MM-42570: Update dependencies (#19901)

https://mattermost.atlassian.net/browse/MM-42570 ```release-note NONE ```
2022-04-06 04:14:42 +05:30
--- a/vendor/github.com/blevesearch/bleve/v2/SECURITY.md
+++ b/vendor/github.com/blevesearch/bleve/v2/SECURITY.md
@@ -0,0 +1,14 @@
+# Security Policy
+
+## Supported Versions
+
+We support the latest release (for example, bleve v2.3.x).
+
+## Reporting a Vulnerability
+
+All security issues for this project should be reported by email to fts-team@couchbase.com. This mail will be delivered to the owners of this project.
+
+- To ensure your report is NOT marked as spam, please include the word "security/vulnerability" along with the project name (blevesearch/bleve) in the subject of the email.
+- Please be as descriptive as possible while explaining the issue, and a testcase highlighting the issue is always welcome.
+
+Your email will be acknowledged at the soonest possible.
--- a/vendor/github.com/blevesearch/bleve/v2/go.mod
+++ b/vendor/github.com/blevesearch/bleve/v2/go.mod
@@ -6,9 +6,13 @@ require (
 	github.com/RoaringBitmap/roaring v0.9.4
 	github.com/bits-and-blooms/bitset v1.2.0
 	github.com/blevesearch/bleve_index_api v1.0.1
+	github.com/blevesearch/go-metrics v0.0.0-20190826022208-cac0b30c2563
 	github.com/blevesearch/go-porterstemmer v1.0.3
+	github.com/blevesearch/goleveldb v1.0.1
+	github.com/blevesearch/gtreap v0.1.1
 	github.com/blevesearch/scorch_segment_api/v2 v2.1.0
 	github.com/blevesearch/segment v0.9.0
+	github.com/blevesearch/snowball v0.6.1
 	github.com/blevesearch/snowballstem v0.9.0
 	github.com/blevesearch/upsidedown_store_api v1.0.1
 	github.com/blevesearch/vellum v1.0.7
@@ -19,11 +23,7 @@ require (
 	github.com/blevesearch/zapx/v15 v15.3.3
 	github.com/couchbase/moss v0.2.0
 	github.com/golang/protobuf v1.3.2
-	github.com/kljensen/snowball v0.6.0
-	github.com/rcrowley/go-metrics v0.0.0-20190826022208-cac0b30c2563
 	github.com/spf13/cobra v0.0.5
-	github.com/steveyen/gtreap v0.1.0
-	github.com/syndtr/goleveldb v1.0.0
 	go.etcd.io/bbolt v1.3.5
 	golang.org/x/text v0.3.7
 )
--- a/vendor/github.com/blevesearch/bleve/v2/go.sum
+++ b/vendor/github.com/blevesearch/bleve/v2/go.sum
@@ -6,8 +6,14 @@ github.com/bits-and-blooms/bitset v1.2.0 h1:Kn4yilvwNtMACtf1eYDlG8H77R07mZSPbMjL
 github.com/bits-and-blooms/bitset v1.2.0/go.mod h1:gIdJ4wp64HaoK2YrL1Q5/N7Y16edYb8uY+O0FJTyyDA=
 github.com/blevesearch/bleve_index_api v1.0.1 h1:nx9++0hnyiGOHJwQQYfsUGzpRdEVE5LsylmmngQvaFk=
 github.com/blevesearch/bleve_index_api v1.0.1/go.mod h1:fiwKS0xLEm+gBRgv5mumf0dhgFr2mDgZah1pqv1c1M4=
+github.com/blevesearch/go-metrics v0.0.0-20190826022208-cac0b30c2563 h1:mQtHArdP4SdgdR2mY8i+W3u9ekCDWDxcM/3nwehEdiw=
