Broadcast Nested Loop Join - Left Anti and Left Semi (#159)

This PR is the first of two parts towards making TPC-H 16 work: the other will be implementing `is_distinct` for aggregate operations.

`BroadcastNestedLoopJoin` is Spark's "catch all" for non-equi joins. It works by first picking a side to broadcast, then iterating through every possible row combination and checking the non-equi condition against the pair.

src/enclave/App/App.cpp

@@ -555,6 +555,50 @@ Java_edu_berkeley_cs_rise_opaque_execution_SGXEnclave_NonObliviousSortMergeJoin(
   return ret;
 }
 
+JNIEXPORT jbyteArray JNICALL
+Java_edu_berkeley_cs_rise_opaque_execution_SGXEnclave_BroadcastNestedLoopJoin(
+  JNIEnv *env, jobject obj, jlong eid, jbyteArray join_expr, jbyteArray outer_rows, jbyteArray inner_rows) {
+  (void)obj;
+
+  jboolean if_copy;
+
+  uint32_t join_expr_length = (uint32_t) env->GetArrayLength(join_expr);
+  uint8_t *join_expr_ptr = (uint8_t *) env->GetByteArrayElements(join_expr, &if_copy);
+
+  uint32_t outer_rows_length = (uint32_t) env->GetArrayLength(outer_rows);
+  uint8_t *outer_rows_ptr = (uint8_t *) env->GetByteArrayElements(outer_rows, &if_copy);
+
+  uint32_t inner_rows_length = (uint32_t) env->GetArrayLength(inner_rows);
+  uint8_t *inner_rows_ptr = (uint8_t *) env->GetByteArrayElements(inner_rows, &if_copy);
+
+  uint8_t *output_rows = nullptr;
+  size_t output_rows_length = 0;
+
+  if (outer_rows_ptr == nullptr) {
+    ocall_throw("BroadcastNestedLoopJoin: JNI failed to get inner byte array.");
+  } else if (inner_rows_ptr == nullptr) {
+    ocall_throw("BroadcastNestedLoopJoin: JNI failed to get outer byte array.");
+  } else {
+    oe_check_and_time("Broadcast Nested Loop Join",
+                       ecall_broadcast_nested_loop_join(
+                         (oe_enclave_t*)eid,
+                         join_expr_ptr, join_expr_length,
+                         outer_rows_ptr, outer_rows_length,
+                         inner_rows_ptr, inner_rows_length,
+                         &output_rows, &output_rows_length));
+  }
+
+  jbyteArray ret = env->NewByteArray(output_rows_length);
+  env->SetByteArrayRegion(ret, 0, output_rows_length, (jbyte *) output_rows);
+  free(output_rows);
+
+  env->ReleaseByteArrayElements(join_expr, (jbyte *) join_expr_ptr, 0);
+  env->ReleaseByteArrayElements(outer_rows, (jbyte *) outer_rows_ptr, 0);
+  env->ReleaseByteArrayElements(inner_rows, (jbyte *) inner_rows_ptr, 0);
+
+  return ret;
+}
+
 JNIEXPORT jobject JNICALL
 Java_edu_berkeley_cs_rise_opaque_execution_SGXEnclave_NonObliviousAggregate(
   JNIEnv *env, jobject obj, jlong eid, jbyteArray agg_op, jbyteArray input_rows, jboolean isPartial) {

src/enclave/App/SGXEnclave.h

@@ -41,6 +41,10 @@ extern "C" {
   Java_edu_berkeley_cs_rise_opaque_execution_SGXEnclave_NonObliviousSortMergeJoin(
     JNIEnv *, jobject, jlong, jbyteArray, jbyteArray);
 
