Method getSelectResponse

engine/engine.go:95–149

getSelectResponse - Returns Select response basing on ast.OrderByCommand and ast.WhereCommand included in this Select

(selectCommand *ast.SelectCommand)

// getSelectResponse - Returns Select response basing on ast.OrderByCommand and ast.WhereCommand included in this Select
func (engine *DbEngine) getSelectResponse(selectCommand *ast.SelectCommand) (*Table, error) {
	var table *Table
	var err error

	if selectCommand.HasJoinCommand() {
		joinCommand := selectCommand.JoinCommand
		table, err = engine.joinTables(joinCommand, selectCommand.Name.Token.Literal)
		if err != nil {
			return nil, err
		}
	} else {
		var exist bool
		table, exist = engine.Tables[selectCommand.Name.Token.Literal]

		if !exist {
			return nil, &TableDoesNotExistError{selectCommand.Name.Token.Literal}
		}
	}

	if selectCommand.HasWhereCommand() {
		whereCommand := selectCommand.WhereCommand
		if selectCommand.HasOrderByCommand() {
			orderByCommand := selectCommand.OrderByCommand
			table, err = engine.selectFromTableWithWhereAndOrderBy(selectCommand, whereCommand, orderByCommand, table)
			if err != nil {
				return nil, err
			}
		} else {
			table, err = engine.selectFromTableWithWhere(selectCommand, whereCommand, table)
			if err != nil {
				return nil, err
			}
		}
	} else if selectCommand.HasOrderByCommand() {
		table, err = engine.selectFromTableWithOrderBy(selectCommand, selectCommand.OrderByCommand, table)
		if err != nil {
			return nil, err
		}
	} else {
		table, err = engine.selectFromProvidedTable(selectCommand, table)
		if err != nil {
			return nil, err
		}
	}

	if selectCommand.HasLimitCommand() || selectCommand.HasOffsetCommand() {
		table.applyOffsetAndLimit(selectCommand)
	}

	if selectCommand.HasDistinct {
		table = table.getDistinctTable()
	}

	return table, nil
}

// createTable - initialize new table in engine with specified name
func (engine *DbEngine) createTable(command *ast.CreateCommand) error {