Merge pull request #16010 from ClickHouse/backport/20.7/15662

Backport #15662 to 20.7: Fix read from Buffer table with empty nested table with different types.
ClickHouse · Oct 16, 2020 · e290b17 · e290b17
2 parents 343dcd2 + 631adde
commit e290b17
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Showing 3 changed files with 22 additions and 6 deletions.
diff --git a/src/Storages/StorageBuffer.cpp b/src/Storages/StorageBuffer.cpp
@@ -221,13 +221,16 @@ Pipes StorageBuffer::read(
                     columns_intersection, destination_metadata_snapshot, query_info,
                     context, processed_stage, max_block_size, num_streams);
 
-                for (auto & pipe : pipes_from_dst)
+                if (!pipes_from_dst.empty())
                 {
-                    pipe.addSimpleTransform(std::make_shared<AddingMissedTransform>(
-                            pipe.getHeader(), header_after_adding_defaults, metadata_snapshot->getColumns(), context));
-
-                    pipe.addSimpleTransform(std::make_shared<ConvertingTransform>(
-                            pipe.getHeader(), header, ConvertingTransform::MatchColumnsMode::Name));
+                    for (auto & pipe : pipes_from_dst)
+                    {
+                        pipe.addSimpleTransform(std::make_shared<AddingMissedTransform>(
+                                pipe.getHeader(), header_after_adding_defaults, metadata_snapshot->getColumns(), context));
+
+                        pipe.addSimpleTransform(std::make_shared<ConvertingTransform>(
+                                pipe.getHeader(), header, ConvertingTransform::MatchColumnsMode::Name));
+                    }
                 }
             }
         }

diff --git a/tests/queries/0_stateless/01514_empty_buffer_different_types.reference b/tests/queries/0_stateless/01514_empty_buffer_different_types.reference
@@ -0,0 +1 @@
+a
diff --git a/tests/queries/0_stateless/01514_empty_buffer_different_types.sql b/tests/queries/0_stateless/01514_empty_buffer_different_types.sql
@@ -0,0 +1,12 @@
+set send_logs_level = 'error';
+
+DROP TABLE IF EXISTS merge_tree_table1;
+CREATE TABLE merge_tree_table1 (`s` LowCardinality(String), x UInt32) ENGINE = MergeTree ORDER BY x settings index_granularity = 1;
+CREATE TABLE buffer_table1 ( `s` String , x UInt32) ENGINE = Buffer(currentDatabase(), 'merge_tree_table1', 16, 10, 60, 10, 1000, 1048576, 2097152);
+SELECT s FROM buffer_table1;
+
+insert into merge_tree_table1 values ('a', 1);
+select s from buffer_table1 where x = 1;
+select s from buffer_table1 where x = 2;
+
+DROP TABLE IF EXISTS merge_tree_table1;