+github.com/blevesearch/go-metrics v0.0.0-20190826022208-cac0b30c2563/go.mod h1:9eJDeqxJ3E7WnLebQUlPD7ZjSce7AnDb9vjGmMCbD0A=
 github.com/blevesearch/go-porterstemmer v1.0.3 h1:GtmsqID0aZdCSNiY8SkuPJ12pD4jI+DdXTAn4YRcHCo=
 github.com/blevesearch/go-porterstemmer v1.0.3/go.mod h1:angGc5Ht+k2xhJdZi511LtmxuEf0OVpvUUNrwmM1P7M=
+github.com/blevesearch/goleveldb v1.0.1 h1:iAtV2Cu5s0GD1lwUiekkFHe2gTMCCNVj2foPclDLIFI=
+github.com/blevesearch/goleveldb v1.0.1/go.mod h1:WrU8ltZbIp0wAoig/MHbrPCXSOLpe79nz5lv5nqfYrQ=
+github.com/blevesearch/gtreap v0.1.1 h1:2JWigFrzDMR+42WGIN/V2p0cUvn4UP3C4Q5nmaZGW8Y=
+github.com/blevesearch/gtreap v0.1.1/go.mod h1:QaQyDRAT51sotthUWAH4Sj08awFSSWzgYICSZ3w0tYk=
 github.com/blevesearch/mmap-go v1.0.2/go.mod h1:ol2qBqYaOUsGdm7aRMRrYGgPvnwLe6Y+7LMvAB5IbSA=
 github.com/blevesearch/mmap-go v1.0.3 h1:7QkALgFNooSq3a46AE+pWeKASAZc9SiNFJhDGF1NDx4=
 github.com/blevesearch/mmap-go v1.0.3/go.mod h1:pYvKl/grLQrBxuaRYgoTssa4rVujYYeenDp++2E+yvs=
@@ -15,6 +21,8 @@ github.com/blevesearch/scorch_segment_api/v2 v2.1.0 h1:NFwteOpZEvJk5Vg0H6gD0hxup
 github.com/blevesearch/scorch_segment_api/v2 v2.1.0/go.mod h1:uch7xyyO/Alxkuxa+CGs79vw0QY8BENSBjg6Mw5L5DE=
 github.com/blevesearch/segment v0.9.0 h1:5lG7yBCx98or7gK2cHMKPukPZ/31Kag7nONpoBt22Ac=
 github.com/blevesearch/segment v0.9.0/go.mod h1:9PfHYUdQCgHktBgvtUOF4x+pc4/l8rdH0u5spnW85UQ=
+github.com/blevesearch/snowball v0.6.1 h1:cDYjn/NCH+wwt2UdehaLpr2e4BwLIjN4V/TdLsL+B5A=
+github.com/blevesearch/snowball v0.6.1/go.mod h1:ZF0IBg5vgpeoUhnMza2v0A/z8m1cWPlwhke08LpNusg=
 github.com/blevesearch/snowballstem v0.9.0 h1:lMQ189YspGP6sXvZQ4WZ+MLawfV8wOmPoD/iWeNXm8s=
 github.com/blevesearch/snowballstem v0.9.0/go.mod h1:PivSj3JMc8WuaFkTSRDW2SlrulNWPl4ABg1tC/hlgLs=
 github.com/blevesearch/upsidedown_store_api v1.0.1 h1:1SYRwyoFLwG3sj0ed89RLtM15amfX2pXlYbFOnF8zNU=
@@ -55,8 +63,6 @@ github.com/hpcloud/tail v1.0.0 h1:nfCOvKYfkgYP8hkirhJocXT2+zOD8yUNjXaWfTlyFKI=
 github.com/hpcloud/tail v1.0.0/go.mod h1:ab1qPbhIpdTxEkNHXyeSf5vhxWSCs/tWer42PpOxQnU=
 github.com/inconshreveable/mousetrap v1.0.0 h1:Z8tu5sraLXCXIcARxBp/8cbvlwVa7Z1NHg9XEKhtSvM=
 github.com/inconshreveable/mousetrap v1.0.0/go.mod h1:PxqpIevigyE2G7u3NXJIT2ANytuPF1OarO4DADm73n8=
-github.com/kljensen/snowball v0.6.0 h1:6DZLCcZeL0cLfodx+Md4/OLC6b/bfurWUOUGs1ydfOU=
-github.com/kljensen/snowball v0.6.0/go.mod h1:27N7E8fVU5H68RlUmnWwZCfxgt4POBJfENGMvNRhldw=
 github.com/magiconair/properties v1.8.0/go.mod h1:PppfXfuXeibc/6YijjN8zIbojt8czPbwD3XqdrwzmxQ=
 github.com/mitchellh/go-homedir v1.1.0/go.mod h1:SfyaCUpYCn1Vlf4IUYiD9fPX4A5wJrkLzIz1N1q0pr0=
