Backport #95072 to 25.12: Fix crash in getTopKMarks when limit is zero

robot-clickhouse · robot-clickhouse · commit 384dc5260f10 · 2026-01-25T17:12:27.000Z
diff --git a/src/Storages/MergeTree/MergeTreeIndexMinMax.cpp b/src/Storages/MergeTree/MergeTreeIndexMinMax.cpp
@@ -267,6 +267,9 @@ void MergeTreeIndexBulkGranulesMinMax::deserializeBinary(size_t granule_num, Rea
 
 void MergeTreeIndexBulkGranulesMinMax::getTopKMarks(size_t n, std::vector<MinMaxGranule> & result)
 {
+    if (n == 0)
+        return;
+
     if (n >= granules.size())
     {
         result.insert(result.end(), granules.begin(), granules.end());
@@ -301,6 +304,9 @@ void MergeTreeIndexBulkGranulesMinMax::getTopKMarks(int direction,
                                                     const std::vector<std::vector<MinMaxGranule>> & parts,
                                                     std::vector<MarkRanges> & result)
 {
+    if (n == 0)
+        return;
+
     std::priority_queue<MinMaxGranuleItem> queue;
 
     for (size_t part_index = 0; part_index < parts.size(); ++part_index)
diff --git a/tests/queries/0_stateless/03807_top_k_limit_zero.reference b/tests/queries/0_stateless/03807_top_k_limit_zero.reference
diff --git a/tests/queries/0_stateless/03807_top_k_limit_zero.sql b/tests/queries/0_stateless/03807_top_k_limit_zero.sql
@@ -0,0 +1,18 @@
+-- Test for crash when LIMIT 0 is used with use_skip_indexes_for_top_k
+-- Regression test for https://github.com/ClickHouse/ClickHouse/issues/95065
+
+DROP TABLE IF EXISTS tab;
+
+CREATE TABLE tab
+(
+    id UInt32,
+    v1 UInt32,
+    INDEX v1idx v1 TYPE minmax GRANULARITY 1
+) Engine = MergeTree ORDER BY id SETTINGS index_granularity = 64;
+
+INSERT INTO tab SELECT number, number FROM numbers(1000);
+
+SELECT id, v1 FROM tab ORDER BY v1 DESC NULLS LAST LIMIT 0 SETTINGS use_skip_indexes_for_top_k = 1;
+SELECT id, v1 FROM tab ORDER BY v1 ASC LIMIT 0 SETTINGS use_skip_indexes_for_top_k = 1;
+
+DROP TABLE tab;

Original file line number	Diff line number	Diff line change
`@@ -267,6 +267,9 @@ void MergeTreeIndexBulkGranulesMinMax::deserializeBinary(size_t granule_num, Rea`
`267`	`267`
`268`	`268`	`void MergeTreeIndexBulkGranulesMinMax::getTopKMarks(size_t n, std::vector<MinMaxGranule> & result)`
`269`	`269`	`{`
	`270`	`+ if (n == 0)`
	`271`	`+ return;`
	`272`	`+`
`270`	`273`	`if (n >= granules.size())`
`271`	`274`	`{`
`272`	`275`	`result.insert(result.end(), granules.begin(), granules.end());`
`@@ -301,6 +304,9 @@ void MergeTreeIndexBulkGranulesMinMax::getTopKMarks(int direction,`
`301`	`304`	`const std::vector<std::vector<MinMaxGranule>> & parts,`
`302`	`305`	`std::vector<MarkRanges> & result)`
`303`	`306`	`{`
	`307`	`+ if (n == 0)`
	`308`	`+ return;`
	`309`	`+`
`304`	`310`	`std::priority_queue<MinMaxGranuleItem> queue;`
`305`	`311`
`306`	`312`	`for (size_t part_index = 0; part_index < parts.size(); ++part_index)`