Function getArrayJoinedColumns

src/Interpreters/TreeRewriter.cpp:655–700

}

void getArrayJoinedColumns(ASTPtr & query, TreeRewriterResult & result, const ASTSelectQuery * select_query,
                           const NamesAndTypesList & source_columns, const NameSet & source_columns_set)
{
    if (ASTPtr array_join_expression_list = select_query->arrayJoinExpressionList())
    {
        ArrayJoinedColumnsVisitor::Data visitor_data{result.aliases,
                                                    result.array_join_name_to_alias,
                                                    result.array_join_alias_to_name,
                                                    result.array_join_result_to_source};
        ArrayJoinedColumnsVisitor(visitor_data).visit(query);

        /// If the result of ARRAY JOIN is not used, it is necessary to ARRAY-JOIN any column,
        /// to get the correct number of rows.
        if (result.array_join_result_to_source.empty())
        {
            if (select_query->arrayJoinExpressionList()->children.empty())
                throw DB::Exception("ARRAY JOIN requires an argument", ErrorCodes::NUMBER_OF_ARGUMENTS_DOESNT_MATCH);

            ASTPtr expr = select_query->arrayJoinExpressionList()->children.at(0);
            String source_name = expr->getColumnName();
            String result_name = expr->getAliasOrColumnName();

            /// This is an array.
            if (!expr->as<ASTIdentifier>() || source_columns_set.count(source_name))
            {
                result.array_join_result_to_source[result_name] = source_name;
            }
            else /// This is a nested table.
            {
                bool found = false;
                for (const auto & column : source_columns)
                {
                    auto split = Nested::splitName(column.name);
                    if (split.first == source_name && !split.second.empty())
                    {
                        result.array_join_result_to_source[Nested::concatenateName(result_name, split.second)] = column.name;
                        found = true;
                        break;
                    }
                }
                if (!found)
                    throw Exception("No columns in nested table " + source_name, ErrorCodes::EMPTY_NESTED_TABLE);
            }
        }
    }
}

void setJoinStrictness(ASTSelectQuery & select_query, JoinStrictness join_default_strictness, bool old_any, ASTTableJoin & out_table_join)
{