 github.com/mitchellh/mapstructure v1.1.2/go.mod h1:FVVH3fgwuzCH5S8UJGiWEs2h04kUh9fWfEaFds41c1Y=
@@ -70,8 +76,6 @@ github.com/onsi/gomega v1.4.3/go.mod h1:ex+gbHU/CVuBBDIJjb2X0qEXbFg53c61hWP/1Cpa
 github.com/pelletier/go-toml v1.2.0/go.mod h1:5z9KED0ma1S8pY6P1sdut58dfprrGBbd/94hg7ilaic=
 github.com/pmezard/go-difflib v1.0.0 h1:4DBwDE0NGyQoBHbLQYPwSUPoCMWR5BEzIk/f1lZbAQM=
 github.com/pmezard/go-difflib v1.0.0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4=
-github.com/rcrowley/go-metrics v0.0.0-20190826022208-cac0b30c2563 h1:dY6ETXrvDG7Sa4vE8ZQG4yqWg6UnOcbqTAahkV813vQ=
-github.com/rcrowley/go-metrics v0.0.0-20190826022208-cac0b30c2563/go.mod h1:bCqnVzQkZxMG4s8nGwiZ5l3QUCyqpo9Y+/ZMZ9VjZe4=
 github.com/russross/blackfriday v1.5.2/go.mod h1:JO/DiYxRf+HjHt06OyowR9PTA263kcR/rfWxYHBV53g=
 github.com/spf13/afero v1.1.2/go.mod h1:j4pytiNVoe2o6bmDsKpLACNPDBIoEAkihy7loJ1B0CQ=
 github.com/spf13/cast v1.3.0/go.mod h1:Qx5cxh0v+4UWYiBimWS+eyWzqEqokIECu5etghLkUJE=
@@ -81,14 +85,10 @@ github.com/spf13/jwalterweatherman v1.0.0/go.mod h1:cQK4TGJAtQXfYWX+Ddv3mKDzgVb6
 github.com/spf13/pflag v1.0.3 h1:zPAT6CGy6wXeQ7NtTnaTerfKOsV6V6F8agHXFiazDkg=
 github.com/spf13/pflag v1.0.3/go.mod h1:DYY7MBk1bdzusC3SYhjObp+wFpr4gzcvqqNjLnInEg4=
 github.com/spf13/viper v1.3.2/go.mod h1:ZiWeW+zYFKm7srdB9IoDzzZXaJaI5eL9QjNiN/DMA2s=
-github.com/steveyen/gtreap v0.1.0 h1:CjhzTa274PyJLJuMZwIzCO1PfC00oRa8d1Kc78bFXJM=
-github.com/steveyen/gtreap v0.1.0/go.mod h1:kl/5J7XbrOmlIbYIXdRHDDE5QxHqpk0cmkT7Z4dM9/Y=
 github.com/stretchr/objx v0.1.0/go.mod h1:HFkY916IF+rwdDfMAkV7OtwuqBVzrE8GR6GFx+wExME=
 github.com/stretchr/testify v1.2.2/go.mod h1:a8OnRcib4nhh0OaRAV+Yts87kKdq0PP7pXfy6kDkUVs=
 github.com/stretchr/testify v1.4.0 h1:2E4SXV/wtOkTonXsotYi4li6zVWxYlZuYNCXe9XRJyk=
 github.com/stretchr/testify v1.4.0/go.mod h1:j7eGeouHqKxXV5pUuKE4zz7dFj8WfuZ+81PSLYec5m4=
-github.com/syndtr/goleveldb v1.0.0 h1:fBdIW9lB4Iz0n9khmH8w27SJ3QEJ7+IgjPEwGSZiFdE=
-github.com/syndtr/goleveldb v1.0.0/go.mod h1:ZVVdQEZoIme9iO1Ch2Jdy24qqXrMMOU6lpPAyBWyWuQ=
 github.com/ugorji/go/codec v0.0.0-20181204163529-d75b2dcb6bc8/go.mod h1:VFNgLljTbGfSG7qAOspJ7OScBnGdDN/yBr0sguwnwf0=
 github.com/xordataexchange/crypt v0.0.3-0.20170626215501-b2862e3d0a77/go.mod h1:aYKd//L2LvnjZzWKhF00oedf4jCCReLcmhLdhm1A27Q=
 go.etcd.io/bbolt v1.3.5 h1:XAzx9gjCb0Rxj7EoqcClPD1d5ZBxZJk0jbuoPHenBt0=
--- a/vendor/github.com/blevesearch/bleve/v2/index/scorch/snapshot_index.go
+++ b/vendor/github.com/blevesearch/bleve/v2/index/scorch/snapshot_index.go
@@ -51,6 +51,15 @@ type asynchSegmentResult struct {

 var reflectStaticSizeIndexSnapshot int

