From cea032ecb83a589be94860f6045c55533237c529 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Ren=C3=A9=20=27Necoro=27=20Neumann?= <necoro@necoro.net>
Date: Tue, 3 Oct 2017 22:07:57 +0200
Subject: Unique index on tags as a functional one. See also:
 https://github.com/coleifer/peewee/issues/1357

---
 archivist/model.py      |  6 ++++--
 archivist/peewee_ext.py | 17 ++++++++++++++++-
 2 files changed, 20 insertions(+), 3 deletions(-)

diff --git a/archivist/model.py b/archivist/model.py
index f03927e..8aa8897 100644
--- a/archivist/model.py
+++ b/archivist/model.py
@@ -7,7 +7,7 @@ import datetime
 from enum import Enum, unique
 from pkg_resources import resource_filename
 
-from .peewee_ext import EnumField
+from .peewee_ext import EnumField, SQLIndex
 from .peewee_fixes import * # dummy to force evaluation of those fixes
 
 db = SqliteExtDatabase('test.db', pragmas=[('foreign_keys', 'ON')])
@@ -122,6 +122,7 @@ class Prefix(BaseModel):
 @table
 class Tag(BaseModel):
     __keys__ = ('name', 'prefix')
+
     name = CharField()
     prefix = ForeignKeyField(Prefix, null=True, related_name = 'tag', db_column = 'prefix')
     description = CharField(null=True)
@@ -140,7 +141,8 @@ class Tag(BaseModel):
 
     class Meta:
         indexes = [
-            (('name', 'prefix'), True)
+            (('name', 'prefix'), False),
+            (('name', SQLIndex('coalescePrefix', "COALESCE(prefix,'')")), True)
         ]
 
     @property
diff --git a/archivist/peewee_ext.py b/archivist/peewee_ext.py
index 40fe5e7..ff03861 100644
--- a/archivist/peewee_ext.py
+++ b/archivist/peewee_ext.py
@@ -1,4 +1,4 @@
-from peewee import Field
+from peewee import Field, SQL
 
 from itertools import starmap
 from functools import reduce
@@ -42,3 +42,18 @@ class EnumField(Field):
     def python_value(self, value):
         return value if value is None else self._enum_value(value)
 
+class SQLIndex(SQL):
+    """Ugly hack to allow arbitrary index creation."""
+    def __init__(self, field, sql):
+        self.field = field
+        super().__init__(sql)
+
+    def clone_base(self):
+        return SQLWithField(field, self.value)
+
+    @property
+    def db_column(self):
+        return self.field
+
+    def as_entity(self):
+        return self
-- 
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