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iterate.go
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iterate.go
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package graph
import (
"encoding/json"
"fmt"
"github.com/cayleygraph/cayley/clog"
"github.com/cayleygraph/cayley/quad"
"golang.org/x/net/context"
)
// IterateChain is a chain-enabled helper to setup iterator execution.
type IterateChain struct {
ctx context.Context
it Iterator
qs QuadStore
paths bool
optimize bool
limit int
n int
}
// Iterate is a set of helpers for iteration. Context may be used to cancel execution.
// Iterator will be optimized and closed after execution.
//
// By default, iteration has no limit and includes sub-paths.
func Iterate(ctx context.Context, it Iterator) *IterateChain {
if ctx == nil {
ctx = context.Background()
}
return &IterateChain{
ctx: ctx, it: it,
limit: -1, paths: true,
optimize: true,
}
}
func (c *IterateChain) next() bool {
select {
case <-c.ctx.Done():
return false
default:
}
ok := (c.limit < 0 || c.n < c.limit) && c.it.Next()
if ok {
c.n++
}
return ok
}
func (c *IterateChain) nextPath() bool {
select {
case <-c.ctx.Done():
return false
default:
}
ok := c.paths && (c.limit < 0 || c.n < c.limit) && c.it.NextPath()
if ok {
c.n++
}
return ok
}
func (c *IterateChain) start() {
if c.optimize {
c.it, _ = c.it.Optimize()
if c.qs != nil {
c.it, _ = c.qs.OptimizeIterator(c.it)
}
}
if !clog.V(2) {
return
}
if b, err := json.MarshalIndent(c.it.Describe(), "", " "); err != nil {
clog.Infof("failed to format description: %v", err)
} else {
clog.Infof("%s", b)
}
}
func (c *IterateChain) end() {
c.it.Close()
if !clog.V(2) {
return
}
if b, err := json.MarshalIndent(DumpStats(c.it), "", " "); err != nil {
clog.Infof("failed to format stats: %v", err)
} else {
clog.Infof("%s", b)
}
}
// Limit limits a total number of results returned.
func (c *IterateChain) Limit(n int) *IterateChain {
c.limit = n
return c
}
// Paths switches iteration over sub-paths (with it.NextPath).
// Defaults to true.
func (c *IterateChain) Paths(enable bool) *IterateChain {
c.paths = enable
return c
}
// On sets a default quad store for iteration. If qs was set, it may be omitted in other functions.
func (c *IterateChain) On(qs QuadStore) *IterateChain {
c.qs = qs
return c
}
// UnOptimized disables iterator optimization.
func (c *IterateChain) UnOptimized() *IterateChain {
c.optimize = false
return c
}
// Each will run a provided callback for each result of the iterator.
func (c *IterateChain) Each(fnc func(Value)) error {
c.start()
defer c.end()
done := c.ctx.Done()
for c.next() {
select {
case <-done:
return c.ctx.Err()
default:
}
fnc(c.it.Result())
for c.nextPath() {
select {
case <-done:
return c.ctx.Err()
default:
}
fnc(c.it.Result())
}
}
return c.it.Err()
}
// All will return all results of an iterator.
func (c *IterateChain) All() ([]Value, error) {
c.start()
defer c.end()
done := c.ctx.Done()
var out []Value
iteration:
for c.next() {
select {
case <-done:
break iteration
default:
}
out = append(out, c.it.Result())
for c.nextPath() {
select {
case <-done:
break iteration
default:
}
out = append(out, c.it.Result())
}
}
return out, c.it.Err()
}
// Send will send each result of the iterator to the provided channel.
//
// Channel will NOT be closed when function returns.
func (c *IterateChain) Send(out chan<- Value) error {
c.start()
defer c.end()
done := c.ctx.Done()
for c.next() {
select {
case <-done:
return c.ctx.Err()
case out <- c.it.Result():
}
for c.nextPath() {
select {
case <-done:
return c.ctx.Err()
case out <- c.it.Result():
}
}
}
return c.it.Err()
}
// TagEach will run a provided tag map callback for each result of the iterator.
func (c *IterateChain) TagEach(fnc func(map[string]Value)) error {
c.start()
defer c.end()
done := c.ctx.Done()
for c.next() {
select {
case <-done:
return c.ctx.Err()
default:
}
tags := make(map[string]Value)
c.it.TagResults(tags)
fnc(tags)
for c.nextPath() {
select {
case <-done:
return c.ctx.Err()
default:
}
tags := make(map[string]Value)
c.it.TagResults(tags)
fnc(tags)
}
}
return c.it.Err()
}
var errNoQuadStore = fmt.Errorf("no quad store in Iterate")
// EachValue is an analog of Each, but it will additionally call NameOf
// for each graph.Value before passing it to a callback.
func (c *IterateChain) EachValue(qs QuadStore, fnc func(quad.Value)) error {
if qs != nil {
c.qs = qs
}
if c.qs == nil {
return errNoQuadStore
}
// TODO(dennwc): batch NameOf?
return c.Each(func(v Value) {
fnc(c.qs.NameOf(v))
})
}
// EachValuePair is an analog of Each, but it will additionally call NameOf
// for each graph.Value before passing it to a callback. Original value will be passed as well.
func (c *IterateChain) EachValuePair(qs QuadStore, fnc func(Value, quad.Value)) error {
if qs != nil {
c.qs = qs
}
if c.qs == nil {
return errNoQuadStore
}
// TODO(dennwc): batch NameOf?
return c.Each(func(v Value) {
fnc(v, c.qs.NameOf(v))
})
}
// AllValues is an analog of All, but it will additionally call NameOf
// for each graph.Value before returning the results slice.
func (c *IterateChain) AllValues(qs QuadStore) ([]quad.Value, error) {
var out []quad.Value
err := c.EachValue(qs, func(v quad.Value) {
out = append(out, v)
})
return out, err
}
// SendValues is an analog of Send, but it will additionally call NameOf
// for each graph.Value before sending it to a channel.
func (c *IterateChain) SendValues(qs QuadStore, out chan<- quad.Value) error {
if qs != nil {
c.qs = qs
}
if c.qs == nil {
return errNoQuadStore
}
c.start()
defer c.end()
done := c.ctx.Done()
for c.next() {
select {
case <-done:
return c.ctx.Err()
case out <- c.qs.NameOf(c.it.Result()):
}
for c.nextPath() {
select {
case <-done:
return c.ctx.Err()
case out <- c.qs.NameOf(c.it.Result()):
}
}
}
return c.it.Err()
}
// TagValues is an analog of TagEach, but it will additionally call NameOf
// for each graph.Value before passing the map to a callback.
func (c *IterateChain) TagValues(qs QuadStore, fnc func(map[string]quad.Value)) error {
if qs != nil {
c.qs = qs
}
if c.qs == nil {
return errNoQuadStore
}
return c.TagEach(func(m map[string]Value) {
vm := make(map[string]quad.Value, len(m))
for k, v := range m {
vm[k] = c.qs.NameOf(v) // TODO(dennwc): batch NameOf?
}
fnc(vm)
})
}