+// DefaultFieldTFRCacheThreshold limits the number of TermFieldReaders(TFR) for
+// a field in an index snapshot. Without this limit, when recycling TFRs, it is
+// possible that a very large number of TFRs may be added to the recycle
+// cache, which could eventually lead to significant memory consumption.
+// This threshold can be overwritten by users at the library level by changing the
+// exported variable, or at the index level by setting the FieldTFRCacheThreshold
+// in the kvConfig.
+var DefaultFieldTFRCacheThreshold uint64 = 10
+
 func init() {
 	var is interface{} = IndexSnapshot{}
 	reflectStaticSizeIndexSnapshot = int(reflect.TypeOf(is).Size())
@@ -558,6 +567,15 @@ func (i *IndexSnapshot) allocTermFieldReaderDicts(field string) (tfr *IndexSnaps
 	}
 }

+func (i *IndexSnapshot) getFieldTFRCacheThreshold() uint64 {
+	if i.parent.config != nil {
+		if _, ok := i.parent.config["FieldTFRCacheThreshold"]; ok {
+			return i.parent.config["FieldTFRCacheThreshold"].(uint64)
+		}
+	}
+	return DefaultFieldTFRCacheThreshold
+}
+
 func (i *IndexSnapshot) recycleTermFieldReader(tfr *IndexSnapshotTermFieldReader) {
 	if !tfr.recycle {
 		// Do not recycle an optimized unadorned term field reader (used for
@@ -579,7 +597,9 @@ func (i *IndexSnapshot) recycleTermFieldReader(tfr *IndexSnapshotTermFieldReader
 	if i.fieldTFRs == nil {
 		i.fieldTFRs = map[string][]*IndexSnapshotTermFieldReader{}
 	}
-	i.fieldTFRs[tfr.field] = append(i.fieldTFRs[tfr.field], tfr)
+	if uint64(len(i.fieldTFRs[tfr.field])) < i.getFieldTFRCacheThreshold() {
+		i.fieldTFRs[tfr.field] = append(i.fieldTFRs[tfr.field], tfr)
+	}
 	i.m2.Unlock()
 }

--- a/vendor/github.com/blevesearch/bleve/v2/index/upsidedown/store/gtreap/iterator.go
+++ b/vendor/github.com/blevesearch/bleve/v2/index/upsidedown/store/gtreap/iterator.go
@@ -21,7 +21,7 @@ import (
 	"bytes"
 	"sync"

-	"github.com/steveyen/gtreap"
+	"github.com/blevesearch/gtreap"
 )

 type Iterator struct {
--- a/vendor/github.com/blevesearch/bleve/v2/index/upsidedown/store/gtreap/reader.go
+++ b/vendor/github.com/blevesearch/bleve/v2/index/upsidedown/store/gtreap/reader.go
@@ -20,7 +20,7 @@ package gtreap
 import (
 	"github.com/blevesearch/upsidedown_store_api"

-	"github.com/steveyen/gtreap"
+	"github.com/blevesearch/gtreap"
 )

 type Reader struct {
--- a/vendor/github.com/blevesearch/bleve/v2/index/upsidedown/store/gtreap/store.go
+++ b/vendor/github.com/blevesearch/bleve/v2/index/upsidedown/store/gtreap/store.go
@@ -26,7 +26,7 @@ import (

 	"github.com/blevesearch/bleve/v2/registry"
 	"github.com/blevesearch/upsidedown_store_api"
-	"github.com/steveyen/gtreap"
+	"github.com/blevesearch/gtreap"
