Remove doc limit for stats query (#1597)

## Remove doc limit for stats query
Two minor changes to the search lambda:
1. removing the document-per-shard limit only for the stats query, which can take advantage of cached summary statistics insdie elastic.
2. allow the MAX_DOCS_PER_SHARD to be set in the environment.

Small test fix:
Grabbing environment variables at initialization doesn't work (at least in pytest). Moving it into the body of the lambda handler.


Co-authored-by: Kevin Moore <kevin@quiltdata.io>

lambdas/search/index.py

@@ -11,9 +11,7 @@
 from t4_lambda_shared.decorator import api
 from t4_lambda_shared.utils import get_default_origins, make_json_response
 
-INDEX_OVERRIDES = os.getenv('INDEX_OVERRIDES', '')
 MAX_QUERY_DURATION = '15s'
-MAX_DOCUMENTS_PER_SHARD = 10000
 NUM_PREVIEW_IMAGES = 100
 NUM_PREVIEW_FILES = 100
 IMG_EXTS = [
@@ -46,8 +44,10 @@ def lambda_handler(request):
     """
     Proxy the request to the elastic search.
     """
+
     action = request.args.get('action')
     indexes = request.args.get('index')
+    terminate_after = os.getenv('MAX_DOCUMENTS_PER_SHARD')
 
     if action == 'search':
         query = request.args.get('query', '')
@@ -75,6 +75,8 @@ def lambda_handler(request):
         }
         size = 0
         _source = []
+        # Consider all documents when computing counts, etc.
+        terminate_after = None
     elif action == 'images':
         body = {
             'query': {'terms': {'ext': IMG_EXTS}},
@@ -118,7 +120,8 @@ def lambda_handler(request):
 
     es_host = os.environ['ES_HOST']
     region = os.environ['AWS_REGION']
-
+    index_overrides = os.getenv('INDEX_OVERRIDES', '')
+
     auth = BotoAWSRequestsAuth(
         aws_host=es_host,
         aws_region=region,
@@ -133,13 +136,13 @@ def lambda_handler(request):
         connection_class=RequestsHttpConnection
     )
 
-    to_search = f"{indexes},{INDEX_OVERRIDES}" if INDEX_OVERRIDES else indexes
+    to_search = f"{indexes},{index_overrides}" if index_overrides else indexes
     result = es_client.search(
         to_search,
         body,
         _source=_source,
         size=size,
-        terminate_after=MAX_DOCUMENTS_PER_SHARD,
+        terminate_after=terminate_after,
         timeout=MAX_QUERY_DURATION
     )
 

lambdas/search/tests/test_search.py

@@ -19,7 +19,8 @@ def setUp(self):
             'AWS_ACCESS_KEY_ID': 'test_key',
             'AWS_SECRET_ACCESS_KEY': 'test_secret',
             'AWS_REGION': 'ng-north-1',
-            'ES_HOST': 'www.example.com'
+            'ES_HOST': 'www.example.com',
+            'MAX_DOCUMENTS_PER_SHARD': '10000',
         })
         self.env_patcher.start()
 
@@ -86,7 +87,6 @@ def _callback(request):
     def test_stats(self):
         url = 'https://www.example.com:443/bucket/_search?' + urlencode(dict(
             timeout='15s',
-            terminate_after=10000,
             size=0,
             _source = '',
         ))