From d7f9bfdfc521b71b70fc610855d0c389987bf86e Mon Sep 17 00:00:00 2001
From: raphael claude <charlesalbert.claude@gmail.com>
Date: Sun, 20 Aug 2017 01:59:54 +0200
Subject: [PATCH] fix segments sorting in log_merge_policy (#211)

bug: segments were sorted on their indices (first field in the tuples)
fix: sort on the segments size
---
 src/indexer/log_merge_policy.rs | 27 ++++++++++++++++++---------
 1 file changed, 18 insertions(+), 9 deletions(-)

diff --git a/src/indexer/log_merge_policy.rs b/src/indexer/log_merge_policy.rs
index 47f496998..f565e5ae1 100644
--- a/src/indexer/log_merge_policy.rs
+++ b/src/indexer/log_merge_policy.rs
@@ -58,7 +58,7 @@ impl MergePolicy for LogMergePolicy {
             .enumerate()
             .collect::<Vec<(usize, u32)>>();
 
-        size_sorted_tuples.sort_by(|x, y| y.cmp(x));
+        size_sorted_tuples.sort_by(|x, y| y.1.cmp(&(x.1)));
 
         let size_sorted_log_tuples: Vec<_> = size_sorted_tuples
             .into_iter()
@@ -134,12 +134,21 @@ mod tests {
     #[test]
     fn test_log_merge_policy_levels() {
         // multiple levels all get merged correctly
+        // 2 MergeCandidates expected:
+        // * one with the 6 * 10-docs segments
+        // * one with the 3 * 1000-docs segments
+        // no MergeCandidate expected for the 2 * 10_000-docs segments as min_merge_size=3
         let test_input = vec![seg_meta(10),
                               seg_meta(10),
                               seg_meta(10),
                               seg_meta(1000),
                               seg_meta(1000),
-                              seg_meta(1000)];
+                              seg_meta(1000),
+                              seg_meta(10000),
+                              seg_meta(10000),
+                              seg_meta(10),
+                              seg_meta(10),
+                              seg_meta(10)];
         let result_list = test_merge_policy().compute_merge_candidates(&test_input);
         assert_eq!(result_list.len(), 2);
     }
@@ -147,18 +156,18 @@ mod tests {
     #[test]
     fn test_log_merge_policy_within_levels() {
         // multiple levels all get merged correctly
-        let test_input = vec![seg_meta(10),
-                              seg_meta(11),
-                              seg_meta(12),
-                              seg_meta(1000),
-                              seg_meta(1000),
-                              seg_meta(1000)];
+        let test_input = vec![seg_meta(10), // log2(10) = ~3.32 (> 3.58 - 0.75)
+                              seg_meta(11), // log2(11) = ~3.46
+                              seg_meta(12), // log2(12) = ~3.58
+                              seg_meta(800),  // log2(800) = ~9.64 (> 9.97 - 0.75)
+                              seg_meta(1000),  // log2(1000) = ~9.97
+                              seg_meta(1000)]; // log2(1000) = ~9.97
         let result_list = test_merge_policy().compute_merge_candidates(&test_input);
         assert_eq!(result_list.len(), 2);
     }
     #[test]
     fn test_log_merge_policy_small_segments() {
-        // multiple levels all get merged correctly
+        // segments under min_layer_size are merged together
         let test_input = vec![seg_meta(1),
                               seg_meta(1),
                               seg_meta(1),