Merge pull request #63854 from ClickHouse/backport/24.4/63753

Backport #63753 to 24.4: Allow cast from Array(Nothing) to Map(Nothing, Nothing)

src/Functions/FunctionsConversion.cpp

@@ -7,6 +7,7 @@
 #include <Columns/ColumnFixedString.h>
 #include <Columns/ColumnLowCardinality.h>
 #include <Columns/ColumnMap.h>
+#include <Columns/ColumnNothing.h>
 #include <Columns/ColumnNullable.h>
 #include <Columns/ColumnObject.h>
 #include <Columns/ColumnString.h>
@@ -3771,6 +3772,12 @@ class FunctionCast final : public IFunctionBase
         }
         else if (const auto * from_array = typeid_cast<const DataTypeArray *>(from_type_untyped.get()))
         {
+            if (typeid_cast<const DataTypeNothing *>(from_array->getNestedType().get()))
+                return [nested = to_type->getNestedType()](ColumnsWithTypeAndName &, const DataTypePtr &, const ColumnNullable *, size_t size)
+                {
+                    return ColumnMap::create(nested->createColumnConstWithDefaultValue(size)->convertToFullColumnIfConst());
+                };
+
             const auto * nested_tuple = typeid_cast<const DataTypeTuple *>(from_array->getNestedType().get());
             if (!nested_tuple || nested_tuple->getElements().size() != 2)
                 throw Exception(

tests/queries/0_stateless/01787_map_remote.reference

@@ -2,3 +2,6 @@
 {'a':1,'b':2}
 {'a':1,'b':2}
 {'a':1,'b':2}
+{}
+{}
+{'':''}

tests/queries/0_stateless/01787_map_remote.sql

@@ -1,2 +1,8 @@
 SELECT map('a', 1, 'b', 2) FROM remote('127.0.0.{1,2}', system, one);
 SELECT map('a', 1, 'b', 2) FROM remote('127.0.0.{1,2}');
+
+SELECT map() from remote('127.0.0.{1,2}', system,one);
+
+drop table if exists bug_repro_local;
+CREATE TABLE bug_repro_local (`attributes` Map(LowCardinality(String), String)) ENGINE = Log as select map('','');
+SELECT if(1, attributes, map()) from remote('127.0.0.{1,2}', currentDatabase(), bug_repro_local) limit 1;