From 652d04e78a96d6dc71ef913dd2dcf253597d8c40 Mon Sep 17 00:00:00 2001
From: Tomasz Grabiec <tgrabiec@scylladb.com>
Date: Fri, 7 Apr 2017 10:23:26 +0200
Subject: [PATCH] clustering_ranges_walker: Generalize to work on position
 ranges

It will include the static row by default. This will allow simplifying
users, which work with position ranges already.
---
 clustering_ranges_walker.hh | 74 ++++++++++++++++++++++---------------
 1 file changed, 44 insertions(+), 30 deletions(-)

diff --git a/clustering_ranges_walker.hh b/clustering_ranges_walker.hh
index bf15dee157..05e6c756ab 100644
--- a/clustering_ranges_walker.hh
+++ b/clustering_ranges_walker.hh
@@ -27,19 +27,38 @@
 #include "query-request.hh"
 #include "streamed_mutation.hh"
 
-// Utility for in-order checking of overlap with clustering ranges.
+// Utility for in-order checking of overlap with position ranges.
+// Always includes the static row initially.
 class clustering_ranges_walker {
     const schema& _schema;
     const query::clustering_row_ranges& _ranges;
     query::clustering_row_ranges::const_iterator _current;
     query::clustering_row_ranges::const_iterator _end;
-    bool _in_current = false;
+    bool _in_current; // next position is known to be >= _current_start
+    position_in_partition_view _current_start;
+    position_in_partition_view _current_end;
+private:
+    bool advance_to_next_range() {
+        _in_current = false;
+        if (!_current_start.is_static_row()) {
+            ++_current;
+        }
+        if (_current == _end) {
+            return false;
+        }
+        _current_start = position_in_partition_view::for_range_start(*_current);
+        _current_end = position_in_partition_view::for_range_end(*_current);
+        return true;
+    }
 public:
     clustering_ranges_walker(const schema& s, const query::clustering_row_ranges& ranges)
         : _schema(s)
         , _ranges(ranges)
         , _current(ranges.begin())
         , _end(ranges.end())
+        , _in_current(true)
+        , _current_start(position_in_partition_view::for_static_row())
+        , _current_end(position_in_partition_view::before_all_clustered_rows())
     { }
     clustering_ranges_walker(clustering_ranges_walker&& o) noexcept
         : _schema(o._schema)
@@ -47,6 +66,8 @@ public:
         , _current(o._current)
         , _end(o._end)
         , _in_current(o._in_current)
+        , _current_start(o._current_start)
+        , _current_end(o._current_end)
     { }
     clustering_ranges_walker& operator=(clustering_ranges_walker&& o) {
         if (this != &o) {
@@ -62,29 +83,22 @@ public:
     bool advance_to(position_in_partition_view pos) {
         position_in_partition::less_compare less(_schema);
 
-        while (_current != _end) {
-            if (!_in_current && _current->start()) {
-                auto range_start = position_in_partition_view::for_range_start(*_current);
-                if (less(pos, range_start)) {
-                    return false;
-                }
+        if (_current == _end) {
+            return false;
+        }
+
+        do {
+            if (!_in_current && less(pos, _current_start)) {
+                break;
             }
             // All subsequent clustering keys are larger than the start of this
             // range so there is no need to check that again.
             _in_current = true;
 
-            if (!_current->end()) {
+            if (less(pos, _current_end)) {
                 return true;
             }
-
-            auto range_end = position_in_partition_view::for_range_end(*_current);
-            if (less(pos, range_end)) {
-                return true;
-            }
-
-            ++_current;
-            _in_current = false;
-        }
+        } while (advance_to_next_range());
 
         return false;
     }
@@ -97,20 +111,18 @@ public:
     bool advance_to(position_in_partition_view start, position_in_partition_view end) {
         position_in_partition::less_compare less(_schema);
 
-        while (_current != _end) {
-            position_in_partition_view range_start(position_in_partition_view::range_tag_t(), bound_view::from_range_start(*_current));
-            if (less(end, range_start)) {
-                return false;
-            }
+        if (_current == _end) {
+            return false;
+        }
 
-            position_in_partition_view range_end(position_in_partition_view::range_tag_t(), bound_view::from_range_end(*_current));
-            if (less(start, range_end)) {
+        do {
+            if (less(end, _current_start)) {
+                break;
+            }
+            if (less(start, _current_end)) {
                 return true;
             }
-
-            ++_current;
-            _in_current = false;
-        }
+        } while (advance_to_next_range());
 
         return false;
     }
@@ -123,6 +135,8 @@ public:
     // Resets the state of the walker so that advance_to() can be now called for new sequence of positions.
     void reset() {
         _current = _ranges.begin();
-        _in_current = false;
+        _current_start = position_in_partition_view::for_static_row();
+        _current_end = position_in_partition_view::before_all_clustered_rows();
+        _in_current = true;
     }
 };