transforms

transforms

-- import "gopkg.in/Clever/optimus.v3/transforms"

Package transforms provides a set of transformation functions that can be applied to optimus.Tables.

For backwards-compatibility, there is a Pair transform and a Join transform.

Join is the same as Pair, except that it overwrites the fields in the left row with the fields from the right row.

In later versions, the Join transform will be removed and Pair will be renamed Join. The JoinType struct will also be removed in favor of the LeftJoin, OuterJoin, etc. functions used by Pair.

Usage

var (
	// LeftJoin keeps any row where a Row was found in the left Table.
	LeftJoin = mustHave("left")
	// RightJoin keeps any row where a Row was found in the right Table.
	RightJoin = mustHave("right")
	// InnerJoin keeps any row where a Row was found in both Tables.
	InnerJoin = mustHave("left", "right")
	// OuterJoin keeps all rows.
	OuterJoin = mustHave()
)

var JoinType = joinStruct{Left: joinType{0}, Inner: joinType{1}}

Left: Always add row from Left table, even if no corresponding rows found in Right table) Inner: Only add row from Left table if corresponding row(s) found in Right table)

func Concat

func Concat(tables ...optimus.Table) optimus.TransformFunc

Concat returns a TransformFunc that concatenates all the Rows in the input Tables, in order.

func Concurrently

func Concurrently(fn optimus.TransformFunc, concurrency int) optimus.TransformFunc

Concurrently returns a TransformFunc that applies the given TransformFunc a number of times concurrently, based on the supplied concurrency count.

func Each

func Each(fn func(optimus.Row) error) optimus.TransformFunc

Each returns a TransformFunc that makes no changes to the table, but calls the given function on every Row.

func Fieldmap

func Fieldmap(mappings map[string][]string) optimus.TransformFunc

Fieldmap returns a TransformFunc that applies a field mapping to every Row.

func GroupBy

func GroupBy(identifier RowIdentifier) optimus.TransformFunc

GroupBy returns a TransformFunc that returns Rows of Rows grouped by their identifier. The identifier must be comparable. Each output row is one group of rows. The output row has two fields: id, which is the identifier for that group, and rows, which is the slice of Rows that share that identifier. For example, one output row in a grouping by the "group" field might look like: optimus.Row{"id": "a", "rows": []optimus.Row{{"group": "a", "val": 2"}, {"group": "a", "val": 3}}}

func Join

func Join(rightTable optimus.Table, leftHeader string, rightHeader string, join joinType) optimus.TransformFunc

Join returns a TransformFunc that joins Rows with another table using the specified join type.

func Map

func Map(transform func(optimus.Row) (optimus.Row, error)) optimus.TransformFunc

Map returns a TransformFunc that transforms every row with the given function.

func Pair

func Pair(rightTable optimus.Table, leftID, rightID RowIdentifier, filterFn func(optimus.Row) (bool, error)) optimus.TransformFunc

Pair returns a TransformFunc that pairs all the elements in the table with another table, based on the given identifier functions and join type.

func Reduce

func Reduce(fn func(accum, item optimus.Row) error) optimus.TransformFunc

Reduce returns a TransformFunc that reduces all the Rows to a single Row.

func Select

func Select(filter func(optimus.Row) (bool, error)) optimus.TransformFunc

Select returns a TransformFunc that removes any rows that don't pass the filter.

func Sort

func Sort(less func(i, j optimus.Row) (bool, error)) optimus.TransformFunc

Sort takes in a function that reports whether the row i should sort before row j. It outputs the rows in sorted order. The sort is not guaranteed to be stable.

func StableSort

func StableSort(less func(i, j optimus.Row) (bool, error)) optimus.TransformFunc

StableSort takes in a function that reports whether the row i should sort before row j. It outputs the rows in stably sorted order.

func TableTransform

func TableTransform(transform func(optimus.Row, chan<- optimus.Row) error) optimus.TransformFunc

TableTransform returns a TransformFunc that applies the given transform function.

func Unique

func Unique(hash RowIdentifier) optimus.TransformFunc

Unique returns a TransformFunc that returns Rows that are unique, according to the specified hash. No order is guaranteed for the unique row which is returned.

func Valuemap

func Valuemap(mappings map[string]map[interface{}]interface{}) optimus.TransformFunc

Valuemap returns a TransformFunc that applies a value mapping to every Row.

type RowIdentifier

type RowIdentifier func(optimus.Row) (interface{}, error)

RowIdentifier takes in a row and returns something that uniquely identifies the Row.

func KeyIdentifier

func KeyIdentifier(key string) RowIdentifier

KeyIdentifier is a convenience function that returns a RowIdentifier that identifies the row based on the value of a key in the Row.