Package recmgr provides a thin, multi-keyed, goroutine-safe wrapper around Google's btree package. It facilitates the use of multiple indexes to manage an in-memory collection of records.

This package operates on pointers to values, typically structs that can be indexed in multiple ways.

The methods in this package correspond to the methods of the same name in the btree package. Because multiple indexes are processed as a group, some methods are not supported, for example DeleteMin() and DeleteMax(). Similarly, some method semantics are different, for example Delete() returns the number of removed keys rather than the deleted item. Additionally, variations of the traversal methods are available that return a slice of record pointers.

All methods in this package are safe for concurrent goroutine use.

Test coverage is 100%.

##Installation

To install and later update the package on your system, run

go get -u github.com/jung-kurt/recmgr

##Quick Start

The following Go code demonstrates the creation and operation of a record manager instance.

var grp recmgr.GrpType
type person struct {
	name string
	num  int
}
personList := []person{
	{"Athos", 1},
	{"Porthos", 2},
	{"Aramis", 3}}
idxName := grp.Index(4, func(a, b interface{}) bool {
	return a.(*person).name < b.(*person).name
})
idxNum := grp.Index(4, func(a, b interface{}) bool {
	return a.(*person).num < b.(*person).num
})
for j := range personList {
	grp.ReplaceOrInsert(&personList[j])
}
print := func(recPtr interface{}) bool {
	p := recPtr.(*person)
	fmt.Printf("    %-8s %2d\n", p.name, p.num)
	return true
}
fmt.Println("Name order")
idxName.Ascend(print)
fmt.Println("Number order")
idxNum.Ascend(print)
// Output:
// Name order
//     Aramis    3
//     Athos     1
//     Porthos   2
// Number order
//     Athos     1
//     Porthos   2
//     Aramis    3

##Limitations

The records managed by this package are referenced by pointers so they should remain accessible for the duration of the recmgr instance. Notice in the range loop shown above that the record address passed to ReplaceOrInsert() points into the array that underlies the personList slice, not the address of the range expression's ephemeral second value.

Within the managed collection of records, if any key field (that is, any struct field that is used in the less function passed to Index()) is modified, it is advised to delete the record before modification and add it again afterward to keep the underlying btrees consistent. Non-key fields can be changed with impunity.

##License

recmgr is copyrighted by Kurt Jung and is released under the MIT License.