Function parseGroupByExpression

engine/src/operators/GroupBy.cpp:140–181

}

std::tuple<std::vector<int>, std::vector<std::string>, std::vector<AggregateKind>,std::vector<std::string>>
	parseGroupByExpression(const std::string & queryString, std::size_t num_cols){
	std::vector<AggregateKind> aggregation_types;
	std::vector<std::string> aggregation_input_expressions;
	std::vector<int> group_column_indices;

	// Get aggregations
	std::vector<std::string> aggregation_expressions;
	std::vector<std::string> aggregation_column_assigned_aliases;

	auto rangeStart = queryString.find("(");
	auto rangeEnd = queryString.rfind(")") - rangeStart;
	std::string combined_expression = queryString.substr(rangeStart + 1, rangeEnd - 1);

	// in case UNION exists,
	if (combined_expression == "group=[{*}]") {
		StringUtil::findAndReplaceAll(combined_expression, "*", StringUtil::makeCommaDelimitedSequence(num_cols));
	}

	group_column_indices = get_group_columns(combined_expression);
	std::vector<std::string> expressions = get_expressions_from_expression_list(combined_expression);
	for(std::string expr : expressions) {
		std::string expression = std::regex_replace(expr, std::regex("^ +| +$|( ) +"), "$1");
		if(expression.find("group=") == std::string::npos) {
			aggregation_expressions.push_back(expression);

			// if the aggregation has an alias, lets capture it here, otherwise we'll figure out what to call the
			// aggregation based on its input
			if(expression.find("EXPR$") == 0)
				aggregation_column_assigned_aliases.push_back("");
			else
				aggregation_column_assigned_aliases.push_back(expression.substr(0, expression.find("=[")));
		}
	}

	for(std::string expression : aggregation_expressions) {
		aggregation_types.push_back(get_aggregation_operation(expression));
		aggregation_input_expressions.push_back(get_string_between_outer_parentheses(expression));
	}
	return std::make_tuple(std::move(group_column_indices), std::move(aggregation_input_expressions),
		std::move(aggregation_types), std::move(aggregation_column_assigned_aliases));
}

std::tuple<std::vector<int>, std::vector<std::string>, std::vector<AggregateKind>,	std::vector<std::string>>
	modGroupByParametersPostComputeAggregations(const std::vector<int> & group_column_indices,