planner: add FastIntSet for functional dependency maintaince (#33021)

ref #29766

planner/funcdep/fast_int_set.go

@@ -0,0 +1,390 @@
+// Copyright 2022 PingCAP, Inc.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package funcdep
+
+import (
+	"bytes"
+	"fmt"
+	"math/bits"
+
+	"golang.org/x/tools/container/intsets"
+)
+
+const smallCutOff = 64
+
+// FastIntSet is wrapper of sparse with an optimization that number [0 ~ 64) can be cached for quick access.
+// From the benchmark in fd_graph_test.go, we choose to use sparse to accelerate int set. And when the set
+// size is quite small we can just skip the block allocation in the sparse chain list.
+type FastIntSet struct {
+	// an uint64 used like quick-small bitmap of 0~63.
+	small uint64
+	// when some is bigger than 64, then all that previous inserted will be dumped into sparse.
+	large *intsets.Sparse
+}
+
+// NewFastIntSet is used to make the instance of FastIntSet with initial values.
+func NewFastIntSet(values ...int) FastIntSet {
+	var res FastIntSet
+	for _, v := range values {
+		res.Insert(v)
+	}
+	return res
+}
+
+// Len return the size of the int set.
+func (s FastIntSet) Len() int {
+	if s.large == nil {
+		return bits.OnesCount64(s.small)
+	}
+	return s.large.Len()
+}
+
+// Only1Zero is a usage function for convenience judgement.
+func (s FastIntSet) Only1Zero() bool {
+	return s.Len() == 1 && s.Has(0)
+}
+
+// Insert is used to insert a value into int-set.
+func (s *FastIntSet) Insert(i int) {
+	isSmall := i >= 0 && i < smallCutOff
+	if isSmall {
+		s.small |= 1 << uint64(i)
+	}
+	if !isSmall && s.large == nil {
+		// first encounter a larger/smaller number, dump all that in `small` into `large`.
+		s.large = s.toLarge()
+	}
+	if s.large != nil {
+		s.large.Insert(i)
+	}
+}
+
+func (s FastIntSet) toLarge() *intsets.Sparse {
+	if s.large != nil {
+		return s.large
+	}
+	large := new(intsets.Sparse)
+	for i, ok := s.Next(0); ok; i, ok = s.Next(i + 1) {
+		large.Insert(i)
+	}
+	return large
+}
+
+// Next returns the next existing number in the Set. If there's no larger one than the given start val, return (MaxInt, false).
+func (s FastIntSet) Next(startVal int) (int, bool) {
+	if startVal < smallCutOff {
+		if startVal < 0 {
+			startVal = 0
+		}
+		// x=0, gap=64, which means there is no `1` after right shift.
+		if gap := bits.TrailingZeros64(s.small >> uint64(startVal)); gap < 64 {
+			return gap + startVal, true
+		}
+	}
+	if s.large != nil {
+		res := s.large.LowerBound(startVal)
+		return res, res != intsets.MaxInt
+	}
+	return intsets.MaxInt, false
+}
+
+// Remove is used to remove a value from the set. Nothing done if the value is not in the set.
+func (s *FastIntSet) Remove(i int) {
+	if i >= 0 && i < smallCutOff {
+		s.small &^= 1 << uint64(i)
+	}
+	if s.large != nil {
+		s.large.Remove(i)
+	}
+}
+
+// Clear is used to clear a fastIntSet and reuse it as an empty one.
+func (s *FastIntSet) Clear() {
+	s.small = 0
+	if s.large != nil {
+		s.large.Clear()
+	}
+}
+
+// Has is used ot judge whether a value is in the set.
+func (s FastIntSet) Has(i int) bool {
+	if i >= 0 && i < smallCutOff {
+		return (s.small & (1 << uint64(i))) != 0
+	}
+	if s.large != nil {
+		return s.large.Has(i)
+	}
+	return false
+}
+
+// IsEmpty is used to judge whether the int-set is empty.
+func (s FastIntSet) IsEmpty() bool {
+	return s.small == 0 && (s.large == nil || s.large.IsEmpty())
+}
+
+// SortedArray is used to return the in array of the set.
+func (s FastIntSet) SortedArray() []int {
+	if s.IsEmpty() {
+		return nil
+	}
+	if s.large != nil {
+		return s.large.AppendTo([]int(nil))
+	}
+	res := make([]int, 0, s.Len())
+	s.ForEach(func(i int) {
+		res = append(res, i)
+	})
+	return res
+}
+
+// ForEach call a function for each value in the int-set. (Ascend)
+func (s FastIntSet) ForEach(f func(i int)) {
