// For this version, the work flow is that we first lookup the left table, and
// use the result to lookup right table. If left table is done that means right
// table is also done. So we only keep the left_child_done_ as the sign.
bool NestedLoopJoinExecutor::DExecute() {
LOG_TRACE("********** Nested Loop %s Join executor :: 2 children ",
GetJoinTypeString());
// Grab info from plan node and check it
const planner::NestedLoopJoinPlan &node =
GetPlanNode<planner::NestedLoopJoinPlan>();
// Pick out the left and right columns
const std::vector<oid_t> &join_column_ids_left = node.GetJoinColumnsLeft();
const std::vector<oid_t> &join_column_ids_right = node.GetJoinColumnsRight();
// We should first deal with the current result. Otherwise we will cache a lot
// data which is not good to utilize memory. After that we call child execute.
// Since is the high level idea, each time we get tile from left, we should
// finish this tile, and then call child[0] execute for next tile.
for (;;) {
//===------------------------------------------------------------------===//
// Pick left and right tiles
//===------------------------------------------------------------------===//
// If we have already retrieved all left child's results in buffer
if (left_child_done_ == true) {
LOG_TRACE("Left is done which means all join comparison completes");
return false;
}
// If left tile result is not done, continue the left tuples
if (!left_tile_done_) {
// Tuple result
ContainerTuple<executor::LogicalTile> left_tuple(left_tile_.get(),
left_tile_row_itr_);
// Grab the values
if (!join_column_ids_left.empty() && !join_column_ids_right.empty()) {
std::vector<type::Value> join_values;
for (auto column_id : join_column_ids_left) {
type::Value predicate_value = left_tuple.GetValue(column_id);
join_values.push_back(predicate_value);
}
// Pass the columns and values to right executor
LOG_TRACE("Update the new value for index predicate");
children_[1]->UpdatePredicate(join_column_ids_right, join_values);
}
// Execute the right child to get the right tile
if (children_[1]->Execute() == true) {
LOG_TRACE("Advance the Right child.");
std::unique_ptr<LogicalTile> right_tile(children_[1]->GetOutput());
PL_ASSERT(right_tile != nullptr);
// Construct output result
auto output_tile =
BuildOutputLogicalTile(left_tile_.get(), right_tile.get());
// Build position list
LogicalTile::PositionListsBuilder pos_lists_builder(left_tile_.get(),
right_tile.get());
// Go over every pair of tuples in left and right logical tiles
for (auto right_tile_row_itr : *right_tile) {
// Insert a tuple into the output logical tile
// First, copy the elements in left logical tile's tuple
LOG_TRACE("Insert a tuple into the output logical tile");
ContainerTuple<executor::LogicalTile> right_tuple(right_tile.get(),
right_tile_row_itr);
if (predicate_ != nullptr) {
auto eval = predicate_->Evaluate(&left_tuple, &right_tuple,
executor_context_);
// Join predicate is false. Skip pair and continue.
