mirror of
https://github.com/ClickHouse/ClickHouse.git
synced 2024-11-18 05:32:52 +00:00
109 lines
3.5 KiB
C++
109 lines
3.5 KiB
C++
#include <Common/typeid_cast.h>
|
|
#include <Parsers/ASTLiteral.h>
|
|
#include <Parsers/ASTFunction.h>
|
|
#include <Parsers/ASTExpressionList.h>
|
|
#include <Interpreters/OptimizeIfWithConstantConditionVisitor.h>
|
|
#include <IO/WriteHelpers.h>
|
|
|
|
namespace DB
|
|
{
|
|
|
|
namespace ErrorCodes
|
|
{
|
|
extern const int NUMBER_OF_ARGUMENTS_DOESNT_MATCH;
|
|
}
|
|
|
|
static bool tryExtractConstValueFromCondition(const ASTPtr & condition, bool & value)
|
|
{
|
|
/// numeric constant in condition
|
|
if (const auto * literal = condition->as<ASTLiteral>())
|
|
{
|
|
if (literal->value.getType() == Field::Types::Int64 ||
|
|
literal->value.getType() == Field::Types::UInt64)
|
|
{
|
|
value = literal->value.get<Int64>();
|
|
return true;
|
|
}
|
|
}
|
|
|
|
/// cast of numeric constant in condition to UInt8
|
|
if (const auto * function = condition->as<ASTFunction>())
|
|
{
|
|
if (function->name == "CAST")
|
|
{
|
|
if (const auto * expr_list = function->arguments->as<ASTExpressionList>())
|
|
{
|
|
const ASTPtr & type_ast = expr_list->children.at(1);
|
|
if (const auto * type_literal = type_ast->as<ASTLiteral>())
|
|
{
|
|
if (type_literal->value.getType() == Field::Types::String &&
|
|
type_literal->value.get<std::string>() == "UInt8")
|
|
return tryExtractConstValueFromCondition(expr_list->children.at(0), value);
|
|
}
|
|
}
|
|
}
|
|
}
|
|
|
|
return false;
|
|
}
|
|
|
|
void OptimizeIfWithConstantConditionVisitor::visit(ASTPtr & current_ast)
|
|
{
|
|
if (!current_ast)
|
|
return;
|
|
|
|
for (ASTPtr & child : current_ast->children)
|
|
{
|
|
auto * function_node = child->as<ASTFunction>();
|
|
if (!function_node || function_node->name != "if")
|
|
{
|
|
visit(child);
|
|
continue;
|
|
}
|
|
|
|
visit(function_node->arguments);
|
|
const auto * args = function_node->arguments->as<ASTExpressionList>();
|
|
|
|
if (args->children.size() != 3)
|
|
throw Exception("Wrong number of arguments for function 'if' (" + toString(args->children.size()) + " instead of 3)",
|
|
ErrorCodes::NUMBER_OF_ARGUMENTS_DOESNT_MATCH);
|
|
|
|
ASTPtr condition_expr = args->children[0];
|
|
ASTPtr then_expr = args->children[1];
|
|
ASTPtr else_expr = args->children[2];
|
|
|
|
bool condition;
|
|
if (tryExtractConstValueFromCondition(condition_expr, condition))
|
|
{
|
|
ASTPtr replace_ast = condition ? then_expr : else_expr;
|
|
ASTPtr child_copy = child;
|
|
String replace_alias = replace_ast->tryGetAlias();
|
|
String if_alias = child->tryGetAlias();
|
|
|
|
if (replace_alias.empty())
|
|
{
|
|
replace_ast->setAlias(if_alias);
|
|
child = replace_ast;
|
|
}
|
|
else
|
|
{
|
|
/// Only copy of one node is required here.
|
|
/// But IAST has only method for deep copy of subtree.
|
|
/// This can be a reason of performance degradation in case of deep queries.
|
|
ASTPtr replace_ast_deep_copy = replace_ast->clone();
|
|
replace_ast_deep_copy->setAlias(if_alias);
|
|
child = replace_ast_deep_copy;
|
|
}
|
|
|
|
if (!if_alias.empty())
|
|
{
|
|
auto alias_it = aliases.find(if_alias);
|
|
if (alias_it != aliases.end() && alias_it->second.get() == child_copy.get())
|
|
alias_it->second = child;
|
|
}
|
|
}
|
|
}
|
|
}
|
|
|
|
}
|