+  JNIEXPORT jbyteArray JNICALL
+  Java_edu_berkeley_cs_rise_opaque_execution_SGXEnclave_BroadcastNestedLoopJoin(
+    JNIEnv *, jobject, jlong, jbyteArray, jbyteArray, jbyteArray);
+
   JNIEXPORT jobject JNICALL
   Java_edu_berkeley_cs_rise_opaque_execution_SGXEnclave_NonObliviousAggregate(
     JNIEnv *, jobject, jlong, jbyteArray, jbyteArray, jboolean);

src/enclave/Enclave/BroadcastNestedLoopJoin.cpp

@@ -0,0 +1,54 @@
+#include "BroadcastNestedLoopJoin.h"
+
+#include "ExpressionEvaluation.h"
+#include "FlatbuffersReaders.h"
+#include "FlatbuffersWriters.h"
+#include "common.h"
+
+/** C++ implementation of a broadcast nested loop join.
+ * Assumes outer_rows is streamed and inner_rows is broadcast.
+ * DOES NOT rely on rows to be tagged primary or secondary, and that
+ * assumption will break the implementation.
+ */
+void broadcast_nested_loop_join(
+  uint8_t *join_expr, size_t join_expr_length,
+  uint8_t *outer_rows, size_t outer_rows_length,
+  uint8_t *inner_rows, size_t inner_rows_length,
+  uint8_t **output_rows, size_t *output_rows_length) {
+
+  FlatbuffersJoinExprEvaluator join_expr_eval(join_expr, join_expr_length);
+  const tuix::JoinType join_type = join_expr_eval.get_join_type();
+
+  RowReader outer_r(BufferRefView<tuix::EncryptedBlocks>(outer_rows, outer_rows_length));
+  RowWriter w;
+
+  while (outer_r.has_next()) {
+    const tuix::Row *outer = outer_r.next();
+    bool o_i_match = false;
+
+    RowReader inner_r(BufferRefView<tuix::EncryptedBlocks>(inner_rows, inner_rows_length));
+    const tuix::Row *inner;
+    while (inner_r.has_next()) {
+      inner = inner_r.next();
+      o_i_match |= join_expr_eval.eval_condition(outer, inner);
+    }
+
+    switch(join_type) {
+      case tuix::JoinType_LeftAnti:
+        if (!o_i_match) {
+          w.append(outer);
+        }
+        break;
+      case tuix::JoinType_LeftSemi:
+        if (o_i_match) {
+          w.append(outer);
+        }
+        break;
+      default:
+        throw std::runtime_error(
+          std::string("Join type not supported: ")
+          + std::string(to_string(join_type)));
+    }
+  }
+  w.output_buffer(output_rows, output_rows_length);
+}

src/enclave/Enclave/BroadcastNestedLoopJoin.h

@@ -0,0 +1,8 @@
+#include <cstddef>
+#include <cstdint>
+
+void broadcast_nested_loop_join(
+    uint8_t *join_expr, size_t join_expr_length,
+    uint8_t *outer_rows, size_t outer_rows_length,
+    uint8_t *inner_rows, size_t inner_rows_length,
+    uint8_t **output_rows, size_t *output_rows_length);

src/enclave/Enclave/CMakeLists.txt

@@ -10,7 +10,8 @@ set(SOURCES
   Flatbuffers.cpp
   FlatbuffersReaders.cpp
   FlatbuffersWriters.cpp
-  Join.cpp
+  NonObliviousSortMergeJoin.cpp
+  BroadcastNestedLoopJoin.cpp
   Limit.cpp
   Project.cpp
   Sort.cpp

src/enclave/Enclave/Enclave.cpp

@@ -6,7 +6,8 @@
 #include "Aggregate.h"
 #include "Crypto.h"
 #include "Filter.h"
-#include "Join.h"
+#include "NonObliviousSortMergeJoin.h"
+#include "BroadcastNestedLoopJoin.h"
 #include "Limit.h"
 #include "Project.h"
 #include "Sort.h"
@@ -161,6 +162,25 @@ void ecall_non_oblivious_sort_merge_join(uint8_t *join_expr, size_t join_expr_le
   }
 }
 