 )

 const Name = "gtreap"
--- a/vendor/github.com/blevesearch/gtreap/.gitignore
+++ b/vendor/github.com/blevesearch/gtreap/.gitignore
@@ -0,0 +1,5 @@
+#*
+*~
+*.test
+tmp
+
--- a/vendor/github.com/blevesearch/gtreap/LICENSE
+++ b/vendor/github.com/blevesearch/gtreap/LICENSE
@@ -0,0 +1,20 @@
+Copyright (C) 2012 Steve Yen
+
+Permission is hereby granted, free of charge, to any person obtaining
+a copy of this software and associated documentation files (the
+"Software"), to deal in the Software without restriction, including
+without limitation the rights to use, copy, modify, merge, publish,
+distribute, sublicense, and/or sell copies of the Software, and to
+permit persons to whom the Software is furnished to do so, subject to
+the following conditions:
+
+The above copyright notice and this permission notice shall be
+included in all copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
+LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
+OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
+WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
--- a/vendor/github.com/blevesearch/gtreap/README.md
+++ b/vendor/github.com/blevesearch/gtreap/README.md
@@ -0,0 +1,90 @@
+gtreap
+------
+
+gtreap is an immutable treap implementation in the Go Language
+
+[![GoDoc](https://godoc.org/github.com/steveyen/gtreap?status.svg)](https://godoc.org/github.com/steveyen/gtreap) [![Build Status](https://drone.io/github.com/steveyen/gtreap/status.png)](https://drone.io/github.com/steveyen/gtreap/latest) [![Coverage Status](https://coveralls.io/repos/steveyen/gtreap/badge.png)](https://coveralls.io/r/steveyen/gtreap)
+
+Overview
+========
+
+gtreap implements an immutable treap data structure in golang.
+
+By treap, this data structure is both a heap and a binary search tree.
+
+By immutable, any updates/deletes to a treap will return a new treap
+which can share internal nodes with the previous treap.  All nodes in
+this implementation are read-only after their creation.  This allows
+concurrent readers to operate safely with concurrent writers as
+modifications only create new data structures and never modify
+existing data structures.  This is a simple approach to achieving MVCC
+or multi-version concurrency control.
+
+By heap, items in the treap follow the heap-priority property, where a
+parent node will have higher priority than its left and right children
+nodes.
+
+By binary search tree, items are store lexigraphically, ordered by a
+user-supplied Compare function.
+
+To get a probabilistic O(lg N) tree height, you should use a random
+priority number during the Upsert() operation.
