121 lines
4.3 KiB
C++
121 lines
4.3 KiB
C++
// Licensed to the Apache Software Foundation (ASF) under one
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// or more contributor license agreements. See the NOTICE file
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// distributed with this work for additional information
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// regarding copyright ownership. The ASF licenses this file
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// to you under the Apache License, Version 2.0 (the
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// "License"); you may not use this file except in compliance
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// with the License. You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing,
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// software distributed under the License is distributed on an
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// "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
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// KIND, either express or implied. See the License for the
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// specific language governing permissions and limitations
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// under the License.
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#ifndef DORIS_BE_SRC_QUERY_EXEC_TOPN_NODE_H
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#define DORIS_BE_SRC_QUERY_EXEC_TOPN_NODE_H
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#include <boost/scoped_ptr.hpp>
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#include <queue>
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#include "exec/exec_node.h"
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#include "runtime/descriptors.h"
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#include "util/tuple_row_compare.h"
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namespace doris {
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class MemPool;
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class RuntimeState;
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class Tuple;
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// Node for in-memory TopN (ORDER BY ... LIMIT)
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// This handles the case where the result fits in memory. This node will do a deep
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// copy of the tuples that are necessary for the output.
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// This is implemented by storing rows in a priority queue.
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class TopNNode : public ExecNode {
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public:
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TopNNode(ObjectPool* pool, const TPlanNode& tnode, const DescriptorTbl& descs);
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virtual ~TopNNode();
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virtual Status init(const TPlanNode& tnode, RuntimeState* state = nullptr);
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virtual Status prepare(RuntimeState* state);
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virtual Status open(RuntimeState* state);
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virtual Status get_next(RuntimeState* state, RowBatch* row_batch, bool* eos);
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virtual Status close(RuntimeState* state);
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virtual void push_down_predicate(
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RuntimeState *state, std::list<ExprContext*> *expr_ctxs);
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protected:
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virtual void debug_string(int indentation_level, std::stringstream* out) const;
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private:
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friend class TupleLessThan;
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// Inserts a tuple row into the priority queue if it's in the TopN. Creates a deep
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// copy of tuple_row, which it stores in _tuple_pool.
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void insert_tuple_row(TupleRow* tuple_row);
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// Flatten and reverse the priority queue.
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void prepare_for_output();
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// number rows to skipped
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int64_t _offset;
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// _sort_exec_exprs contains the ordering expressions used for tuple comparison and
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// the materialization exprs for the output tuple.
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SortExecExprs _sort_exec_exprs;
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std::vector<bool> _is_asc_order;
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std::vector<bool> _nulls_first;
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// Cached descriptor for the materialized tuple. Assigned in Prepare().
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TupleDescriptor* _materialized_tuple_desc;
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// Comparator for _priority_queue.
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boost::scoped_ptr<TupleRowComparator> _tuple_row_less_than;
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// After computing the TopN in the priority_queue, pop them and put them in this vector
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std::vector<Tuple*> _sorted_top_n;
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// Tuple allocated once from _tuple_pool and reused in InsertTupleRow to
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// materialize input tuples if necessary. After materialization, _tmp_tuple may be
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// copied into the tuple pool and inserted into the priority queue.
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Tuple* _tmp_tuple;
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// Stores everything referenced in _priority_queue
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boost::scoped_ptr<MemPool> _tuple_pool;
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// Iterator over elements in _sorted_top_n.
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std::vector<Tuple*>::iterator _get_next_iter;
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// std::vector<TupleRow*>::iterator _get_next_iter;
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// True if the _limit comes from DEFAULT_ORDER_BY_LIMIT and the query option
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// ABORT_ON_DEFAULT_LIMIT_EXCEEDED is set.
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bool _abort_on_default_limit_exceeded;
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/////////////////////////////////////////
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// BEGIN: Members that must be Reset()
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// Number of rows skipped. Used for adhering to _offset.
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int64_t _num_rows_skipped;
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// The priority queue will never have more elements in it than the LIMIT. The stl
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// priority queue doesn't support a max size, so to get that functionality, the order
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// of the queue is the opposite of what the ORDER BY clause specifies, such that the top
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// of the queue is the last sorted element.
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boost::scoped_ptr<
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std::priority_queue<
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Tuple*, std::vector<Tuple*>, TupleRowComparator>> _priority_queue;
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// END: Members that must be Reset()
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/////////////////////////////////////////
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};
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};
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#endif
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