{

const ColumnUInt8 * column_filter = typeid_cast<const ColumnUInt8 *>(&*mapped);

if (!column_filter)

{

const auto * column_filter_const = checkAndGetColumnConst<ColumnUInt8>(&*mapped);

if (!column_filter_const)

throw Exception(ErrorCodes::ILLEGAL_COLUMN, "Unexpected type of filter column: {}; The result of the lambda is expected to be a UInt8", mapped->getDataType());

if (column_filter_const->getValue<UInt8>())

return array.clone();

return ColumnArray::create(array.getDataPtr()->cloneEmpty(), ColumnArray::ColumnOffsets::create(array.size(), 0));

}

const IColumn::Filter & filter = column_filter->getData();

ColumnPtr filtered = array.getData().filter(filter, -1);

const IColumn::Offsets & in_offsets = array.getOffsets();

auto column_offsets = ColumnArray::ColumnOffsets::create(in_offsets.size());

IColumn::Offsets & out_offsets = column_offsets->getData();

size_t in_pos = 0;

size_t out_pos = 0;

for (size_t i = 0; i < in_offsets.size(); ++i)

{

for (; in_pos < in_offsets[i]; ++in_pos)

{

if (filter[in_pos])

++out_pos;

}

out_offsets[i] = out_pos;

}

return ColumnArray::create(filtered, std::move(column_offsets));

{

FunctionDocumentation::Description description = "Returns an array containing only the elements in the source array for which a lambda function returns true.";

FunctionDocumentation::Syntax syntax = "arrayFilter(func(x[, y1, ..., yN]), source_arr[, cond1_arr, ... , condN_arr])]";

FunctionDocumentation::Arguments arguments = {

{"func(x[, y1, ..., yN])", "A lambda function which operates on elements of the source array (`x`) and condition arrays (`y`).", {"Lambda function"}},

{"source_arr", "The source array to process.", {"Array(T)"}},

{"[, cond1_arr, ... , condN_arr]", "Optional. N condition arrays providing additional arguments to the lambda function.", {"Array(T)"}},

};

FunctionDocumentation::ReturnedValue returned_value = {"Returns a subset of the source array", {"Array(T)"}};

FunctionDocumentation::Examples examples = {

{"Example 1", "SELECT arrayFilter(x -> x LIKE '%World%', ['Hello', 'abc World']) AS res", "['abc World']"},

{"Example 2", R"(

)",

"[2]"}

};

FunctionDocumentation::IntroducedIn introduced_in = {1, 1};

FunctionDocumentation::Category category = FunctionDocumentation::Category::Array;

FunctionDocumentation documentation = {description, syntax, arguments, {}, returned_value, examples, introduced_in, category};

factory.registerFunction<FunctionArrayFilter>(documentation);