3894de49d2
This PR optimize topn query like `SELECT * FROM tableX ORDER BY columnA ASC/DESC LIMIT N`. TopN is is compose of SortNode and ScanNode, when user table is wide like 100+ columns the order by clause is just a few columns.But ScanNode need to scan all data from storage engine even if the limit is very small.This may lead to lots of read amplification.So In this PR I devide TopN query into two phase: 1. The first phase we just need to read `columnA`'s data from storage engine along with an extra RowId column called `__DORIS_ROWID_COL__`.The other columns are pruned from ScanNode. 2. The second phase I put it in the ExchangeNode beacuase it's the central node for topn nodes in the cluster.The ExchangeNode will spawn a RPC to other nodes using the RowIds(sorted and limited from SortNode) read from the first phase and read row by row from storage engine. After the second phase read, Block will contain all the data needed for the query
81 lines
2.8 KiB
C++
81 lines
2.8 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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#include "vec/exprs/vslot_ref.h"
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#include <fmt/format.h>
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#include "runtime/descriptors.h"
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namespace doris::vectorized {
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VSlotRef::VSlotRef(const doris::TExprNode& node)
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: VExpr(node), _slot_id(node.slot_ref.slot_id), _column_id(-1), _column_name(nullptr) {
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if (node.__isset.is_nullable) {
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_is_nullable = node.is_nullable;
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} else {
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_is_nullable = true;
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}
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}
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VSlotRef::VSlotRef(const SlotDescriptor* desc)
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: VExpr(desc->type(), true, desc->is_nullable()),
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_slot_id(desc->id()),
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_column_id(-1),
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_is_nullable(desc->is_nullable()),
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_column_name(nullptr) {}
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Status VSlotRef::prepare(doris::RuntimeState* state, const doris::RowDescriptor& desc,
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VExprContext* context) {
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RETURN_IF_ERROR_OR_PREPARED(VExpr::prepare(state, desc, context));
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DCHECK_EQ(_children.size(), 0);
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if (_slot_id == -1) {
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return Status::OK();
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}
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const SlotDescriptor* slot_desc = state->desc_tbl().get_slot_descriptor(_slot_id);
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if (slot_desc == nullptr) {
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return Status::InternalError("couldn't resolve slot descriptor {}", _slot_id);
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}
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_column_name = &slot_desc->col_name();
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if (!slot_desc->need_materialize()) {
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// slot should be ignored manually
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_column_id = -1;
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return Status::OK();
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}
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_column_id = desc.get_column_id(_slot_id);
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if (_column_id < 0) {
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LOG(INFO) << "VSlotRef - invalid slot id: " << _slot_id << " desc:" << desc.debug_string();
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return Status::InternalError("VSlotRef - invalid slot id {}", _slot_id);
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}
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return Status::OK();
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}
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Status VSlotRef::execute(VExprContext* context, Block* block, int* result_column_id) {
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*result_column_id = _column_id;
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return Status::OK();
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}
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const std::string& VSlotRef::expr_name() const {
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return *_column_name;
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}
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std::string VSlotRef::debug_string() const {
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std::stringstream out;
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out << "SlotRef(slot_id=" << _slot_id << VExpr::debug_string() << ")";
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return out.str();
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}
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} // namespace doris::vectorized
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