+
+LICENSE
+=======
+
+MIT
+
+Example
+=======
+
+    import (
+        "math/rand"
+        "github.com/steveyen/gtreap"
+    )
+    
+    func stringCompare(a, b interface{}) int {
+	    return bytes.Compare([]byte(a.(string)), []byte(b.(string)))
+    }
+    
+    t := gtreap.NewTreap(stringCompare)
+    t = t.Upsert("hi", rand.Int())
+    t = t.Upsert("hola", rand.Int())
+    t = t.Upsert("bye", rand.Int())
+    t = t.Upsert("adios", rand.Int())
+    
+    hi = t.Get("hi")
+    bye = t.Get("bye")
+    
+    // Some example Delete()'s...
+    t = t.Delete("bye")
+    nilValueHere = t.Get("bye")
+    t2 = t.Delete("hi")
+    nilValueHere2 = t2.Get("hi")
+    
+    // Since we still hold onto treap t, we can still access "hi".
+    hiStillExistsInTreapT = t.Get("hi")
+    
+    t.VisitAscend("cya", func(i Item) bool {
+        // This visitor callback will be invoked with every item
+        // from "cya" onwards.  So: "hi", "hola".
+        // If we want to stop visiting, return false;
+        // otherwise a true return result means keep visiting items.
+        return true
+    })
+
+Tips
+====
+
+The Upsert() method takes both an Item (an interface{}) and a heap
+priority.  Usually, that priority should be a random int
+(math/rand.Int()) or perhaps even a hash of the item.  However, if you
+want to shuffle more commonly accessed items nearer to the top of the
+treap for faster access, at the potential cost of not approaching a
+probabilistic O(lg N) tree height, then you might tweak the priority.
+
+See also
+========
+
+For a simple, ordered, key-value storage or persistence library built
+on immutable treaps, see: https://github.com/steveyen/gkvlite
--- a/vendor/github.com/blevesearch/gtreap/go.mod
+++ b/vendor/github.com/blevesearch/gtreap/go.mod
@@ -0,0 +1,3 @@
+module github.com/blevesearch/gtreap
+
+go 1.13
--- a/vendor/github.com/blevesearch/gtreap/treap.go
+++ b/vendor/github.com/blevesearch/gtreap/treap.go
@@ -0,0 +1,207 @@
+package gtreap
+
+type Treap struct {
+	compare Compare
+	root    *node
+}
+
+// Compare returns an integer comparing the two items
+// lexicographically. The result will be 0 if a==b, -1 if a < b, and
+// +1 if a > b.
+type Compare func(a, b interface{}) int
+
+// Item can be anything.
+type Item interface{}
+
+type node struct {
+	item     Item
+	priority int
+	left     *node
+	right    *node
+}
+
+func NewTreap(c Compare) *Treap {
+	return &Treap{compare: c, root: nil}
+}
+
+func (t *Treap) Min() Item {
+	n := t.root
+	if n == nil {
+		return nil
+	}
+	for n.left != nil {
+		n = n.left
+	}
+	return n.item
+}
+
+func (t *Treap) Max() Item {
+	n := t.root
+	if n == nil {
+		return nil
+	}
+	for n.right != nil {
+		n = n.right
+	}
+	return n.item
+}
+
+func (t *Treap) Get(target Item) Item {
+	n := t.root
+	for n != nil {
+		c := t.compare(target, n.item)
+		if c < 0 {
+			n = n.left
+		} else if c > 0 {
+			n = n.right
+		} else {
+			return n.item
+		}
+	}
+	return nil
+}
+
+// Note: only the priority of the first insert of an item is used.
+// Priorities from future updates on already existing items are
+// ignored.  To change the priority for an item, you need to do a
+// Delete then an Upsert.
