CRT-P0001 · Multiple `append` can be combined into a single call

Multiple append can be combined into a single call CRT-P0001

Performance

Major

4 months ago — 4 years old

can combine chain of 4 appends into one

155				resourceTypes = append(resourceTypes, t.Type)
156			}
157
158			row = append(row, stringOrDefault(w.GardenAddr))159			row = append(row, stringOrDefault(w.BaggageclaimURL))
160			row = append(row, stringOrDefault(strconv.Itoa(w.ActiveTasks)))
161			row = append(row, stringOrDefault(strings.Join(resourceTypes, ", ")))

can combine chain of 2 appends into one

fly/commands/teams.go

 86					groupsCell.Color = color.New(color.Faint)
 87				}
 88
 89				row = append(row, usersCell) 90				row = append(row, groupsCell)
 91				table.Data = append(table.Data, row)
 92			}

can combine chain of 2 appends into one

fly/commands/pipelines.go

 89		if command.All {
 90			row = append(row, ui.TableCell{Contents: p.TeamName})
 91		}
 92		row = append(row, pausedColumn) 93		row = append(row, publicColumn)
 94		if command.IncludeArchived {
 95			row = append(row, archivedColumn)

can combine chain of 2 appends into one

fly/commands/pipelines.go

 84		}
 85
 86		row := ui.TableRow{}
 87		row = append(row, ui.TableCell{Contents: strconv.Itoa(p.ID)}) 88		row = append(row, ui.TableCell{Contents: p.Ref().String()})
 89		if command.All {
 90			row = append(row, ui.TableCell{Contents: p.TeamName})

can combine chain of 3 appends into one

fly/commands/paused_pipelines.go

 95			row = append(row, ui.TableCell{Contents: p.TeamName})
 96		}
 97
 98		row = append(row, pausedColumn) 99		row = append(row, pausedByColumn)
100		row = append(row, pausedAtColumn)
101		table.Data = append(table.Data, row)

Description

Multiple calls for append could be combined into a single call for append.

The append built-in function appends elements to the end of a slice. If it has sufficient capacity, the destination is resliced to accommodate the new elements, but if capacity is not enough, then append will allocate a new underlying array and return the updated slice. Therefore, it is necessary to store the result of append, often in the variable holding the slice itself. Appending calls in a single call of append allocates memory just once to accommodate all the elements to be appended. Whereas multiple calls to append introduce many overheads, most notably being the possibility of more calls for memory allocation because the total number of elements to be appended over multiple calls of append is unknown beforehand, resulting in inaccurate preallocation.

Read more about a similar implementation for append. Hence, a single call to append is recommended.

Bad practice

xs = append(xs, 1)
xs = append(xs, 2)
xs = append(xs, 3)
xs = append(xs, 4)
xs = append(xs, 5)

concourse / concourse

Bad practice

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