ClickHouse/dbms/src/Interpreters/InterpreterSelectWithUnionQuery.cpp

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#include <Interpreters/InterpreterSelectWithUnionQuery.h>
#include <Interpreters/InterpreterSelectQuery.h>
#include <Parsers/ASTSelectWithUnionQuery.h>
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#include <Parsers/ASTSelectQuery.h>
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#include <DataStreams/UnionBlockInputStream.h>
#include <DataStreams/NullBlockInputStream.h>
#include <DataStreams/ConcatBlockInputStream.h>
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#include <DataStreams/ConvertingBlockInputStream.h>
#include <DataTypes/getLeastSupertype.h>
#include <Columns/ColumnConst.h>
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#include <Common/typeid_cast.h>
#include <Parsers/queryToString.h>
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namespace DB
{
namespace ErrorCodes
{
extern const int LOGICAL_ERROR;
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extern const int UNION_ALL_RESULT_STRUCTURES_MISMATCH;
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}
InterpreterSelectWithUnionQuery::InterpreterSelectWithUnionQuery(
const ASTPtr & query_ptr_,
const Context & context_,
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const Names & required_result_column_names,
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QueryProcessingStage::Enum to_stage_,
size_t subquery_depth_,
bool only_analyze)
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: query_ptr(query_ptr_),
context(context_),
to_stage(to_stage_),
subquery_depth(subquery_depth_)
{
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const ASTSelectWithUnionQuery & ast = typeid_cast<const ASTSelectWithUnionQuery &>(*query_ptr);
size_t num_selects = ast.list_of_selects->children.size();
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if (!num_selects)
throw Exception("Logical error: no children in ASTSelectWithUnionQuery", ErrorCodes::LOGICAL_ERROR);
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/// Initialize interpreters for each SELECT query.
/// Note that we pass 'required_result_column_names' to first SELECT.
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/// And for the rest, we pass names at the corresponding positions of 'required_result_column_names' in the result of first SELECT,
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/// because names could be different.
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nested_interpreters.reserve(num_selects);
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std::vector<Names> required_result_column_names_for_other_selects(num_selects);
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if (!required_result_column_names.empty() && num_selects > 1)
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{
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/// Result header if there are no filtering by 'required_result_column_names'.
/// We use it to determine positions of 'required_result_column_names' in SELECT clause.
Block full_result_header = InterpreterSelectQuery(
ast.list_of_selects->children.at(0), context, Names(), to_stage, subquery_depth, true).getSampleBlock();
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std::vector<size_t> positions_of_required_result_columns(required_result_column_names.size());
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for (size_t required_result_num = 0, size = required_result_column_names.size(); required_result_num < size; ++required_result_num)
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positions_of_required_result_columns[required_result_num] = full_result_header.getPositionByName(required_result_column_names[required_result_num]);
for (size_t query_num = 1; query_num < num_selects; ++query_num)
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{
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Block full_result_header_for_current_select = InterpreterSelectQuery(
ast.list_of_selects->children.at(query_num), context, Names(), to_stage, subquery_depth, true).getSampleBlock();
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if (full_result_header_for_current_select.columns() != full_result_header.columns())
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throw Exception("Different number of columns in UNION ALL elements:\n"
+ full_result_header.dumpNames()
+ "\nand\n"
+ full_result_header_for_current_select.dumpNames() + "\n",
ErrorCodes::UNION_ALL_RESULT_STRUCTURES_MISMATCH);
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required_result_column_names_for_other_selects[query_num].reserve(required_result_column_names.size());
for (const auto & pos : positions_of_required_result_columns)
required_result_column_names_for_other_selects[query_num].push_back(full_result_header_for_current_select.getByPosition(pos).name);
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}
}
for (size_t query_num = 0; query_num < num_selects; ++query_num)
{
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const Names & current_required_result_column_names = query_num == 0
? required_result_column_names
: required_result_column_names_for_other_selects[query_num];
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nested_interpreters.emplace_back(std::make_unique<InterpreterSelectQuery>(
ast.list_of_selects->children.at(query_num), context, current_required_result_column_names, to_stage, subquery_depth, only_analyze));
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}
/// Determine structure of the result.
