From 9697f5553436a625fba1fb7c2fe5542868998280 Mon Sep 17 00:00:00 2001
From: Thomas Waldmann <tw@waldmann-edv.de>
Date: Wed, 8 Feb 2023 01:53:30 +0100
Subject: [PATCH 1/2] add hashtable stress tests

Using NSIndex (repo index) HashIndex, but they all are very similar.
---
 src/borg/testsuite/hashindex_stress.py | 32 ++++++++++++++++++++++++++
 1 file changed, 32 insertions(+)
 create mode 100644 src/borg/testsuite/hashindex_stress.py

diff --git a/src/borg/testsuite/hashindex_stress.py b/src/borg/testsuite/hashindex_stress.py
new file mode 100644
index 000000000..4b938368a
--- /dev/null
+++ b/src/borg/testsuite/hashindex_stress.py
@@ -0,0 +1,32 @@
+import os
+import random
+
+import pytest
+
+from ..hashindex import NSIndex
+
+
+@pytest.mark.skipif("BORG_TESTS_SLOW" not in os.environ, reason="slow tests not enabled, use BORG_TESTS_SLOW=1")
+def test_hashindex_stress():
+    """checks if the hashtable behaves as expected"""
+    ENTRIES = 10000
+    LOOPS = 100
+    idx = NSIndex()
+    kv = {}
+    for i in range(LOOPS):
+        # put some entries
+        for j in range(ENTRIES):
+            k = random.randbytes(32)
+            v = random.randint(0, NSIndex.MAX_VALUE - 1)
+            idx[k] = (v, v, v)
+            kv[k] = v
+        # check and delete a random amount of entries
+        delete_keys = random.sample(list(kv), k=random.randint(0, len(kv)))
+        for k in delete_keys:
+            v = kv.pop(k)
+            assert idx.pop(k) == (v, v, v)
+        # check if remaining entries are as expected
+        for k, v in kv.items():
+            assert idx[k] == (v, v, v)
+        # check entry count
+        assert len(kv) == len(idx)

From 3e336562385c34de4b6f4b26e2eb9f1ee48da169 Mon Sep 17 00:00:00 2001
From: Thomas Waldmann <tw@waldmann-edv.de>
Date: Wed, 8 Feb 2023 02:10:38 +0100
Subject: [PATCH 2/2] add comment about how to provoke more collisions

---
 src/borg/testsuite/hashindex_stress.py | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/src/borg/testsuite/hashindex_stress.py b/src/borg/testsuite/hashindex_stress.py
index 4b938368a..5cf8b75e1 100644
--- a/src/borg/testsuite/hashindex_stress.py
+++ b/src/borg/testsuite/hashindex_stress.py
@@ -8,9 +8,14 @@ from ..hashindex import NSIndex
 
 @pytest.mark.skipif("BORG_TESTS_SLOW" not in os.environ, reason="slow tests not enabled, use BORG_TESTS_SLOW=1")
 def test_hashindex_stress():
-    """checks if the hashtable behaves as expected"""
+    """checks if the hashtable behaves as expected
+
+    This can be used in _hashindex.c before running this test to provoke more collisions (don't forget to compile):
+    #define HASH_MAX_LOAD .99
+    #define HASH_MAX_EFF_LOAD .999
+    """
     ENTRIES = 10000
-    LOOPS = 100
+    LOOPS = 1000
     idx = NSIndex()
     kv = {}
     for i in range(LOOPS):