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Simplify the logic by just adding ORDER BY list to SELECT

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This commit is contained in:
Alexander Gololobov 2022-11-12 12:58:53 +01:00
parent 0e031f93e9
commit 4ad8e2974d
1 changed files with 14 additions and 61 deletions
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75
src/Parsers/ASTProjectionSelectQuery.cpp
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@ -119,64 +119,6 @@ ASTPtr & ASTProjectionSelectQuery::getExpression(Expression expr)
return children[positions[expr]];
}
namespace
{
ASTPtr wrapAsOrderByElement(const ASTPtr & expr)
{
auto elem = std::make_shared<ASTOrderByElement>();
elem->direction = 1; /// Currently it cannot be specified in projection definition so it is ASC default
elem->nulls_direction = elem->direction;
elem->nulls_direction_was_explicitly_specified = false;
elem->with_fill = false;
elem->children.push_back(expr);
return elem;
}
/// Currently the ORDER BY clause in projection definition is parsed differently from ORDER BY of a standalone SELECT query.
/// This function converts this simplified AST into AST compatible with SELECT query.
/// If ORDER BY clause has single element then simple_order_by represents this element,
/// otherwise simple_order_by is a function "tuple" of all elements.
ASTPtr cloneToOrderByASTForSelect(const ASTPtr & simple_order_by)
{
ASTPtr expression_list = std::make_shared<ASTExpressionList>();
if (simple_order_by->children.empty())
{
expression_list->children.emplace_back(wrapAsOrderByElement(simple_order_by->clone()));
}
else
{
auto * func = simple_order_by->as<ASTFunction>();
if (!func || func->name != "tuple")
{
expression_list->children.emplace_back(wrapAsOrderByElement(func->clone()));
}
else
{
if (func->children.size() != 1)
throw Exception(ErrorCodes::LOGICAL_ERROR,
"Unexpected structure of ORDER BY clause in projection definition {}",
func->dumpTree(0));
auto * params = func->children[0]->as<ASTExpressionList>();
if (!params)
throw Exception(ErrorCodes::LOGICAL_ERROR,
"Unexpected structure of ORDER BY clause in projection definition {}; Expression list expected",
func->dumpTree(0));
for (auto & child : params->children)
{
expression_list->children.emplace_back(wrapAsOrderByElement(child->clone()));
}
}
}
return expression_list;
}
}
ASTPtr ASTProjectionSelectQuery::cloneToASTSelect() const
{
auto select_query = std::make_shared<ASTSelectQuery>();
@ -184,11 +126,22 @@ ASTPtr ASTProjectionSelectQuery::cloneToASTSelect() const
if (with())
select_query->setExpression(ASTSelectQuery::Expression::WITH, with()->clone());
if (select())
select_query->setExpression(ASTSelectQuery::Expression::SELECT, select()->clone());
{
ASTPtr select_list = select()->clone();
if (orderBy())
{
/// Add ORDER BY list to SELECT for simplicity. It is Ok because we only uses this to find all required columns.
auto * expressions = select_list->as<ASTExpressionList>();
if (!expressions)
throw Exception(ErrorCodes::LOGICAL_ERROR,
"Unexpected structure of SELECT clause in projection definition {}; Expression list expected",
select_list->dumpTree(0));
expressions->children.emplace_back(orderBy()->clone());
}
select_query->setExpression(ASTSelectQuery::Expression::SELECT, std::move(select_list));
}
if (groupBy())
select_query->setExpression(ASTSelectQuery::Expression::GROUP_BY, groupBy()->clone());
if (orderBy())
select_query->setExpression(ASTSelectQuery::Expression::ORDER_BY, cloneToOrderByASTForSelect(orderBy()));
return node;
}