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if (num_selects == 1)
{
result_header = nested_interpreters.front()->getSampleBlock();
}
else
{
Blocks headers(num_selects);
for (size_t query_num = 0; query_num < num_selects; ++query_num)
headers[query_num] = nested_interpreters[query_num]->getSampleBlock();
result_header = headers.front();
size_t num_columns = result_header.columns();
for (size_t query_num = 1; query_num < num_selects; ++query_num)
if (headers[query_num].columns() != num_columns)
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throw Exception("Different number of columns in UNION ALL elements:\n"
+ result_header.dumpNames()
+ "\nand\n"
+ headers[query_num].dumpNames() + "\n",
ErrorCodes::UNION_ALL_RESULT_STRUCTURES_MISMATCH);
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for (size_t column_num = 0; column_num < num_columns; ++column_num)
{
ColumnWithTypeAndName & result_elem = result_header.getByPosition(column_num);
/// Determine common type.
DataTypes types(num_selects);
for (size_t query_num = 0; query_num < num_selects; ++query_num)
types[query_num] = headers[query_num].getByPosition(column_num).type;
result_elem.type = getLeastSupertype(types);
/// If there are different constness or different values of constants, the result must be non-constant.
if (result_elem.column->isColumnConst())
{
bool need_materialize = false;
for (size_t query_num = 1; query_num < num_selects; ++query_num)
{
const ColumnWithTypeAndName & source_elem = headers[query_num].getByPosition(column_num);
if (!source_elem.column->isColumnConst()
|| (static_cast<const ColumnConst &>(*result_elem.column).getField()
!= static_cast<const ColumnConst &>(*source_elem.column).getField()))
{
need_materialize = true;
break;
}
}
if (need_materialize)
result_elem.column = result_elem.type->createColumn();
}
/// BTW, result column names are from first SELECT.
}
}
}
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InterpreterSelectWithUnionQuery::~InterpreterSelectWithUnionQuery() = default;
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Block InterpreterSelectWithUnionQuery::getSampleBlock()
{
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return result_header;
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}
Block InterpreterSelectWithUnionQuery::getSampleBlock(
const ASTPtr & query_ptr,
const Context & context)
{
auto & cache = context.getSampleBlockCache();
/// Using query string because query_ptr changes for every internal SELECT
auto key = queryToString(query_ptr);
if (cache.find(key) != cache.end())
{
return cache[key];
}
return cache[key] = InterpreterSelectWithUnionQuery(query_ptr, context, {}, QueryProcessingStage::Complete, 0, true).getSampleBlock();
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}
BlockInputStreams InterpreterSelectWithUnionQuery::executeWithMultipleStreams()
{
BlockInputStreams nested_streams;
for (auto & interpreter : nested_interpreters)
{
BlockInputStreams streams = interpreter->executeWithMultipleStreams();
nested_streams.insert(nested_streams.end(), streams.begin(), streams.end());
}
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/// Unify data structure.
if (nested_interpreters.size() > 1)
for (auto & stream : nested_streams)
stream = std::make_shared<ConvertingBlockInputStream>(context, stream, result_header, ConvertingBlockInputStream::MatchColumnsMode::Position);
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return nested_streams;
}
BlockIO InterpreterSelectWithUnionQuery::execute()
{
const Settings & settings = context.getSettingsRef();
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BlockInputStreams nested_streams = executeWithMultipleStreams();
BlockInputStreamPtr result_stream;
if (nested_streams.empty())
{
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result_stream = std::make_shared<NullBlockInputStream>(getSampleBlock());
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}
else if (nested_streams.size() == 1)
{
result_stream = nested_streams.front();
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nested_streams.clear();
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}
else
{
result_stream = std::make_shared<UnionBlockInputStream<>>(nested_streams, nullptr, settings.max_threads);
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nested_streams.clear();
}
BlockIO res;
res.in = result_stream;
return res;
}
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void InterpreterSelectWithUnionQuery::ignoreWithTotals()
{
for (auto & interpreter : nested_interpreters)
interpreter->ignoreWithTotals();
}
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}