From 132edc9e2217ae99e7936560779ff6b2daefa327 Mon Sep 17 00:00:00 2001
From: Alexey Milovidov <milovidov@yandex-team.ru>
Date: Fri, 2 Jul 2021 22:47:43 +0300
Subject: [PATCH] Allow quantiles* functions to work with
 `aggregate_functions_null_for_empty`

---
 .../AggregateFunctionQuantile.cpp             | 29 ++++++++++---------
 ...936_quantiles_cannot_return_null.reference |  4 +++
 .../01936_quantiles_cannot_return_null.sql    |  9 ++++++
 3 files changed, 29 insertions(+), 13 deletions(-)
 create mode 100644 tests/queries/0_stateless/01936_quantiles_cannot_return_null.reference
 create mode 100644 tests/queries/0_stateless/01936_quantiles_cannot_return_null.sql

diff --git a/src/AggregateFunctions/AggregateFunctionQuantile.cpp b/src/AggregateFunctions/AggregateFunctionQuantile.cpp
index cae0021082f..11b14585653 100644
--- a/src/AggregateFunctions/AggregateFunctionQuantile.cpp
+++ b/src/AggregateFunctions/AggregateFunctionQuantile.cpp
@@ -125,44 +125,47 @@ AggregateFunctionPtr createAggregateFunctionQuantile(
 
 void registerAggregateFunctionsQuantile(AggregateFunctionFactory & factory)
 {
+    /// For aggregate functions returning array we cannot return NULL on empty set.
+    AggregateFunctionProperties properties = { .returns_default_when_only_null = true };
+
     factory.registerFunction(NameQuantile::name, createAggregateFunctionQuantile<FuncQuantile>);
-    factory.registerFunction(NameQuantiles::name, createAggregateFunctionQuantile<FuncQuantiles>);
+    factory.registerFunction(NameQuantiles::name, { createAggregateFunctionQuantile<FuncQuantiles>, properties });
 
     factory.registerFunction(NameQuantileDeterministic::name, createAggregateFunctionQuantile<FuncQuantileDeterministic>);
-    factory.registerFunction(NameQuantilesDeterministic::name, createAggregateFunctionQuantile<FuncQuantilesDeterministic>);
+    factory.registerFunction(NameQuantilesDeterministic::name, { createAggregateFunctionQuantile<FuncQuantilesDeterministic>, properties });
 
     factory.registerFunction(NameQuantileExact::name, createAggregateFunctionQuantile<FuncQuantileExact>);
-    factory.registerFunction(NameQuantilesExact::name, createAggregateFunctionQuantile<FuncQuantilesExact>);
+    factory.registerFunction(NameQuantilesExact::name, { createAggregateFunctionQuantile<FuncQuantilesExact>, properties });
 
     factory.registerFunction(NameQuantileExactLow::name, createAggregateFunctionQuantile<FuncQuantileExactLow>);
-    factory.registerFunction(NameQuantilesExactLow::name, createAggregateFunctionQuantile<FuncQuantilesExactLow>);
+    factory.registerFunction(NameQuantilesExactLow::name, { createAggregateFunctionQuantile<FuncQuantilesExactLow>, properties });
 
     factory.registerFunction(NameQuantileExactHigh::name, createAggregateFunctionQuantile<FuncQuantileExactHigh>);
-    factory.registerFunction(NameQuantilesExactHigh::name, createAggregateFunctionQuantile<FuncQuantilesExactHigh>);
+    factory.registerFunction(NameQuantilesExactHigh::name, { createAggregateFunctionQuantile<FuncQuantilesExactHigh>, properties });
 
     factory.registerFunction(NameQuantileExactExclusive::name, createAggregateFunctionQuantile<FuncQuantileExactExclusive>);
-    factory.registerFunction(NameQuantilesExactExclusive::name, createAggregateFunctionQuantile<FuncQuantilesExactExclusive>);
+    factory.registerFunction(NameQuantilesExactExclusive::name, { createAggregateFunctionQuantile<FuncQuantilesExactExclusive>, properties });
 
     factory.registerFunction(NameQuantileExactInclusive::name, createAggregateFunctionQuantile<FuncQuantileExactInclusive>);
-    factory.registerFunction(NameQuantilesExactInclusive::name, createAggregateFunctionQuantile<FuncQuantilesExactInclusive>);
+    factory.registerFunction(NameQuantilesExactInclusive::name, { createAggregateFunctionQuantile<FuncQuantilesExactInclusive>, properties });
 
