From aeffbb6732f9a55434e0772e04d79f207b1cb74d Mon Sep 17 00:00:00 2001
From: Avi Kivity <avi@scylladb.com>
Date: Wed, 13 Jun 2018 16:15:47 +0300
Subject: [PATCH] database: stop using incremental selectors

There is a bug in incremental_selector for partitioned_sstable_set, so
until it is found, stop using it.

This degrades scan performance of Leveled Compaction Strategy tables.

Fixes #3513. (as a workaround)
Introduced: 2.1
Message-Id: <20180613131547.19084-1-avi@scylladb.com>
---
 database.cc | 26 ++++++++++++++++----------
 1 file changed, 16 insertions(+), 10 deletions(-)

diff --git a/database.cc b/database.cc
index 9209f7d755..14a9107bae 100644
--- a/database.cc
+++ b/database.cc
@@ -4597,11 +4597,14 @@ flat_mutation_reader make_local_shard_sstable_reader(schema_ptr s,
         }
         return reader;
     };
-    return make_combined_reader(s, std::make_unique<incremental_reader_selector>(s,
-                    std::move(sstables),
-                    pr,
-                    std::move(trace_state),
-                    std::move(reader_factory_fn)),
+    auto all_readers = boost::copy_range<std::vector<flat_mutation_reader>>(
+            *sstables->all()
+            | boost::adaptors::transformed([&] (sstables::shared_sstable sst) -> flat_mutation_reader {
+                return reader_factory_fn(sst, pr);
+            })
+    );
+    return make_combined_reader(s,
+            std::move(all_readers),
             fwd,
             fwd_mr);
 }
@@ -4620,11 +4623,14 @@ flat_mutation_reader make_range_sstable_reader(schema_ptr s,
     auto reader_factory_fn = [s, &slice, &pc, resource_tracker, fwd, fwd_mr, &monitor_generator] (sstables::shared_sstable& sst, const dht::partition_range& pr) {
         return sst->read_range_rows_flat(s, pr, slice, pc, resource_tracker, fwd, fwd_mr, monitor_generator(sst));
     };
-    return make_combined_reader(s, std::make_unique<incremental_reader_selector>(s,
-                    std::move(sstables),
-                    pr,
-                    std::move(trace_state),
-                    std::move(reader_factory_fn)),
+    auto sstable_readers = boost::copy_range<std::vector<flat_mutation_reader>>(
+            *sstables->all()
+            | boost::adaptors::transformed([&] (sstables::shared_sstable sst) {
+                return reader_factory_fn(sst, pr);
+            })
+    );
+    return make_combined_reader(s,
+            std::move(sstable_readers),
             fwd,
             fwd_mr);
 }