From 9bf50ac814f59a1936dbe1b64a717718af1cfea8 Mon Sep 17 00:00:00 2001
From: Antonio Andelic <antonio@clickhouse.com>
Date: Wed, 20 Mar 2024 14:50:26 +0100
Subject: [PATCH] Fix aggregator when data is empty

---
 src/Interpreters/Aggregator.cpp                            | 7 ++++++-
 .../03015_aggregator_empty_data_multiple_blocks.reference  | 0
 .../03015_aggregator_empty_data_multiple_blocks.sql        | 3 +++
 3 files changed, 9 insertions(+), 1 deletion(-)
 create mode 100644 tests/queries/0_stateless/03015_aggregator_empty_data_multiple_blocks.reference
 create mode 100644 tests/queries/0_stateless/03015_aggregator_empty_data_multiple_blocks.sql

diff --git a/src/Interpreters/Aggregator.cpp b/src/Interpreters/Aggregator.cpp
index 1c0d4b2d671..7f3b961a598 100644
--- a/src/Interpreters/Aggregator.cpp
+++ b/src/Interpreters/Aggregator.cpp
@@ -1867,7 +1867,12 @@ Aggregator::convertToBlockImpl(Method & method, Table & data, Arena * arena, Are
     if (data.empty())
     {
         auto && out_cols = prepareOutputBlockColumns(params, aggregate_functions, getHeader(final), aggregates_pools, final, rows);
-        return {finalizeBlock(params, getHeader(final), std::move(out_cols), final, rows)};
+        auto finalized_block = finalizeBlock(params, getHeader(final), std::move(out_cols), final, rows);
+
+        if (return_single_block)
+            return std::move(finalized_block);
+
+        return BlocksList{std::move(finalized_block)};
     }
     ConvertToBlockResVariant res;
     bool use_compiled_functions = false;
diff --git a/tests/queries/0_stateless/03015_aggregator_empty_data_multiple_blocks.reference b/tests/queries/0_stateless/03015_aggregator_empty_data_multiple_blocks.reference
new file mode 100644
index 00000000000..e69de29bb2d
diff --git a/tests/queries/0_stateless/03015_aggregator_empty_data_multiple_blocks.sql b/tests/queries/0_stateless/03015_aggregator_empty_data_multiple_blocks.sql
new file mode 100644
index 00000000000..d2c1816f7e8
--- /dev/null
+++ b/tests/queries/0_stateless/03015_aggregator_empty_data_multiple_blocks.sql
@@ -0,0 +1,3 @@
+CREATE TABLE 03015_aggregator_empty_data_multiple_blocks (c0 Int32) ENGINE = Memory();
+INSERT INTO 03015_aggregator_empty_data_multiple_blocks SELECT * FROM generateRandom() LIMIT 1000;
+SELECT radians(t1.c0) FROM 03015_aggregator_empty_data_multiple_blocks AS t1 RIGHT ANTI JOIN 03015_aggregator_empty_data_multiple_blocks AS right_0 ON t1.c0=right_0.c0 GROUP BY t1.c0;