================
-``delimiter``          The character that separates values in the data file.
-                       By default  it is ",". This must be a single one-byte
-                       character.
-
-``null``               Specifies the string that represents a null value.
-                       The default is an unquoted empty string. This must
-                       be a single one-byte character.
-
-``encoding``           Specifies the character set encoding of the strings
-                       in the CSV data source.  For example, ``'latin-1'``,
-                       ``'utf-8'``, and ``'cp437'`` are all valid encoding
-                       parameters.
-
-``using``              Sets the database to use when importing data.
-                       Default is None, which will use the ``'default'``
-                       database.
-
-``static_mapping``     Set model attributes not in the CSV the same
-                       for every row in the database by providing a dictionary
-                       with the name of the columns as keys and the static
-                       inputs as values.
-=====================  =====================================================
+=======================  =====================================================
+``delimiter``            The character that separates values in the data file.
+                         By default  it is ",". This must be a single one-byte
+                         character.
+
+``null``                 Specifies the string that represents a null value.
+                         The default is an unquoted empty string. This must
+                         be a single one-byte character.
+
+``encoding``             Specifies the character set encoding of the strings
+                         in the CSV data source.  For example, ``'latin-1'``,
+                         ``'utf-8'``, and ``'cp437'`` are all valid encoding
+                         parameters.
+
+``using``                Sets the database to use when importing data.
+                         Default is None, which will use the ``'default'``
+                         database.
+
+``static_mapping``       Set model attributes not in the CSV the same
+                         for every row in the database by providing a dictionary
+                         with the name of the columns as keys and the static
+                         inputs as values.
+
+``overloaded_mapping``   Reuse a mapped column for a different model field.
+                         This is useful when you want to have both the
+                         original value as well as a modified form, generally
+                         using a `copy_template` to transform the second value
+=======================  =====================================================
 
 
 ``save()`` keyword arguments

postgres_copy/__init__.py

@@ -1,27 +1,30 @@
+import csv
 import os
 import sys
-import csv
-from django.db import connections, router
-from django.contrib.humanize.templatetags.humanize import intcomma
 from collections import OrderedDict
 
+from django.contrib.humanize.templatetags.humanize import intcomma
+from django.db import connections, router
+
 
 class CopyMapping(object):
     """
     Maps comma-delimited data file to a Django model
     and loads it into PostgreSQL databases using its
     COPY command.
     """
+
     def __init__(
-        self,
-        model,
-        csv_path,
-        mapping,
-        using=None,
-        delimiter=',',
-        null=None,
-        encoding=None,
-        static_mapping=None
+            self,
+            model,
+            csv_path,
+            mapping,
+            using=None,
+            delimiter=',',
+            null=None,
+            encoding=None,
+            static_mapping=None,
+            overloaded_mapping=None
     ):
         self.model = model
         self.mapping = mapping
@@ -44,6 +47,10 @@ def __init__(
             self.static_mapping = OrderedDict(static_mapping)
         else:
             self.static_mapping = {}
+        if overloaded_mapping is not None:
+            self.overloaded_mapping = overloaded_mapping
+        else:
+            self.overloaded_mapping = {}
 
         # Connect the headers from the CSV with the fields on the model
         self.field_header_crosswalk = []
@@ -58,13 +65,21 @@ def __init__(
             except IndexError:
                 raise ValueError("Model does not include %s field" % f_name)
             self.field_header_crosswalk.append((f, h))
-
         # Validate that the static mapping columns exist
         for f_name in self.static_mapping.keys():
             try:
                 [s for s in self.model._meta.fields if s.name == f_name][0]
             except IndexError:
                 raise ValueError("Model does not include %s field" % f_name)
+        # Validate Overloaded headers and fields
+        self.overloaded_crosswalk = []
+        for k, v in self.overloaded_mapping.items():
+            try:
+                o = [o for o in self.model._meta.fields if o.name == k][0]
+                self.overloaded_crosswalk.append((o, v))
+            except IndexError:
+                raise ValueError("Model does not include overload %s field"
+                                 % v)
 
         self.temp_table_name = "temp_%s" % self.model._meta.db_table
 
@@ -173,7 +188,7 @@ def prep_copy(self):
             'extra_options': '',
             'header_list': ", ".join([
                 '"%s"' % h for f, h in self.field_header_crosswalk
-            ])
+             ])
         }
         if self.delimiter:
             options['extra_options'] += " DELIMITER '%s'" % self.delimiter
@@ -209,19 +224,34 @@ def prep_insert(self):
         for k in self.static_mapping.keys():
             model_fields.append('"%s"' % k)
 
