/// Construct a conjunction from given functions
static ASTPtr buildWhereExpression(const ASTs & functions)
{
if (functions.size() == 0)
return nullptr;
if (functions.size() == 1)
return functions[0];
ASTPtr new_query = std::make_shared<ASTFunction>();
ASTFunction & new_function = typeid_cast<ASTFunction & >(*new_query);
new_function.name = "and";
new_function.arguments = std::make_shared<ASTExpressionList>();
new_function.arguments->children = functions;
new_function.children.push_back(new_function.arguments);
return new_query;
}
bool ParserCase::parseImpl(Pos & pos, Pos end, ASTPtr & node, Pos & max_parsed_pos, Expected & expected)
{
Pos begin = pos;
ParserWhiteSpaceOrComments ws;
ParserString s_case{"CASE", true, true};
ParserString s_when{"WHEN", true, true};
ParserString s_then{"THEN", true, true};
ParserString s_else{"ELSE", true, true};
ParserString s_end{ "END", true, true};
ParserExpressionWithOptionalAlias p_expr{false};
if (!s_case.parse(pos, end, node, max_parsed_pos, expected))
{
/// Parse as a simple ASTFunction.
return ParserFunction{}.parse(pos = begin, end, node, max_parsed_pos, expected);
}
ws.ignore(pos, end);
bool has_case_expr = false;
auto old_pos = pos;
has_case_expr = !s_when.parse(pos, end, node, max_parsed_pos, expected);
pos = old_pos;
ASTs args;
auto parse_branches = [&]()
{
bool has_branch = false;
while (s_when.parse(pos, end, node, max_parsed_pos, expected))
{
has_branch = true;
ws.ignore(pos, end);
ASTPtr expr_when;
if (!p_expr.parse(pos, end, expr_when, max_parsed_pos, expected))
return false;
args.push_back(expr_when);
ws.ignore(pos, end);
if (!s_then.parse(pos, end, node, max_parsed_pos, expected))
return false;
ws.ignore(pos, end);
ASTPtr expr_then;
if (!p_expr.parse(pos, end, expr_then, max_parsed_pos, expected))
return false;
args.push_back(expr_then);
ws.ignore(pos, end);
}
if (!has_branch)
return false;
ws.ignore(pos, end);
if (!s_else.parse(pos, end, node, max_parsed_pos, expected))
return false;
ws.ignore(pos, end);
ASTPtr expr_else;
if (!p_expr.parse(pos, end, expr_else, max_parsed_pos, expected))
return false;
args.push_back(expr_else);
ws.ignore(pos, end);
if (!s_end.parse(pos, end, node, max_parsed_pos, expected))
return false;
return true;
};
if (has_case_expr)
{
ASTPtr case_expr;
if (!p_expr.parse(pos, end, case_expr, max_parsed_pos, expected))
return false;
args.push_back(case_expr);
ws.ignore(pos, end);
if (!parse_branches())
return false;
auto function_args = std::make_shared<ASTExpressionList>(StringRange{begin, pos});
function_args->children = std::move(args);
auto function = std::make_shared<ASTFunction>(StringRange{begin, pos});
function->name = "caseWithExpr";
function->arguments = function_args;
function->children.push_back(function->arguments);
node = function;
}
else
{
if (!parse_branches())
return false;
auto function_args = std::make_shared<ASTExpressionList>(StringRange{begin, pos});
function_args->children = std::move(args);
auto function = std::make_shared<ASTFunction>(StringRange{begin, pos});
function->name = "caseWithoutExpr";
function->arguments = function_args;
function->children.push_back(function->arguments);
node = function;
}
return true;
}
bool ParserCase::parseImpl(Pos & pos, ASTPtr & node, Expected & expected)
{
ParserKeyword s_case{"CASE"};
ParserKeyword s_when{"WHEN"};
ParserKeyword s_then{"THEN"};
ParserKeyword s_else{"ELSE"};
ParserKeyword s_end{ "END"};
ParserExpressionWithOptionalAlias p_expr{false};
if (!s_case.ignore(pos, expected))
return false;
auto old_pos = pos;
bool has_case_expr = !s_when.ignore(pos, expected);
pos = old_pos;
ASTs args;
auto parse_branches = [&]()
{
bool has_branch = false;
while (s_when.ignore(pos, expected))
{
has_branch = true;
ASTPtr expr_when;
if (!p_expr.parse(pos, expr_when, expected))
return false;
args.push_back(expr_when);
if (!s_then.ignore(pos, expected))
return false;
ASTPtr expr_then;
if (!p_expr.parse(pos, expr_then, expected))
return false;
args.push_back(expr_then);
}
if (!has_branch)
return false;
ASTPtr expr_else;
if (s_else.ignore(pos, expected))
{
if (!p_expr.parse(pos, expr_else, expected))
return false;
}
else
{
Field field_with_null;
ASTLiteral null_literal(field_with_null);
expr_else = std::make_shared<ASTLiteral>(null_literal);
}
args.push_back(expr_else);
if (!s_end.ignore(pos, expected))
return false;
return true;
};
if (has_case_expr)
{
ASTPtr case_expr;
if (!p_expr.parse(pos, case_expr, expected))
return false;
args.push_back(case_expr);
if (!parse_branches())
return false;
auto function_args = std::make_shared<ASTExpressionList>();
function_args->children = std::move(args);
auto function = std::make_shared<ASTFunction>();
function->name = "caseWithExpression";
function->arguments = function_args;
function->children.push_back(function->arguments);
node = function;
}
else
{
if (!parse_branches())
return false;
auto function_args = std::make_shared<ASTExpressionList>();
function_args->children = std::move(args);
auto function = std::make_shared<ASTFunction>();
function->name = "multiIf";
function->arguments = function_args;
function->children.push_back(function->arguments);
node = function;
}
return true;
}
