ClickHouse/src/Interpreters/RemoveInjectiveFunctionsVisitor.cpp
2021-06-01 15:20:52 +03:00

65 lines
1.8 KiB
C++

#include <Common/typeid_cast.h>
#include <Parsers/ASTSubquery.h>
#include <Parsers/ASTFunction.h>
#include <Parsers/ASTTablesInSelectQuery.h>
#include <Interpreters/RemoveInjectiveFunctionsVisitor.h>
#include <AggregateFunctions/AggregateFunctionFactory.h>
#include <Functions/FunctionFactory.h>
namespace DB
{
static bool isUniq(const ASTFunction & func)
{
return func.name == "uniq" || func.name == "uniqExact" || func.name == "uniqHLL12"
|| func.name == "uniqCombined" || func.name == "uniqCombined64"
|| func.name == "uniqTheta";
}
/// Remove injective functions of one argument: replace with a child
static bool removeInjectiveFunction(ASTPtr & ast, ContextPtr context, const FunctionFactory & function_factory)
{
const ASTFunction * func = ast->as<ASTFunction>();
if (!func)
return false;
if (!func->arguments || func->arguments->children.size() != 1)
return false;
if (!function_factory.get(func->name, context)->isInjective({}))
return false;
ast = func->arguments->children[0];
return true;
}
void RemoveInjectiveFunctionsMatcher::visit(ASTPtr & ast, const Data & data)
{
if (auto * func = ast->as<ASTFunction>())
visit(*func, ast, data);
}
void RemoveInjectiveFunctionsMatcher::visit(ASTFunction & func, ASTPtr &, const Data & data)
{
if (isUniq(func))
{
const FunctionFactory & function_factory = FunctionFactory::instance();
for (auto & arg : func.arguments->children)
{
while (removeInjectiveFunction(arg, data.getContext(), function_factory))
;
}
}
}
bool RemoveInjectiveFunctionsMatcher::needChildVisit(const ASTPtr & node, const ASTPtr &)
{
if (node->as<ASTSubquery>() ||
node->as<ASTTableExpression>())
return false; // NOLINT
return true;
}
}