Refactoring

Author: lalinsky

src/Index.zig

@@ -136,11 +136,11 @@ fn prepareMemorySegmentMerge(self: *Self) !?MemorySegmentList.PreparedMerge {
     self.segments_lock.lockShared();
     defer self.segments_lock.unlockShared();
 
-    const merge = try self.memory_segments.prepareMerge() orelse return null;
+    var merge = try self.memory_segments.prepareMerge() orelse return null;
+    defer merge.merger.deinit();
     errdefer self.memory_segments.destroySegment(merge.target);
 
-    std.debug.assert(merge.sources.num_segments == 2);
-    try merge.target.data.merge(&merge.sources.start.data, &merge.sources.end.data, &self.memory_segments);
+    try merge.target.data.merge(&merge.merger);
 
     return merge;
 }
@@ -410,21 +410,11 @@ fn prepareFileSegmentMerge(self: *Self) !?FileSegmentList.PreparedMerge {
     self.segments_lock.lockShared();
     defer self.segments_lock.unlockShared();
 
-    const merge = try self.file_segments.prepareMerge() orelse return null;
+    var merge = try self.file_segments.prepareMerge() orelse return null;
+    defer merge.merger.deinit();
     errdefer self.file_segments.destroySegment(merge.target);
 
-    var merger = SegmentMerger(FileSegment).init(self.allocator, &self.file_segments);
-    defer merger.deinit();
-
-    var source_node = merge.sources.start;
-    while (true) {
-        try merger.addSource(&source_node.data);
-        if (source_node == merge.sources.end) break;
-        source_node = source_node.next orelse break;
-    }
-    try merger.prepare();
-
-    try merge.target.data.build(self.data_dir, &merger);
+    try merge.target.data.build(self.data_dir, &merge.merger);
 
     return merge;
 }

src/MemorySegment.zig

@@ -101,14 +101,7 @@ pub fn build(self: *Self, changes: []const Change) !void {
     std.sort.pdq(Item, self.items.items, {}, Item.cmp);
 }
 
-pub fn merge(self: *Self, source1: *Self, source2: *Self, collection: *List) !void {
-    var merger = SegmentMerger(Self).init(self.allocator, collection);
-    defer merger.deinit();
-
-    try merger.addSource(source1);
-    try merger.addSource(source2);
-    try merger.prepare();
-
+pub fn merge(self: *Self, merger: *SegmentMerger(Self)) !void {
     self.id = merger.segment.id;
     self.max_commit_id = merger.segment.max_commit_id;
 

src/segment_list.zig

@@ -3,6 +3,7 @@ const std = @import("std");
 const common = @import("common.zig");
 const SearchResults = common.SearchResults;
 
+const SegmentMerger = @import("segment_merger.zig").SegmentMerger;
 const TieredMergePolicy = @import("segment_merge_policy.zig").TieredMergePolicy;
 
 const Deadline = @import("utils/Deadline.zig");
@@ -106,12 +107,25 @@ pub fn SegmentList(Segment: type) type {
         pub const PreparedMerge = struct {
             sources: SegmentsToMerge,
             target: *List.Node,
+            merger: SegmentMerger(Segment),
         };
 
         pub fn prepareMerge(self: *Self) !?PreparedMerge {
             const sources = self.merge_policy.findSegmentsToMerge(self.segments) orelse return null;
+
+            var merger = SegmentMerger(Segment).init(self.allocator, self);
+            errdefer merger.deinit();
+
+            var source_node = sources.start;
+            while (true) {
+                try merger.addSource(&source_node.data);
+                if (source_node == sources.end) break;
+                source_node = source_node.next orelse break;
+            }
+            try merger.prepare();
+
             const target = try self.createSegment();
-            return .{ .sources = sources, .target = target };
+            return .{ .sources = sources, .merger = merger, .target = target };
         }
 
         pub fn applyMerge(self: *Self, merge: PreparedMerge) void {