Method updateOutputHeader

src/Processors/QueryPlan/InputSelectorStep.cpp:24–32

}

void InputSelectorStep::updateOutputHeader()
{
    if (!input_headers[0]->empty())
        throw Exception(ErrorCodes::LOGICAL_ERROR, "InputSelectorStep: signal header must be empty");

    assertBlocksHaveEqualStructure(*input_headers[1], *input_headers[2], "InputSelectorStep");

    output_header = input_headers[1];
}

/// If the pipeline header has extra columns not in the expected header, add an ExpressionTransform to drop them.
static void dropExtraColumns(QueryPipelineBuilder & pipeline, const Block & expected_header)