Fix ClickHouse-sourced dictionaries with an explicit query

src/Dictionaries/ExternalQueryBuilder.cpp

@@ -396,18 +396,20 @@ std::string ExternalQueryBuilder::composeLoadKeysQuery(
     }
     else
     {
-        writeString(query, out);
-
         auto condition_position = query.find(CONDITION_PLACEHOLDER_TO_REPLACE_VALUE);
         if (condition_position == std::string::npos)
         {
-            writeString(" WHERE ", out);
+            writeString("SELECT * FROM (", out);
+            writeString(query, out);
+            writeString(") WHERE ", out);
             composeKeysCondition(key_columns, requested_rows, method, partition_key_prefix, out);
             writeString(";", out);
 
             return out.str();
         }
 
+        writeString(query, out);
+
         WriteBufferFromOwnString condition_value_buffer;
         composeKeysCondition(key_columns, requested_rows, method, partition_key_prefix, condition_value_buffer);
         const auto & condition_value = condition_value_buffer.str();

tests/queries/0_stateless/02907_clickhouse_dictionary_bug.reference

@@ -0,0 +1 @@
+b

tests/queries/0_stateless/02907_clickhouse_dictionary_bug.sh

@@ -0,0 +1,20 @@
+#!/usr/bin/env bash
+# Tags: zookeeper
+
+CURDIR=$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)
+# shellcheck source=../shell_config.sh
+. "$CURDIR"/../shell_config.sh
+
+${CLICKHOUSE_CLIENT} -n -q "
+    DROP DICTIONARY IF EXISTS 02907_dictionary;
+    DROP TABLE IF EXISTS 02907_table;
+
+    CREATE TABLE 02907_table (A String, B String) ENGINE=Memory AS SELECT 'a', 'b';
+    CREATE DICTIONARY 02907_dictionary(A String, B String) PRIMARY KEY A
+    SOURCE(CLICKHOUSE(QUERY \$\$  SELECT A, B FROM ${CLICKHOUSE_DATABASE}.02907_table ORDER BY A DESC LIMIT 1 BY A  \$\$))
+    LAYOUT(complex_key_direct());
+
+    SELECT dictGet('02907_dictionary','B','a');
+
+    DROP DICTIONARY 02907_dictionary;
+    DROP TABLE 02907_table;"