+void ecall_broadcast_nested_loop_join(uint8_t *join_expr, size_t join_expr_length,
+                                         uint8_t *outer_rows, size_t outer_rows_length,
+                                         uint8_t *inner_rows, size_t inner_rows_length,
+                                         uint8_t **output_rows, size_t *output_rows_length) {
+  // Guard against operating on arbitrary enclave memory
+  assert(oe_is_outside_enclave(outer_rows, outer_rows_length) == 1);
+  assert(oe_is_outside_enclave(inner_rows, inner_rows_length) == 1);
+  __builtin_ia32_lfence();
+
+  try {
+    broadcast_nested_loop_join(join_expr, join_expr_length,
+                                  outer_rows, outer_rows_length,
+                                  inner_rows, inner_rows_length,
+                                  output_rows, output_rows_length);
+  } catch (const std::runtime_error &e) {
+    ocall_throw(e.what());
+  }
+}
+
 void ecall_non_oblivious_aggregate(
   uint8_t *agg_op, size_t agg_op_length,
   uint8_t *input_rows, size_t input_rows_length,

src/enclave/Enclave/Enclave.edl

@@ -51,6 +51,12 @@ enclave {
       [user_check] uint8_t *input_rows, size_t input_rows_length,
       [out] uint8_t **output_rows, [out] size_t *output_rows_length);
 
+    public void ecall_broadcast_nested_loop_join(
+      [in, count=join_expr_length] uint8_t *join_expr, size_t join_expr_length,
+      [user_check] uint8_t *outer_rows, size_t outer_rows_length,
+      [user_check] uint8_t *inner_rows, size_t inner_rows_length,
+      [out] uint8_t **output_rows, [out] size_t *output_rows_length);
+
     public void ecall_non_oblivious_aggregate(
       [in, count=agg_op_length] uint8_t *agg_op, size_t agg_op_length,
       [user_check] uint8_t *input_rows, size_t input_rows_length,

src/enclave/Enclave/ExpressionEvaluation.h

@@ -1787,60 +1787,104 @@ class FlatbuffersJoinExprEvaluator {
     }
 
     const tuix::JoinExpr* join_expr = flatbuffers::GetRoot<tuix::JoinExpr>(buf);
-    join_type = join_expr->join_type();
 
-    if (join_expr->left_keys()->size() != join_expr->right_keys()->size()) {
-      throw std::runtime_error("Mismatched join key lengths");
-    }
-    for (auto key_it = join_expr->left_keys()->begin();
-         key_it != join_expr->left_keys()->end(); ++key_it) {
-      left_key_evaluators.emplace_back(
-        std::unique_ptr<FlatbuffersExpressionEvaluator>(
-          new FlatbuffersExpressionEvaluator(*key_it)));
+    join_type = join_expr->join_type();
+    if (join_expr->condition() != NULL) {
+      condition_eval = std::unique_ptr<FlatbuffersExpressionEvaluator>(
+          new FlatbuffersExpressionEvaluator(join_expr->condition()));
     }
-    for (auto key_it = join_expr->right_keys()->begin();
-         key_it != join_expr->right_keys()->end(); ++key_it) {
-      right_key_evaluators.emplace_back(
-        std::unique_ptr<FlatbuffersExpressionEvaluator>(
-          new FlatbuffersExpressionEvaluator(*key_it)));
+    is_equi_join = false;
+
+    if (join_expr->left_keys() != NULL && join_expr->right_keys() != NULL) {
+      is_equi_join = true;
+      if (join_expr->condition() != NULL) {
+        throw std::runtime_error("Equi join cannot have condition");
+      }
+      if (join_expr->left_keys()->size() != join_expr->right_keys()->size()) {
+        throw std::runtime_error("Mismatched join key lengths");
+      }
+      for (auto key_it = join_expr->left_keys()->begin();
+          key_it != join_expr->left_keys()->end(); ++key_it) {
+        left_key_evaluators.emplace_back(
+          std::unique_ptr<FlatbuffersExpressionEvaluator>(
+            new FlatbuffersExpressionEvaluator(*key_it)));
+      }
+      for (auto key_it = join_expr->right_keys()->begin();
+          key_it != join_expr->right_keys()->end(); ++key_it) {
+        right_key_evaluators.emplace_back(
+          std::unique_ptr<FlatbuffersExpressionEvaluator>(
+            new FlatbuffersExpressionEvaluator(*key_it)));
+      }
     }
   }
 
