be/src/exec/select-node.cc

// Licensed to the Apache Software Foundation (ASF) under one
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// regarding copyright ownership.  The ASF licenses this file
// to you under the Apache License, Version 2.0 (the
// "License"); you may not use this file except in compliance
// with the License.  You may obtain a copy of the License at
//
//   http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing,
// software distributed under the License is distributed on an
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// specific language governing permissions and limitations
// under the License.

#include "exec/select-node.h"
#include "exprs/expr.h"
#include "runtime/row-batch.h"
#include "runtime/runtime-state.h"
#include "runtime/raw-value.h"
#include "util/runtime-profile-counters.h"
#include "gen-cpp/PlanNodes_types.h"

#include "common/names.h"

namespace impala {

SelectNode::SelectNode(
    ObjectPool* pool, const TPlanNode& tnode, const DescriptorTbl& descs)
    : ExecNode(pool, tnode, descs),
      child_row_batch_(NULL),
      child_row_idx_(0),
      child_eos_(false) {
}

Status SelectNode::Prepare(RuntimeState* state) {
  SCOPED_TIMER(runtime_profile_->total_time_counter());
  RETURN_IF_ERROR(ExecNode::Prepare(state));
  return Status::OK();
}

Status SelectNode::Open(RuntimeState* state) {
  SCOPED_TIMER(runtime_profile_->total_time_counter());
  RETURN_IF_ERROR(ExecNode::Open(state));
  RETURN_IF_ERROR(child(0)->Open(state));
  child_row_batch_.reset(
      new RowBatch(child(0)->row_desc(), state->batch_size(), mem_tracker()));
  return Status::OK();
}

Status SelectNode::GetNext(RuntimeState* state, RowBatch* row_batch, bool* eos) {
  SCOPED_TIMER(runtime_profile_->total_time_counter());
  RETURN_IF_ERROR(ExecDebugAction(TExecNodePhase::GETNEXT, state));

  if (ReachedLimit() || (child_row_idx_ == child_row_batch_->num_rows() && child_eos_)) {
    // we're already done or we exhausted the last child batch and there won't be any
    // new ones
    *eos = true;
    child_row_batch_->TransferResourceOwnership(row_batch);
    return Status::OK();
  }
  *eos = false;

  // start (or continue) consuming row batches from child
  while (true) {
    RETURN_IF_CANCELLED(state);
    RETURN_IF_ERROR(QueryMaintenance(state));
    if (child_row_idx_ == child_row_batch_->num_rows()) {
      child_row_idx_ = 0;
      // fetch next batch
      child_row_batch_->TransferResourceOwnership(row_batch);
      child_row_batch_->Reset();
      if (row_batch->AtCapacity()) return Status::OK();
      RETURN_IF_ERROR(child(0)->GetNext(state, child_row_batch_.get(), &child_eos_));
    }

    if (CopyRows(row_batch)) {
      *eos = ReachedLimit()
          || (child_row_idx_ == child_row_batch_->num_rows() && child_eos_);
      if (*eos) child_row_batch_->TransferResourceOwnership(row_batch);
      return Status::OK();
    }
    if (child_eos_) {
      // finished w/ last child row batch, and child eos is true
      child_row_batch_->TransferResourceOwnership(row_batch);
      *eos = true;
      return Status::OK();
    }
  }
  return Status::OK();
}

bool SelectNode::CopyRows(RowBatch* output_batch) {
  ExprContext** conjunct_ctxs = &conjunct_ctxs_[0];
  int num_conjunct_ctxs = conjunct_ctxs_.size();

  while (child_row_idx_ < child_row_batch_->num_rows()) {
    // Add a new row to output_batch
    int dst_row_idx = output_batch->AddRow();
    TupleRow* dst_row = output_batch->GetRow(dst_row_idx);
    TupleRow* src_row = child_row_batch_->GetRow(child_row_idx_);
    // Make sure to increment row idx before returning.
    ++child_row_idx_;

    if (EvalConjuncts(conjunct_ctxs, num_conjunct_ctxs, src_row)) {
      output_batch->CopyRow(src_row, dst_row);
      output_batch->CommitLastRow();
      ++num_rows_returned_;
      COUNTER_SET(rows_returned_counter_, num_rows_returned_);
      if (ReachedLimit() || output_batch->AtCapacity()) return true;
    }
  }
  return output_batch->AtCapacity();
}

Status SelectNode::Reset(RuntimeState* state) {
  child_row_batch_->Reset();
  child_row_idx_ = 0;
  child_eos_ = false;
  return ExecNode::Reset(state);
}

void SelectNode::Close(RuntimeState* state) {
  if (is_closed()) return;
  child_row_batch_.reset();
  ExecNode::Close(state);
}

}