Fix segfault in Avro with LowCardinality(Nullable)

src/Processors/Formats/Impl/AvroRowInputFormat.cpp

@@ -35,6 +35,7 @@
 #include <Columns/ColumnNullable.h>
 #include <Columns/ColumnString.h>
 #include <Columns/ColumnsNumber.h>
+#include <Columns/ColumnLowCardinality.h>
 
 #include <avro/Compiler.hh>
 #include <avro/DataFile.hh>
@@ -178,7 +179,20 @@ static std::string nodeName(avro::NodePtr node)
 
 AvroDeserializer::DeserializeFn AvroDeserializer::createDeserializeFn(avro::NodePtr root_node, DataTypePtr target_type)
 {
-    const WhichDataType target = removeLowCardinality(target_type);
+    if (target_type->lowCardinality())
+    {
+        const auto * lc_type = assert_cast<const DataTypeLowCardinality *>(target_type.get());
+        auto dict_deserialize = createDeserializeFn(root_node, lc_type->getDictionaryType());
+        return [dict_deserialize](IColumn & column, avro::Decoder & decoder)
+        {
+            auto & lc_column = assert_cast<ColumnLowCardinality &>(column);
+            auto tmp_column = lc_column.getDictionary().getNestedColumn()->cloneEmpty();
+            dict_deserialize(*tmp_column, decoder);
+            lc_column.insertFromFullColumn(*tmp_column, 0);
+        };
+    }
+
+    const WhichDataType target = WhichDataType(target_type);
 
     switch (root_node->type())
     {

tests/queries/0_stateless/01543_avro_deserialization_with_lc.reference

@@ -0,0 +1,30 @@
+0	0
+1	1
+2	2
+3	3
+4	4
+5	5
+6	6
+7	7
+8	8
+9	9
+0	0
+1	1
+2	2
+3	3
+4	4
+5	5
+6	6
+7	7
+8	8
+9	9
+\N
+1
+\N
+3
+\N
+5
+\N
+7
+\N
+9

tests/queries/0_stateless/01543_avro_deserialization_with_lc.sh

@@ -1,14 +1,28 @@
 #!/usr/bin/env bash
-# Tags: no-unbundled, no-fasttest
+# Tags: no-unbundled, no-fasttest, no-parallel
 
 CURDIR=$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)
 # shellcheck source=../shell_config.sh
 . "$CURDIR"/../shell_config.sh
 
-$CLICKHOUSE_CLIENT --query "CREATE TABLE IF NOT EXISTS test_01543 (value LowCardinality(String)) ENGINE=Memory()"
-$CLICKHOUSE_CLIENT --query "INSERT INTO test_01543 SELECT toString(number) FROM numbers(1000)"
+USER_FILES_PATH=$(clickhouse-client --query "select _path,_file from file('nonexist.txt', 'CSV', 'val1 char')" 2>&1 | grep Exception | awk '{gsub("/nonexist.txt","",$9); print $9}')
+
+$CLICKHOUSE_CLIENT --multiquery --query "
+SET allow_suspicious_low_cardinality_types=1;
+CREATE TABLE IF NOT EXISTS test_01543 (value LowCardinality(String), value2 LowCardinality(UInt64)) ENGINE=Memory();
+"
+
+$CLICKHOUSE_CLIENT --query "INSERT INTO test_01543 SELECT toString(number), number FROM numbers(10)"
 
 $CLICKHOUSE_CLIENT -q "SELECT * FROM test_01543 FORMAT Avro" |
     $CLICKHOUSE_CLIENT -q "INSERT INTO test_01543 FORMAT Avro";
 
+$CLICKHOUSE_CLIENT -q "SELECT * FROM test_01543";
+
 $CLICKHOUSE_CLIENT --query "DROP TABLE IF EXISTS test_01543"
+
+$CLICKHOUSE_CLIENT --query "SELECT number % 2 ? number: NULL as x from numbers(10) FORMAT Avro" > $USER_FILES_PATH/test_01543.avro
+
+$CLICKHOUSE_CLIENT --query "SELECT * FROM file('test_01543.avro', 'Avro', 'x LowCardinality(Nullable(UInt64))')"
+
+rm $USER_FILES_PATH/test_01543.avro