-  /**
-   * Return true if the given row is from the primary table, indicated by its first field, which
-   * must be an IntegerField.
+   /** Return true if the given row is from the primary table, indicated by its first field, which
+    * must be an IntegerField.
+    * Rows MUST have been tagged in Scala.
    */
   bool is_primary(const tuix::Row *row) {
     return static_cast<const tuix::IntegerField *>(
       row->field_values()->Get(0)->value())->value() == 0;
   }
 
-  /** Return true if the two rows are from the same join group. */
-  bool is_same_group(const tuix::Row *row1, const tuix::Row *row2) {
-    auto &row1_evaluators = is_primary(row1) ? left_key_evaluators : right_key_evaluators;
-    auto &row2_evaluators = is_primary(row2) ? left_key_evaluators : right_key_evaluators;
+  /** Returns the row evaluator corresponding to the primary row
+   * Rows MUST have been tagged in Scala.
+  */
+  const tuix::Row *get_primary_row(
+      const tuix::Row *row1, const tuix::Row *row2) {
+    return is_primary(row1) ? row1 : row2;
+  }
 
+  /** Return true if the two rows satisfy the join condition. */
+  bool eval_condition(const tuix::Row *row1, const tuix::Row *row2) {
     builder.Clear();
+    bool row1_equals_row2;
+
+    /** Check equality for equi joins. If it is a non-equi join, 
+     * the key evaluators will be empty, so the code never enters the for loop.
+    */
+    auto &row1_evaluators = is_primary(row1) ? left_key_evaluators : right_key_evaluators;
+    auto &row2_evaluators = is_primary(row2) ? left_key_evaluators : right_key_evaluators;
     for (uint32_t i = 0; i < row1_evaluators.size(); i++) {
       const tuix::Field *row1_eval_tmp = row1_evaluators[i]->eval(row1);
       auto row1_eval_offset = flatbuffers_copy(row1_eval_tmp, builder);
+      auto row1_field = flatbuffers::GetTemporaryPointer<tuix::Field>(builder, row1_eval_offset);
+
       const tuix::Field *row2_eval_tmp = row2_evaluators[i]->eval(row2);
       auto row2_eval_offset = flatbuffers_copy(row2_eval_tmp, builder);
+      auto row2_field = flatbuffers::GetTemporaryPointer<tuix::Field>(builder, row2_eval_offset);
 
-      bool row1_equals_row2 =
+      flatbuffers::Offset<tuix::Field> comparison = eval_binary_comparison<tuix::EqualTo, std::equal_to>(
+        builder,
+        row1_field,
+        row2_field);
+      row1_equals_row2 =
         static_cast<const tuix::BooleanField *>(
           flatbuffers::GetTemporaryPointer<tuix::Field>(
             builder,
-            eval_binary_comparison<tuix::EqualTo, std::equal_to>(
-              builder,
-              flatbuffers::GetTemporaryPointer<tuix::Field>(builder, row1_eval_offset),
-              flatbuffers::GetTemporaryPointer<tuix::Field>(builder, row2_eval_offset)))
-          ->value())->value();
+            comparison)->value())->value();
 
       if (!row1_equals_row2) {
         return false;
       }
     }
+
+    /* Check condition for non-equi joins */
+    if (!is_equi_join) {
+      std::vector<flatbuffers::Offset<tuix::Field>> concat_fields;
+      for (auto field : *row1->field_values()) {
+        concat_fields.push_back(flatbuffers_copy<tuix::Field>(field, builder));
+      }
+      for (auto field : *row2->field_values()) {
+        concat_fields.push_back(flatbuffers_copy<tuix::Field>(field, builder));
+      }
+      flatbuffers::Offset<tuix::Row> concat = tuix::CreateRowDirect(builder, &concat_fields);
+      const tuix::Row *concat_ptr = flatbuffers::GetTemporaryPointer<tuix::Row>(builder, concat);
+
+      const tuix::Field *condition_result = condition_eval->eval(concat_ptr);
+
+      return static_cast<const tuix::BooleanField *>(condition_result->value())->value();
+    }
     return true;
   }
 