if (eval.IsFalse()) {
LOG_TRACE("Not math join predicate");
continue;
}
LOG_TRACE("Find a tuple with join predicate");
}
pos_lists_builder.AddRow(left_tile_row_itr_, right_tile_row_itr);
} // Outer loop of NLJ
// Now current left tile is done
LOG_TRACE("pos_lists_builder's size : %ld", pos_lists_builder.Size());
if (pos_lists_builder.Size() > 0) {
LOG_TRACE("Set output result");
output_tile->SetPositionListsAndVisibility(
pos_lists_builder.Release());
SetOutput(output_tile.release());
LOG_TRACE("result is : %s", GetOutputInfo()->GetInfo().c_str());
return true;
}
continue;
}
// Right table is finished for the current left tuple. move to the next
else {
if (!left_child_done_) {
LOG_TRACE("right child is done, but left is not, so reset right");
children_[1]->ResetState();
// When all right table is done, examine whether left tile is done
// If left tile is done, next loop will directly execute child[0]
if (left_tile_row_itr_ == left_tile_->GetTupleCount() - 1) {
LOG_TRACE("left tile is done");
// Set up flag and go the execute child 0 to get the next tile
left_tile_done_ = true;
} else {
// Move the row to the next one in left tile
LOG_TRACE("Advance left row");
left_tile_row_itr_++;
// Continue the new left row
continue;
}
} else {
LOG_TRACE("Both left and right child are done");
right_child_done_ = true;
return false;
}
}
} // End handle left tile
// Otherwise, we must attempt to execute the left child to get a new left
// tile
// Left child is finished, no more tiles
if (children_[0]->Execute() == false) {
LOG_TRACE("Left child is exhausted.");
return false;
}
// Cache the new tile
else {
// Get the left child's result
LOG_TRACE("Retrieve a new tile from left child");
left_tile_.reset(children_[0]->GetOutput());
// Set the flag with init status
left_tile_done_ = false;
left_tile_row_itr_ = 0;
}
LOG_TRACE("Get a new left tile. Continue the loop.");
} // end the very beginning for loop
}
/**
* @brief Creates logical tiles from the two input logical tiles after applying
* join predicate.
* @return true on success, false otherwise.
*
* ExecutorContext is set when executing IN+NestLoop. For example:
* select * from Foo1 where age IN (select id from Foo2 where name='mike');
* Here:
* "select id from Foo2 where name='mike'" is transformed as left child.
* "select * from Foo1 where age " is the right child.
* "IN" is transformed as a execute context, in NestLoop
* We put the results of left child in executor_context using NestLoop, and the
* right child can execute using this context. Otherwise, the right child can't
* execute. And there is no predicate_ for IN+NestLoop
*
* For now, we only set this context for IN operator. Normally, the right child
* has a complete query that can execute without the context, and we use predicate_
* to join the left and right result.
*
*/
bool NestedLoopJoinExecutor::DExecute() {
LOG_INFO("********** Nested Loop %s Join executor :: 2 children ",
GetJoinTypeString());
// Loop until we have non-empty result tile or exit
for (;;) {
// Build outer join output when done
if (left_child_done_ && right_child_done_) {
return BuildOuterJoinOutput();
}
//===------------------------------------------------------------------===//
// Pick left and right tiles
//===------------------------------------------------------------------===//
LogicalTile *left_tile = nullptr;
LogicalTile *right_tile = nullptr;
bool advance_right_child = false;
// If we have already retrieved all left child's results in buffer
if (left_child_done_ == true) {
LOG_TRACE("Advance the left buffer iterator.");
assert(!right_result_tiles_.empty());
left_result_itr_++;
if (left_result_itr_ >= left_result_tiles_.size()) {
advance_right_child = true;
left_result_itr_ = 0;
}
}
// Otherwise, we must attempt to execute the left child
else {
// Left child is finished, no more tiles
if (children_[0]->Execute() == false) {
LOG_TRACE("Left child is exhausted.");
left_child_done_ = true;
left_result_itr_ = 0;
advance_right_child = true;
}
// Buffer the left child's result
else {
LOG_TRACE("Retrieve a new tile from left child");
BufferLeftTile(children_[0]->GetOutput());
left_result_itr_ = left_result_tiles_.size() - 1;
}
}
if (advance_right_child == true || right_result_tiles_.empty()) {
// return if right tile is empty
if (right_child_done_ && right_result_tiles_.empty()) {
return BuildOuterJoinOutput();
}
assert(left_result_itr_ == 0);
// Right child is finished, no more tiles
if (children_[1]->Execute() == false) {
LOG_TRACE("Right child is exhausted. Returning false.");
// Right child exhausted.
