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Better coalesce [#CLICKHOUSE-2789].

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This commit is contained in:
Alexey Milovidov 2017-03-09 23:39:20 +03:00
parent 1abf959722
commit abe0fca1a4
1 changed files with 99 additions and 32 deletions
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123
dbms/src/Functions/FunctionsNull.cpp
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@ -114,6 +114,14 @@ void FunctionIsNotNull::executeImpl(Block & block, const ColumnNumbers & argumen
/// Implementation of coalesce.
static const DataTypePtr getNestedDataType(const DataTypePtr & type)
{
if (type->isNullable())
return static_cast<const DataTypeNullable &>(*type).getNestedType();
return type;
}
FunctionPtr FunctionCoalesce::create(const Context & context)
{
return std::make_shared<FunctionCoalesce>();
@ -131,52 +139,120 @@ bool FunctionCoalesce::hasSpecialSupportForNulls() const
DataTypePtr FunctionCoalesce::getReturnTypeImpl(const DataTypes & arguments) const
{
/// Skip all NULL arguments. If any argument is non-Nullable, skip all next arguments.
DataTypes filtered_args;
filtered_args.reserve(arguments.size());
for (const auto & arg : arguments)
{
if (arg->isNull())
continue;
filtered_args.push_back(arg);
if (!arg->isNullable())
break;
}
DataTypes new_args;
for (size_t i = 0; i < arguments.size(); ++i)
for (size_t i = 0; i < filtered_args.size(); ++i)
{
bool is_last = i + 1 == filtered_args.size();
if (is_last)
{
new_args.push_back(filtered_args[i]);
}
else
{
new_args.push_back(std::make_shared<DataTypeUInt8>());
new_args.push_back(arguments[i]);
new_args.push_back(getNestedDataType(filtered_args[i]));
}
}
new_args.push_back(std::make_shared<DataTypeNull>());
return FunctionMultiIf{}.getReturnTypeImpl(new_args);
if (new_args.empty())
return std::make_shared<DataTypeNull>();
if (new_args.size() == 1)
return new_args.front();
auto res = FunctionMultiIf{}.getReturnTypeImpl(new_args);
/// if last argument is not nullable, result should be also not nullable
if (!new_args.back()->isNullable() && res->isNullable())
res = getNestedDataType(res);
return res;
}
void FunctionCoalesce::executeImpl(Block & block, const ColumnNumbers & arguments, size_t result)
{
/// coalesce(arg0, arg1, ..., argN) is essentially
/// multiIf(isNotNull(arg0), arg0, isNotNull(arg1), arg1, ..., isNotNull(argN), argN, NULL)
/// multiIf(isNotNull(arg0), assumeNotNull(arg0), isNotNull(arg1), assumeNotNull(arg1), ..., argN)
/// with constant NULL arguments removed.
ColumnNumbers filtered_args;
filtered_args.reserve(arguments.size());
for (const auto & arg : arguments)
{
const auto & column = block.getByPosition(arg).column;
if (column->isNull())
continue;
filtered_args.push_back(arg);
if (!column->isNullable())
break;
}
FunctionIsNotNull is_not_null;
FunctionAssumeNotNull assume_not_null;
ColumnNumbers multi_if_args;
Block temp_block = block;
for (size_t i = 0; i < arguments.size(); ++i)
for (size_t i = 0; i < filtered_args.size(); ++i)
{
size_t res_pos = temp_block.columns();
temp_block.insert({nullptr, std::make_shared<DataTypeUInt8>(), ""});
bool is_last = i + 1 == filtered_args.size();
is_not_null.executeImpl(temp_block, {arguments[i]}, res_pos);
if (is_last)
{
multi_if_args.push_back(filtered_args[i]);
}
else
{
temp_block.insert({nullptr, std::make_shared<DataTypeUInt8>(), ""});
is_not_null.executeImpl(temp_block, {filtered_args[i]}, res_pos);
temp_block.insert({nullptr, getNestedDataType(block.getByPosition(filtered_args[i]).type), ""});
assume_not_null.executeImpl(temp_block, {filtered_args[i]}, res_pos + 1);
multi_if_args.push_back(res_pos);
multi_if_args.push_back(arguments[i]);
multi_if_args.push_back(res_pos + 1);
}
}
/// Argument corresponding to the fallback NULL value.
multi_if_args.push_back(temp_block.columns());
/// If all arguments appeared to be NULL.
if (multi_if_args.empty())
{
block.getByPosition(result).column = std::make_shared<ColumnNull>(block.rows(), Null());
return;
}
/// Append a fallback NULL column.
ColumnWithTypeAndName elem;
elem.column = std::make_shared<ColumnNull>(temp_block.rows(), Null());
elem.type = std::make_shared<DataTypeNull>();
elem.name = "NULL";
temp_block.insert(elem);
if (multi_if_args.size() == 1)
{
block.getByPosition(result).column = block.getByPosition(multi_if_args.front()).column;
return;
}
FunctionMultiIf{}.executeImpl(temp_block, multi_if_args, result);
block.safeGetByPosition(result).column = std::move(temp_block.safeGetByPosition(result).column);
auto res = std::move(temp_block.safeGetByPosition(result).column);
/// if last argument is not nullable, result should be also not nullable
if (!block.getByPosition(multi_if_args.back()).column->isNullable() && res->isNullable())
res = static_cast<ColumnNullable &>(*res).getNestedColumn();
block.safeGetByPosition(result).column = res;
}
/// Implementation of ifNull.
@ -191,15 +267,6 @@ std::string FunctionIfNull::getName() const
return name;
}
static const DataTypePtr getNestedDataType(const DataTypePtr & type)
{
if (type->isNullable())
return static_cast<const DataTypeNullable &>(*type).getNestedType();
return type;
}
bool FunctionIfNull::hasSpecialSupportForNulls() const
{
return true;