+        for field, value in self.overloaded_crosswalk:
+            model_fields.append('"%s"' % field.get_attname_column()[1])
+
         options['model_fields'] = ", ".join(model_fields)
 
         temp_fields = []
         for field, header in self.field_header_crosswalk:
-            string = '"%s"' % header
-            if hasattr(field, 'copy_template'):
-                string = field.copy_template % dict(name=header)
-            template_method = 'copy_%s_template' % field.name
-            if hasattr(self.model, template_method):
-                template = getattr(self.model(), template_method)()
-                string = template % dict(name=header)
-            temp_fields.append(string)
+            temp_fields.append(self._generate_insert_temp_fields(
+                field, header)
+            )
+
         for v in self.static_mapping.values():
             temp_fields.append("'%s'" % v)
+
+        for field, value in self.overloaded_crosswalk:
+            temp_fields.append(self._generate_insert_temp_fields(
+                field, value)
+            )
         options['temp_fields'] = ", ".join(temp_fields)
+
         return sql % options
+
+    def _generate_insert_temp_fields(self, concrete, column):
+        string = '"%s"' % column
+        if hasattr(concrete, 'copy_template'):
+            string = concrete.copy_template % dict(name=column)
+        template_method = 'copy_%s_template' % concrete.name
+        if hasattr(self.model, template_method):
+            template = getattr(self.model(), template_method)()
+            string = template % dict(name=column)
+        return string

tests/models.py

@@ -29,3 +29,23 @@ class Meta:
     def copy_name_template(self):
         return 'upper("%(name)s")'
     copy_name_template.copy_type = 'text'
+
+
+class OverloadMockObject(models.Model):
+    name = models.CharField(max_length=500)
+    lower_name = models.CharField(max_length=500)
+    number = MyIntegerField(null=True, db_column='num')
+    dt = models.DateField(null=True)
+    parent = models.ForeignKey('MockObject', null=True, default=None)
+
+    class Meta:
+        app_label = 'tests'
+
+    def copy_name_template(self):
+        return 'upper("%(name)s")'
+    copy_name_template.copy_type = 'text'
+
+    def copy_lower_name_template(self):
+        return 'lower("%(name)s")'
+    copy_name_template.copy_type = 'text'
+

tests/tests.py

@@ -1,6 +1,6 @@
 import os
 from datetime import date
-from .models import MockObject, ExtendedMockObject
+from .models import MockObject, ExtendedMockObject, OverloadMockObject
 from postgres_copy import CopyMapping
 from django.test import TestCase
 
@@ -18,6 +18,7 @@ def setUp(self):
     def tearDown(self):
         MockObject.objects.all().delete()
         ExtendedMockObject.objects.all().delete()
+        OverloadMockObject.objects.all().delete()
 
     def test_bad_call(self):
         with self.assertRaises(TypeError):
@@ -217,3 +218,30 @@ def test_save_foreign_key(self):
             MockObject.objects.get(name='BEN').dt,
             date(2012, 1, 1)
         )
+
+    def test_overload_save(self):
+        c = CopyMapping(
+            OverloadMockObject,
+            self.name_path,
+            dict(name='NAME', number='NUMBER', dt='DATE'),
+            overloaded_mapping=dict(lower_name='NAME')
+        )
+        c.save()
+        self.assertEqual(OverloadMockObject.objects.count(), 3)
+        self.assertEqual(OverloadMockObject.objects.get(name='BEN').number, 1)
+        self.assertEqual(OverloadMockObject.objects.get(lower_name='ben').number, 1)
+        self.assertEqual(
+            OverloadMockObject.objects.get(name='BEN').dt,
+            date(2012, 1, 1)
+        )
+        omo = OverloadMockObject.objects.first()
+        self.assertEqual(omo.name.lower(), omo.lower_name)
+
+    def test_missing_overload_field(self):
+        with self.assertRaises(ValueError):
+            c = CopyMapping(
+                OverloadMockObject,
+                self.name_path,
+                dict(name='NAME', number='NUMBER', dt='DATE'),
+                overloaded_mapping=dict(missing='NAME')
+            )