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#pragma once
#include <Interpreters/InDepthNodeVisitor.h>
#include <Parsers/ASTFunction.h>
#include <Parsers/ASTOrderByElement.h>
#include <Parsers/ASTExpressionList.h>
#include <Parsers/ASTIdentifier.h>
#include <Functions/FunctionFactory.h>
namespace DB
{
class ASTIdentifier;
class RedundantFunctionsInOrderByMatcher
{
public:
struct Data
{
std::unordered_set<String> & keys;
ContextPtr context;
bool redundant = true;
bool done = false;
void preventErase()
{
redundant = false;
done = true;
}
};
static void visit(const ASTPtr & ast, Data & data)
{
if (const auto * func = ast->as<ASTFunction>())
visit(*func, data);
}
static void visit(const ASTFunction & ast_function, Data & data)
{
if (data.done)
return;
bool is_lambda = (ast_function.name == "lambda");
const auto & arguments = ast_function.arguments;
bool has_arguments = arguments && !arguments->children.empty();
if (is_lambda || !has_arguments)
{
data.preventErase();
return;
}
/// If we meet function as argument then we have already checked
/// arguments of it and if it can be erased
for (const auto & arg : arguments->children)
{
/// Allow functions: visit them later
if (arg->as<ASTFunction>())
continue;
/// Allow known identifiers: they are present in ORDER BY before current item
if (auto * identifier = arg->as<ASTIdentifier>())
if (data.keys.count(getIdentifierName(identifier)))
continue;
/// Reject erase others
data.preventErase();
return;
}
const auto function = FunctionFactory::instance().tryGet(ast_function.name, data.context);
if (!function || !function->isDeterministicInScopeOfQuery())
{
data.preventErase();
}
}
static bool needChildVisit(const ASTPtr & node, const ASTPtr &)
{
/// Visit functions and their arguments, that are stored in ASTExpressionList.
return node->as<ASTFunction>() || node->as<ASTExpressionList>();
}
};
using RedundantFunctionsInOrderByVisitor = ConstInDepthNodeVisitor<RedundantFunctionsInOrderByMatcher, true>;
}
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