Add ability to configure explain command options (#49)

Author: juliusgeo

README.rst

@@ -93,6 +93,16 @@ To run explain on a command, first instantiate an ``ExplainableCollection`` from
     collection = client.db.products
     explain = ExplainableCollection(collection)
 
+If you wish to configure the options for the explain command itself, pass
+them to the ``ExplainableCollection`` constructor like so::
+
+    explain = ExplainableCollection(collection, verbosity="queryPlanner",
+                                    comment="I'm a comment")
+
+For more information see the documentation for the explain_ command.
+
+.. _explain: https://docs.mongodb.com/master/reference/command/explain/#dbcmd.explain.
+
 Now you are ready to explain some commands. Remember that explaining a command does not execute it::
 
     result = explain.update_one({"quantity": 1057, "category": "apparel"}, {"$set": {"reorder": True}})

pymongoexplain/explainable_collection.py

@@ -26,14 +26,18 @@
 
 
 class ExplainableCollection():
-    def __init__(self, collection):
+    def __init__(self, collection, verbosity=None, comment=None):
         self.collection = collection
         self.last_cmd_payload = None
+        self.verbosity = verbosity or "queryPlanner"
+        self.comment = comment
 
     def _explain_command(self, command):
         command_son = command.get_SON()
         explain_command = SON([("explain", command_son)])
-        explain_command["verbosity"] = "queryPlanner"
+        explain_command["verbosity"] = self.verbosity
+        if self.comment:
+            explain_command["comment"] = self.comment
         self.last_cmd_payload = command_son
         return self.collection.database.command(explain_command)
 

test/test_collection.py

@@ -12,7 +12,6 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-
 import unittest
 import subprocess
 import os
@@ -28,6 +27,7 @@
 class CommandLogger(monitoring.CommandListener):
     def __init__(self):
         self.cmd_payload = {}
+
     def started(self, event):
         self.cmd_payload = event.command
 
@@ -37,6 +37,7 @@ def succeeded(self, event):
     def failed(self, event):
         pass
 
+
 class TestExplainableCollection(unittest.TestCase):
     def setUp(self) -> None:
         self.logger = CommandLogger()
@@ -217,6 +218,25 @@ def test_imports(self):
         from pymongoexplain import ExplainableCollection
         self.assertEqual(ExplainableCollection, ExplainCollection)
 
+    def test_verbosity(self):
+        res = self.explain.find({})
+        self.assertNotIn("executionStats", res)
+        self.assertNotIn("allPlansExecution", res.get("executionStats", []))
+        self.explain = ExplainCollection(self.collection, verbosity="executionStats")
+        res = self.explain.find({})
+        self.assertIn("executionStats", res)
+        self.assertNotIn("allPlansExecution", res["executionStats"])
+        self.explain = ExplainCollection(self.collection, verbosity="allPlansExecution")
+        res = self.explain.find({})
+        self.assertIn("executionStats", res)
+        self.assertIn("allPlansExecution", res["executionStats"])
+
+    def test_comment(self):
+        self.explain.find({})
+        self.assertNotIn("comment", self.logger.cmd_payload)
+        self.explain = ExplainCollection(self.collection, comment="comment")
+        self.explain.find({})
+        self.assertIn("comment", self.logger.cmd_payload)
 
 if __name__ == '__main__':
     unittest.main()