From 43b5bcbc7c754550328829ba649d1353fd755efc Mon Sep 17 00:00:00 2001
From: jiangph <jiangph@cn.ibm.com>
Date: Fri, 2 Nov 2018 17:12:10 +0800
Subject: Support out-of-sync in mango when doc is deleted

  - under situation where the document is deleted while the mrview
  index for this document is not updated, the returned value from
  mrview is {doc,null}. There is no such consideration in Mango to
  cause case_clause error. This fix is to consider out-of-sync between
  documents in database and their index and not to cause 500 when
  the _find endpoint is called.
---
 src/mango/src/mango_cursor_view.erl  | 13 ++++++++++++-
 src/mango/test/01-index-crud-test.py | 35 +++++++++++++++++++++++++++++++++++
 src/mango/test/mango.py              | 10 +++++++++-
 3 files changed, 56 insertions(+), 2 deletions(-)

diff --git a/src/mango/src/mango_cursor_view.erl b/src/mango/src/mango_cursor_view.erl
index 174381e4a..4d4b6e05f 100644
--- a/src/mango/src/mango_cursor_view.erl
+++ b/src/mango/src/mango_cursor_view.erl
@@ -229,6 +229,9 @@ view_cb({row, Row}, #mrargs{extra = Options} = Acc) ->
         doc = couch_util:get_value(doc, Row)
     },
     case ViewRow#view_row.doc of
+        null ->
+            put(mango_docs_examined, get(mango_docs_examined) + 1),
+            maybe_send_mango_ping();
         undefined ->
             ViewRow2 = ViewRow#view_row{
                 value = couch_util:get_value(value, Row)
@@ -282,6 +285,11 @@ handle_message({meta, _}, Cursor) ->
     {ok, Cursor};
 handle_message({row, Props}, Cursor) ->
     case doc_member(Cursor, Props) of
+        {ok, null, {execution_stats, ExecutionStats1}} ->
+            Cursor1 = Cursor#cursor {
+                execution_stats = ExecutionStats1
+            },
+            {ok, Cursor1};
         {ok, Doc, {execution_stats, ExecutionStats1}} ->
             Cursor1 = Cursor#cursor {
                 execution_stats = ExecutionStats1
@@ -427,7 +435,10 @@ doc_member(Cursor, RowProps) ->
                     match_doc(Selector, Doc, ExecutionStats1);
                 Else ->
                     Else
-            end
+            end;
+        null ->
+            ExecutionStats1 = mango_execution_stats:incr_docs_examined(ExecutionStats),
+            {ok, null, {execution_stats, ExecutionStats1}}
     end.
 
 
diff --git a/src/mango/test/01-index-crud-test.py b/src/mango/test/01-index-crud-test.py
index cf5b91865..7bc090abe 100644
--- a/src/mango/test/01-index-crud-test.py
+++ b/src/mango/test/01-index-crud-test.py
@@ -13,8 +13,24 @@
 import random
 
 import mango
+import copy
 import unittest
 
+DOCS = [
+    {
+        "_id": "1",
+        "name": "Jimi",
+        "age": 10,
+        "cars": 1
+    },
+    {
+        "_id": "2",
+        "name": "kate",
+        "age": 8,
+        "cars": 0
+    }
+]
+
 class IndexCrudTests(mango.DbPerClass):
     def setUp(self):
         self.db.recreate()
@@ -271,6 +287,25 @@ class IndexCrudTests(mango.DbPerClass):
         except Exception as e:
             self.assertEqual(e.response.status_code, 500)
 
+    def test_out_of_sync(self):
+        self.db.save_docs(copy.deepcopy(DOCS))
+        self.db.create_index(["age"], name="age")
+
+        selector = {
+            "age": {
+                "$gt": 0
+            },
+        }
+        docs = self.db.find(selector,
+            use_index="_design/a017b603a47036005de93034ff689bbbb6a873c4")
+        self.assertEqual(len(docs), 2)
+
+        self.db.delete_doc("1")
+
+        docs1 = self.db.find(selector, stale="ok",
+            use_index="_design/a017b603a47036005de93034ff689bbbb6a873c4")
+        self.assertEqual(len(docs1), 1)
+
 
 @unittest.skipUnless(mango.has_text_service(), "requires text service")
 class IndexCrudTextTests(mango.DbPerClass):
diff --git a/src/mango/test/mango.py b/src/mango/test/mango.py
index bc12bbc68..29c003cc6 100644
--- a/src/mango/test/mango.py
+++ b/src/mango/test/mango.py
@@ -113,6 +113,12 @@ class Database(object):
         r.raise_for_status()
         return r.json()
 
+    def delete_doc(self, docid):
+        r = self.sess.get(self.path(docid))
+        r.raise_for_status()
+        original_rev = r.json()['_rev']
+        self.sess.delete(self.path(docid), params={"rev": original_rev})
+
     def ddoc_info(self, ddocid):
         r = self.sess.get(self.path([ddocid, "_info"]))
         r.raise_for_status()
@@ -220,7 +226,7 @@ class Database(object):
 
     def find(self, selector, limit=25, skip=0, sort=None, fields=None,
                 r=1, conflicts=False, use_index=None, explain=False,
-                bookmark=None, return_raw=False, update=True, executionStats=False):
+                bookmark=None, return_raw=False, update=True, executionStats=False, stale=None):
         body = {
             "selector": selector,
             "use_index": use_index,
@@ -239,6 +245,8 @@ class Database(object):
             body["update"] = False
         if executionStats == True:
             body["execution_stats"] = True
+        if stale is not None:
+            body["stale"] = stale
         body = json.dumps(body)
         if explain:
             path = self.path("_explain")
-- 
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