// Release cur Right tile. Clear right child's result buffer and return.
right_child_done_ = true;
return BuildOuterJoinOutput();
}
// Buffer the Right child's result
else {
LOG_TRACE("Advance the Right child.");
BufferRightTile(children_[1]->GetOutput());
// return if left tile is empty
if (left_child_done_ && left_result_tiles_.empty()) {
return BuildOuterJoinOutput();
}
}
}
right_tile = right_result_tiles_.back().get();
left_tile = left_result_tiles_[left_result_itr_].get();
//===------------------------------------------------------------------===//
// Build Join Tile
//===------------------------------------------------------------------===//
// Build output logical tile
auto output_tile = BuildOutputLogicalTile(left_tile, right_tile);
// Build position lists
LogicalTile::PositionListsBuilder pos_lists_builder(left_tile, right_tile);
// Go over every pair of tuples in left and right logical tiles
for (auto right_tile_row_itr : *right_tile) {
bool has_left_match = false;
for (auto left_tile_row_itr : *left_tile) {
// Join predicate exists
if (predicate_ != nullptr) {
expression::ContainerTuple<executor::LogicalTile> left_tuple(
left_tile, left_tile_row_itr);
expression::ContainerTuple<executor::LogicalTile> right_tuple(
right_tile, right_tile_row_itr);
// Join predicate is false. Skip pair and continue.
if (predicate_->Evaluate(&left_tuple, &right_tuple, executor_context_)
.IsFalse()) {
continue;
}
}
RecordMatchedLeftRow(left_result_itr_, left_tile_row_itr);
// For Left and Full Outer Join
has_left_match = true;
// Insert a tuple into the output logical tile
// First, copy the elements in left logical tile's tuple
pos_lists_builder.AddRow(left_tile_row_itr, right_tile_row_itr);
} // Inner loop of NLJ
// For Right and Full Outer Join
if (has_left_match) {
RecordMatchedRightRow(right_result_tiles_.size() - 1,
right_tile_row_itr);
}
} // Outer loop of NLJ
// Check if we have any join tuples.
if (pos_lists_builder.Size() > 0) {
output_tile->SetPositionListsAndVisibility(pos_lists_builder.Release());
SetOutput(output_tile.release());
return true;
}
LOG_TRACE("This pair produces empty join result. Continue the loop.");
} // end the very beginning for loop
}
/**
* @brief Creates logical tiles from the two input logical tiles after applying
* join predicate.
* @return true on success, false otherwise.
*/
bool MergeJoinExecutor::DExecute() {
LOG_INFO(
"********** Merge Join executor :: 2 children "
"left:: start: %lu, end: %lu, done: %d "
"right:: start: %lu, end: %lu, done: %d",
left_start_row, left_end_row, left_child_done_, right_start_row,
right_end_row, right_child_done_);
// Build outer join output when done
if (right_child_done_ && left_child_done_) {
return BuildOuterJoinOutput();
}
//===--------------------------------------------------------------------===//
// Pick right and left tiles
//===--------------------------------------------------------------------===//
// Try to get next tile from RIGHT child
if (((right_child_done_ == false) && (right_start_row == right_end_row)) ||
(left_child_done_ == true)) {
if (children_[1]->Execute() == false) {
LOG_TRACE("Did not get right tile ");
right_child_done_ = true;
// Try again
return DExecute();
}
LOG_TRACE("Got right tile ");
auto right_tile = children_[1]->GetOutput();
BufferRightTile(right_tile);
right_start_row = 0;
right_end_row = Advance(right_tile, right_start_row, false);
LOG_TRACE("size of right tiles: %lu", right_result_tiles_.size());
}
// Try to get next tile from LEFT child
if (((left_child_done_ == false) && (left_start_row == left_end_row)) ||
(right_child_done_ == true)) {
if (children_[0]->Execute() == false) {
LOG_TRACE("Did not get left tile ");
left_child_done_ = true;
// Try again
return DExecute();
}
LOG_TRACE("Got left tile ");
