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#include <memory>
#include <Parsers/ASTFunction.h>
#include <Parsers/ASTProjectionSelectQuery.h>
#include <Parsers/CommonParsers.h>
#include <Parsers/ExpressionElementParsers.h>
#include <Parsers/ExpressionListParsers.h>
#include <Parsers/IParserBase.h>
#include <Parsers/ParserProjectionSelectQuery.h>
namespace DB
{
bool ParserProjectionSelectQuery::parseImpl(Pos & pos, ASTPtr & node, Expected & expected)
{
auto select_query = std::make_shared<ASTProjectionSelectQuery>();
node = select_query;
ParserKeyword s_with("WITH");
ParserKeyword s_select("SELECT");
ParserKeyword s_group_by("GROUP BY");
ParserKeyword s_order_by("ORDER BY");
ParserNotEmptyExpressionList exp_list_for_with_clause(false);
ParserNotEmptyExpressionList exp_list_for_select_clause(true); /// Allows aliases without AS keyword.
ParserExpression order_expression_p;
ASTPtr with_expression_list;
ASTPtr select_expression_list;
ASTPtr group_expression_list;
ASTPtr order_expression;
/// WITH expr list
{
if (s_with.ignore(pos, expected))
{
if (!exp_list_for_with_clause.parse(pos, with_expression_list, expected))
return false;
}
}
/// SELECT [DISTINCT] [TOP N [WITH TIES]] expr list
{
if (!s_select.ignore(pos, expected))
return false;
if (!exp_list_for_select_clause.parse(pos, select_expression_list, expected))
return false;
}
// If group by is specified, AggregatingMergeTree engine is used, and the group by keys are implied to be order by keys
if (s_group_by.ignore(pos, expected))
{
if (!ParserList(std::make_unique<ParserExpression>(), std::make_unique<ParserToken>(TokenType::Comma))
.parse(pos, group_expression_list, expected))
return false;
}
// ORDER BY needs to be an ASTFunction so that we can use it as a sorting key
if (s_order_by.ignore(pos, expected))
{
ASTPtr expr_list;
if (!ParserList(std::make_unique<ParserExpression>(), std::make_unique<ParserToken>(TokenType::Comma)).parse(pos, expr_list, expected))
return false;
if (expr_list->children.size() == 1)
{
order_expression = expr_list->children.front();
}
else
{
auto function_node = std::make_shared<ASTFunction>();
function_node->name = "tuple";
function_node->arguments = expr_list;
function_node->children.push_back(expr_list);
order_expression = function_node;
}
}
select_query->setExpression(ASTProjectionSelectQuery::Expression::WITH, std::move(with_expression_list));
select_query->setExpression(ASTProjectionSelectQuery::Expression::SELECT, std::move(select_expression_list));
select_query->setExpression(ASTProjectionSelectQuery::Expression::GROUP_BY, std::move(group_expression_list));
select_query->setExpression(ASTProjectionSelectQuery::Expression::ORDER_BY, std::move(order_expression));
return true;
}
}
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