Function makeUniqueColumnNamesInBlock

src/Analyzer/Utils.cpp:197–224

}

void makeUniqueColumnNamesInBlock(Block & block)
{
    NameSet block_column_names;
    size_t unique_column_name_counter = 1;

    for (auto & column_with_type : block)
    {
        if (block_column_names.insert(column_with_type.name).second)
            continue;

        /// The base name collides with a name we have already kept or produced.
        /// Loop until we find a suffix that is unused anywhere in the block,
        /// including by names we are about to keep and by names we have already
        /// renamed. Register the renamed name to prevent further collisions.
        ///
        /// Example: for input `a, a, a_1`, the second `a` is renamed to `a_1`
        /// and the third column (`a_1`) is renamed to `a_2`, instead of leaving
        /// the block with two `a_1` columns.
        String new_name;
        do
        {
            new_name = column_with_type.name + '_' + std::to_string(unique_column_name_counter);
            ++unique_column_name_counter;
        } while (!block_column_names.insert(new_name).second);

        column_with_type.name = std::move(new_name);
    }
}

bool isExpressionNodeType(QueryTreeNodeType node_type)
{