add debug prints in hashjoin

Author: karthikeyann

velox/experimental/cudf/exec/CudfHashJoin.cpp

@@ -18,6 +18,7 @@
 #include "velox/experimental/cudf/exec/ExpressionEvaluator.h"
 #include "velox/experimental/cudf/exec/ToCudf.h"
 #include "velox/experimental/cudf/exec/Utilities.h"
+#include "velox/experimental/cudf/exec/VeloxCudfInterop.h"
 
 #include "velox/exec/Task.h"
 
@@ -407,6 +408,25 @@ RowVectorPtr CudfHashJoinProbe::getOutput() {
   auto leftTableView = leftTable->view();
   auto rightTableView = rightTable->view();
 
+  // add env variable to print the table
+  if (std::getenv("PRINT_TABLE") != nullptr && std::string(std::getenv("PRINT_TABLE")) == "1") {
+    // debug print leftTable
+    auto leftTableVelox = facebook::velox::cudf_velox::with_arrow::toVeloxColumn(leftTableView, pool(), "", stream);
+    std::cout << "Left table: " << std::endl << leftTableVelox->toString();
+  for (int i = 0; i < leftTableVelox->size(); i++) {
+    std::cout << leftTableVelox->toString(i) << std::endl;
+  }
+  std::cout << std::endl << "--------------------------------" << std::endl;
+  // debug print rightTable
+  auto rightTableVelox = facebook::velox::cudf_velox::with_arrow::toVeloxColumn(rightTableView, pool(), "", stream);
+  std::cout << "Right table: " << std::endl << rightTableVelox->toString();
+  for (int i = 0; i < rightTableVelox->size(); i++) {
+    std::cout << rightTableVelox->toString(i) << std::endl;
+  }
+  }
+
+  std::cout << std::endl << "--------------------------------" << std::endl;
+
   if (joinNode_->isInnerJoin()) {
     // left = probe, right = build
     if (joinNode_->filter()) {
@@ -519,6 +539,9 @@ RowVectorPtr CudfHashJoinProbe::getOutput() {
   } else {
     VELOX_FAIL("Unsupported join type: ", joinNode_->joinType());
   }
+  // print info about leftJoinIndices and rightJoinIndices
+  std::cout << "Left join indices: " << leftJoinIndices->size() << std::endl;
+  std::cout << "Right join indices: " << rightJoinIndices->size() << std::endl;
   auto leftIndicesSpan = leftJoinIndices
       ? cudf::device_span<cudf::size_type const>{*leftJoinIndices}
       : cudf::device_span<cudf::size_type const>{};