fix(fuzzer): Fix toSql methods for NestedLoopJoinNode in Reference Qu…

…ery Runners (facebookincubator#11576)

Summary:

The select clause is completely missing in the produced query string.

Reviewed By: kagamiori

Differential Revision: D66132514

velox/exec/fuzzer/DuckQueryRunner.cpp

@@ -445,20 +445,11 @@ std::optional<std::string> DuckQueryRunner::toSql(
 
 std::optional<std::string> DuckQueryRunner::toSql(
     const std::shared_ptr<const core::NestedLoopJoinNode>& joinNode) {
-  const auto& joinKeysToSql = [](auto keys) {
-    std::stringstream out;
-    for (auto i = 0; i < keys.size(); ++i) {
-      if (i > 0) {
-        out << ", ";
-      }
-      out << keys[i]->name();
-    }
-    return out.str();
-  };
-
   const auto& outputNames = joinNode->outputType()->names();
   std::stringstream sql;
 
+  sql << "SELECT " << folly::join(", ", outputNames);
+
   // Nested loop join without filter.
   VELOX_CHECK(
       joinNode->joinCondition() == nullptr,

velox/exec/fuzzer/PrestoQueryRunner.cpp

@@ -659,20 +659,11 @@ std::optional<std::string> PrestoQueryRunner::toSql(
 
 std::optional<std::string> PrestoQueryRunner::toSql(
     const std::shared_ptr<const core::NestedLoopJoinNode>& joinNode) {
-  const auto& joinKeysToSql = [](auto keys) {
-    std::stringstream out;
-    for (auto i = 0; i < keys.size(); ++i) {
-      if (i > 0) {
-        out << ", ";
-      }
-      out << keys[i]->name();
-    }
-    return out.str();
-  };
-
   const auto& outputNames = joinNode->outputType()->names();
   std::stringstream sql;
 
+  sql << "SELECT " << folly::join(", ", outputNames);
+
   // Nested loop join without filter.
   VELOX_CHECK(
       joinNode->joinCondition() == nullptr,