     factory.registerFunction(NameQuantileExactWeighted::name, createAggregateFunctionQuantile<FuncQuantileExactWeighted>);
-    factory.registerFunction(NameQuantilesExactWeighted::name, createAggregateFunctionQuantile<FuncQuantilesExactWeighted>);
+    factory.registerFunction(NameQuantilesExactWeighted::name, { createAggregateFunctionQuantile<FuncQuantilesExactWeighted>, properties });
 
     factory.registerFunction(NameQuantileTiming::name, createAggregateFunctionQuantile<FuncQuantileTiming>);
-    factory.registerFunction(NameQuantilesTiming::name, createAggregateFunctionQuantile<FuncQuantilesTiming>);
+    factory.registerFunction(NameQuantilesTiming::name, { createAggregateFunctionQuantile<FuncQuantilesTiming>, properties });
 
     factory.registerFunction(NameQuantileTimingWeighted::name, createAggregateFunctionQuantile<FuncQuantileTimingWeighted>);
-    factory.registerFunction(NameQuantilesTimingWeighted::name, createAggregateFunctionQuantile<FuncQuantilesTimingWeighted>);
+    factory.registerFunction(NameQuantilesTimingWeighted::name, { createAggregateFunctionQuantile<FuncQuantilesTimingWeighted>, properties });
 
     factory.registerFunction(NameQuantileTDigest::name, createAggregateFunctionQuantile<FuncQuantileTDigest>);
-    factory.registerFunction(NameQuantilesTDigest::name, createAggregateFunctionQuantile<FuncQuantilesTDigest>);
+    factory.registerFunction(NameQuantilesTDigest::name, { createAggregateFunctionQuantile<FuncQuantilesTDigest>, properties });
 
     factory.registerFunction(NameQuantileTDigestWeighted::name, createAggregateFunctionQuantile<FuncQuantileTDigestWeighted>);
-    factory.registerFunction(NameQuantilesTDigestWeighted::name, createAggregateFunctionQuantile<FuncQuantilesTDigestWeighted>);
+    factory.registerFunction(NameQuantilesTDigestWeighted::name, { createAggregateFunctionQuantile<FuncQuantilesTDigestWeighted>, properties });
 
     factory.registerFunction(NameQuantileBFloat16::name, createAggregateFunctionQuantile<FuncQuantileBFloat16>);
-    factory.registerFunction(NameQuantilesBFloat16::name, createAggregateFunctionQuantile<FuncQuantilesBFloat16>);
+    factory.registerFunction(NameQuantilesBFloat16::name, { createAggregateFunctionQuantile<FuncQuantilesBFloat16>, properties });
 
     /// 'median' is an alias for 'quantile'
     factory.registerAlias("median", NameQuantile::name);
diff --git a/tests/queries/0_stateless/01936_quantiles_cannot_return_null.reference b/tests/queries/0_stateless/01936_quantiles_cannot_return_null.reference
new file mode 100644
index 00000000000..f9b4a3157f7
--- /dev/null
+++ b/tests/queries/0_stateless/01936_quantiles_cannot_return_null.reference
@@ -0,0 +1,4 @@
+[nan]
+[nan]
+[nan]
+[nan]
diff --git a/tests/queries/0_stateless/01936_quantiles_cannot_return_null.sql b/tests/queries/0_stateless/01936_quantiles_cannot_return_null.sql
new file mode 100644
index 00000000000..81ac6224268
--- /dev/null
+++ b/tests/queries/0_stateless/01936_quantiles_cannot_return_null.sql
@@ -0,0 +1,9 @@
+set aggregate_functions_null_for_empty=0;
+
+SELECT quantiles(0.95)(x)　FROM　(SELECT 1 x WHERE 0);
+SELECT quantiles(0.95)(number)　FROM　(SELECT number FROM numbers(10) WHERE number > 10);
+
+set aggregate_functions_null_for_empty=1;
+
+SELECT quantiles(0.95)(x)　FROM　(SELECT 1 x WHERE 0);
+SELECT quantiles(0.95)(number)　FROM　(SELECT number FROM numbers(10) WHERE number > 10);