+func (t *Treap) Upsert(item Item, itemPriority int) *Treap {
+	r := t.union(t.root, &node{item: item, priority: itemPriority})
+	return &Treap{compare: t.compare, root: r}
+}
+
+func (t *Treap) union(this *node, that *node) *node {
+	if this == nil {
+		return that
+	}
+	if that == nil {
+		return this
+	}
+	if this.priority > that.priority {
+		left, middle, right := t.split(that, this.item)
+		if middle == nil {
+			return &node{
+				item:     this.item,
+				priority: this.priority,
+				left:     t.union(this.left, left),
+				right:    t.union(this.right, right),
+			}
+		}
+		return &node{
+			item:     middle.item,
+			priority: this.priority,
+			left:     t.union(this.left, left),
+			right:    t.union(this.right, right),
+		}
+	}
+	// We don't use middle because the "that" has precendence.
+	left, _, right := t.split(this, that.item)
+	return &node{
+		item:     that.item,
+		priority: that.priority,
+		left:     t.union(left, that.left),
+		right:    t.union(right, that.right),
+	}
+}
+
+// Splits a treap into two treaps based on a split item "s".
+// The result tuple-3 means (left, X, right), where X is either...
+// nil - meaning the item s was not in the original treap.
+// non-nil - returning the node that had item s.
+// The tuple-3's left result treap has items < s,
+// and the tuple-3's right result treap has items > s.
+func (t *Treap) split(n *node, s Item) (*node, *node, *node) {
+	if n == nil {
+		return nil, nil, nil
+	}
+	c := t.compare(s, n.item)
+	if c == 0 {
+		return n.left, n, n.right
+	}
+	if c < 0 {
+		left, middle, right := t.split(n.left, s)
+		return left, middle, &node{
+			item:     n.item,
+			priority: n.priority,
+			left:     right,
+			right:    n.right,
+		}
+	}
+	left, middle, right := t.split(n.right, s)
+	return &node{
+		item:     n.item,
+		priority: n.priority,
+		left:     n.left,
+		right:    left,
+	}, middle, right
+}
+
+func (t *Treap) Delete(target Item) *Treap {
+	left, _, right := t.split(t.root, target)
+	return &Treap{compare: t.compare, root: t.join(left, right)}
+}
+
+// All the items from this are < items from that.
+func (t *Treap) join(this *node, that *node) *node {
+	if this == nil {
+		return that
+	}
+	if that == nil {
+		return this
+	}
+	if this.priority > that.priority {
+		return &node{
+			item:     this.item,
+			priority: this.priority,
+			left:     this.left,
+			right:    t.join(this.right, that),
+		}
+	}
+	return &node{
+		item:     that.item,
+		priority: that.priority,
+		left:     t.join(this, that.left),
+		right:    that.right,
+	}
+}
+
+// ItemVistor callback should return true to keep going on the visitation.
+type ItemVisitor func(i Item) bool
+
+// Visit items greater-than-or-equal to the pivot, in ascending order.
+func (t *Treap) VisitAscend(pivot Item, visitor ItemVisitor) {
+	t.visitAscend(t.root, pivot, visitor)
+}
+
+func (t *Treap) visitAscend(n *node, pivot Item, visitor ItemVisitor) bool {
+	if n == nil {
+		return true
+	}
+	c := t.compare(pivot, n.item)
+	if c < 0 && !t.visitAscend(n.left, pivot, visitor) {
+		return false
+	}
+	if c <= 0 && !visitor(n.item) {
+		return false
+	}
+	return t.visitAscend(n.right, pivot, visitor)
+}
+
+// Visit items less-than-or-equal to the pivot, in descending order.
+func (t *Treap) VisitDescend(pivot Item, visitor ItemVisitor) {
+	t.visitDescend(t.root, pivot, visitor)
+}
+
+func (t *Treap) visitDescend(n *node, pivot Item, visitor ItemVisitor) bool {
+	if n == nil {
+		return true
+	}
+	c := t.compare(pivot, n.item)
+	if c > 0 && !t.visitDescend(n.right, pivot, visitor) {
+		return false
+	}
+	if c >= 0 && !visitor(n.item) {
+		return false
+	}
+	return t.visitDescend(n.left, pivot, visitor)
+}