@@ -1853,6 +1897,8 @@ class FlatbuffersJoinExprEvaluator {
   tuix::JoinType join_type;
   std::vector<std::unique_ptr<FlatbuffersExpressionEvaluator>> left_key_evaluators;
   std::vector<std::unique_ptr<FlatbuffersExpressionEvaluator>> right_key_evaluators;
+  bool is_equi_join;
+  std::unique_ptr<FlatbuffersExpressionEvaluator> condition_eval;
 };
 
 class AggregateExpressionEvaluator {

src/enclave/Enclave/Join.cpp → src/enclave/Enclave/NonObliviousSortMergeJoin.cpp

@@ -1,10 +1,13 @@
-#include "Join.h"
+#include "NonObliviousSortMergeJoin.h"
 
 #include "ExpressionEvaluation.h"
 #include "FlatbuffersReaders.h"
 #include "FlatbuffersWriters.h"
 #include "common.h"
 
+/** C++ implementation of a non-oblivious sort merge join.
+ * Rows MUST be tagged primary or secondary for this to work.
+ */
 void non_oblivious_sort_merge_join(
   uint8_t *join_expr, size_t join_expr_length,
   uint8_t *input_rows, size_t input_rows_length,
@@ -25,7 +28,7 @@ void non_oblivious_sort_merge_join(
 
     if (join_expr_eval.is_primary(current)) {
       if (last_primary_of_group.get()
-          && join_expr_eval.is_same_group(last_primary_of_group.get(), current)) {
+          && join_expr_eval.eval_condition(last_primary_of_group.get(), current)) {
         // Add this primary row to the current group
         primary_group.append(current);
         last_primary_of_group.set(current);
@@ -50,13 +53,13 @@ void non_oblivious_sort_merge_join(
     } else {
       // Output the joined rows resulting from this foreign row
       if (last_primary_of_group.get()
-          && join_expr_eval.is_same_group(last_primary_of_group.get(), current)) {
+          && join_expr_eval.eval_condition(last_primary_of_group.get(), current)) {
         auto primary_group_buffer = primary_group.output_buffer();
         RowReader primary_group_reader(primary_group_buffer.view());
         while (primary_group_reader.has_next()) {
           const tuix::Row *primary = primary_group_reader.next();
 
-          if (!join_expr_eval.is_same_group(primary, current)) {
+          if (!join_expr_eval.eval_condition(primary, current)) {
             throw std::runtime_error(
               std::string("Invariant violation: rows of primary_group "
                           "are not of the same group: ")

src/enclave/Enclave/Join.h → src/enclave/Enclave/NonObliviousSortMergeJoin.h

@@ -1,12 +1,7 @@
 #include <cstddef>
 #include <cstdint>
 
-#ifndef JOIN_H
-#define JOIN_H
-
 void non_oblivious_sort_merge_join(
     uint8_t *join_expr, size_t join_expr_length,
     uint8_t *input_rows, size_t input_rows_length,
     uint8_t **output_rows, size_t *output_rows_length);
-
-#endif

src/flatbuffers/operators.fbs

@@ -54,10 +54,11 @@ enum JoinType : ubyte {
 }
 table JoinExpr {
     join_type:JoinType;
-    // Currently only cross joins and equijoins are supported, so we store
-    // parallel arrays of key expressions and the join outputs pairs of rows
-    // where each expression from the left is equal to the matching expression
-    // from the right.
+    // In the case of equi joins, we store parallel arrays of key expressions and have the join output
+    // pairs of rows  where each expression from the left is equal to the matching expression from the right.
     left_keys:[Expr];
     right_keys:[Expr];
+    // In the case of non-equi joins, we pass in a condition as an expression and evaluate that on each pair of rows.
+    // TODO: have equi joins use this condition rather than an additional filter operation.
+    condition:Expr;
 }