auto left_tile = children_[0]->GetOutput();
BufferLeftTile(left_tile);
left_start_row = 0;
left_end_row = Advance(left_tile, left_start_row, true);
LOG_TRACE("size of left tiles: %lu", left_result_tiles_.size());
}
// Check if we have logical tiles to process
if(left_result_tiles_.empty() || right_result_tiles_.empty()) {
return false;
}
LogicalTile *left_tile = left_result_tiles_.back().get();
LogicalTile *right_tile = right_result_tiles_.back().get();
//===--------------------------------------------------------------------===//
// Build Join Tile
//===--------------------------------------------------------------------===//
// Build output logical tile
auto output_tile = BuildOutputLogicalTile(left_tile, right_tile);
// Build position lists
LogicalTile::PositionListsBuilder pos_lists_builder(left_tile, right_tile);
while ((left_end_row > left_start_row) && (right_end_row > right_start_row)) {
expression::ContainerTuple<executor::LogicalTile> left_tuple(
left_tile, left_start_row);
expression::ContainerTuple<executor::LogicalTile> right_tuple(
right_tile, right_start_row);
bool not_matching_tuple_pair = false;
// Evaluate and compare the join clauses
for (auto &clause : *join_clauses_) {
auto left_value =
clause.left_->Evaluate(&left_tuple, &right_tuple, nullptr);
auto right_value =
clause.right_->Evaluate(&left_tuple, &right_tuple, nullptr);
// Compare the values
int comparison = left_value.Compare(right_value);
// Left key < Right key, advance left
if (comparison < 0) {
LOG_TRACE("left < right, advance left ");
left_start_row = left_end_row;
left_end_row = Advance(left_tile, left_start_row, true);
not_matching_tuple_pair = true;
break;
}
// Left key > Right key, advance right
else if (comparison > 0) {
LOG_TRACE("left > right, advance right ");
right_start_row = right_end_row;
right_end_row = Advance(right_tile, right_start_row, false);
not_matching_tuple_pair = true;
break;
}
// Left key == Right key, go and check next join clause
}
// Atleast one of the join clauses don't match
// One of the tile has been advanced
if (not_matching_tuple_pair) {
continue;
}
// Join clauses matched, try to match predicate
LOG_TRACE("one pair of tuples matches join clause ");
// Join predicate exists
if (predicate_ != nullptr) {
if (predicate_->Evaluate(&left_tuple, &right_tuple, executor_context_)
.IsFalse()) {
// Join predicate is false. Advance both.
left_start_row = left_end_row;
left_end_row = Advance(left_tile, left_start_row, true);
right_start_row = right_end_row;
right_end_row = Advance(right_tile, right_start_row, false);
}
}
// Sub tile matched, do a Cartesian product
// Go over every pair of tuples in left and right logical tiles
for (size_t left_tile_row_itr = left_start_row;
left_tile_row_itr < left_end_row; left_tile_row_itr++) {
for (size_t right_tile_row_itr = right_start_row;
right_tile_row_itr < right_end_row; right_tile_row_itr++) {
// Insert a tuple into the output logical tile
pos_lists_builder.AddRow(left_tile_row_itr, right_tile_row_itr);
RecordMatchedLeftRow(left_result_tiles_.size() - 1, left_tile_row_itr);
RecordMatchedRightRow(right_result_tiles_.size() - 1,
right_tile_row_itr);
}
}
// Then, advance both
left_start_row = left_end_row;
left_end_row = Advance(left_tile, left_start_row, true);
right_start_row = right_end_row;
right_end_row = Advance(right_tile, right_start_row, false);
}
// Check if we have any join tuples.
if (pos_lists_builder.Size() > 0) {
output_tile->SetPositionListsAndVisibility(pos_lists_builder.Release());
SetOutput(output_tile.release());
return true;
}
// Try again
else {
// If we are out of any more pairs of child tiles to examine,
// then we will return false earlier in this function
// So, no need to return false here
DExecute();
}
return true;
}