+	if s.large != nil {
+		for x := s.large.Min(); x != intsets.MaxInt; x = s.large.LowerBound(x + 1) {
+			f(x)
+		}
+		return
+	}
+	for v := s.small; v != 0; {
+		// from the left to right.
+		i := bits.TrailingZeros64(v)
+		f(i)
+		v &^= 1 << uint(i)
+	}
+}
+
+// Copy returns a copy of s.
+func (s FastIntSet) Copy() FastIntSet {
+	c := FastIntSet{}
+	c.small = s.small
+	if s.large != nil {
+		c.large = new(intsets.Sparse)
+		c.large.Copy(s.large)
+	}
+	return c
+}
+
+// CopyFrom clear the receiver to be a copy of the param.
+func (s *FastIntSet) CopyFrom(target FastIntSet) {
+	s.small = target.small
+	if target.large != nil {
+		if s.large == nil {
+			s.large = new(intsets.Sparse)
+		}
+		s.large.Copy(target.large)
+	} else {
+		if s.large != nil {
+			s.large.Clear()
+		}
+	}
+}
+
+// Equals returns whether two int-set are identical.
+func (s FastIntSet) Equals(rhs FastIntSet) bool {
+	if s.large == nil && rhs.large == nil {
+		return s.small == rhs.small
+	}
+	if s.large != nil && rhs.large != nil {
+		return s.large.Equals(rhs.large)
+	}
+	// how come to this? eg: a set operates like: {insert:1, insert:65, remove:65}, resulting a large int-set with only small numbers.
+	// so we need calculate the exact numbers.
+	var excess bool
+	s1 := s.small
+	s2 := rhs.small
+	if s.large != nil {
+		s1, excess = s.largeToSmall()
+	} else {
+		s2, excess = rhs.largeToSmall()
+	}
+	return !excess && s1 == s2
+}
+
+func (s FastIntSet) largeToSmall() (small uint64, otherValues bool) {
+	if s.large == nil {
+		panic("set contains no large")
+	}
+	return s.small, s.large.Min() < 0 || s.large.Max() >= smallCutOff
+}
+
+// *************************************************************************
+// *                            Logic Operators                            *
+// *************************************************************************
+
+// Difference is used to return the s without elements in rhs.
+func (s FastIntSet) Difference(rhs FastIntSet) FastIntSet {
+	r := s.Copy()
+	r.DifferenceWith(rhs)
+	return r
+}
+
+// DifferenceWith removes any elements in rhs from source.
+func (s *FastIntSet) DifferenceWith(rhs FastIntSet) {
+	s.small &^= rhs.small
+	if s.large == nil {
+		return
+	}
+	s.large.DifferenceWith(rhs.toLarge())
+}
+
+// Union is used to return a union of s and rhs as new set.
+func (s FastIntSet) Union(rhs FastIntSet) FastIntSet {
+	cps := s.Copy()
+	cps.UnionWith(rhs)
+	return cps
+}
+
+// UnionWith is used to copy all the elements of rhs to source.
+func (s *FastIntSet) UnionWith(rhs FastIntSet) {
+	s.small |= rhs.small
+	if s.large == nil && rhs.large == nil {
+		return
+	}
+	if s.large == nil {
+		s.large = s.toLarge()
+	}
+	if rhs.large == nil {
+		for i, ok := rhs.Next(0); ok; i, ok = rhs.Next(i + 1) {
+			s.large.Insert(i)
+		}
+	} else {
+		s.large.UnionWith(rhs.large)
+	}
+}
+
+// Intersection is used to return the intersection of s and rhs.
+func (s FastIntSet) Intersection(rhs FastIntSet) FastIntSet {
+	r := s.Copy()
+	r.IntersectionWith(rhs)
+	return r
+}
+
+// IntersectionWith removes any elements not in rhs from source.
+func (s *FastIntSet) IntersectionWith(rhs FastIntSet) {
+	s.small &= rhs.small
+	if rhs.large == nil {
+		s.large = nil
+	}
+	if s.large == nil {
+		return
+	}
+	s.large.IntersectionWith(rhs.toLarge())
+}
+
+// Intersects is used to judge whether two set has something in common.
+func (s FastIntSet) Intersects(rhs FastIntSet) bool {
+	if (s.small & rhs.small) != 0 {
+		return true
+	}
+	if s.large == nil || rhs.large == nil {
+		return false
+	}
+	return s.large.Intersects(rhs.toLarge())
+}
+
+// SubsetOf is used to judge whether rhs contains source set.
+func (s FastIntSet) SubsetOf(rhs FastIntSet) bool {
+	if s.large == nil {
+		return (s.small & rhs.small) == s.small
+	}
+	if s.large != nil && rhs.large != nil {
+		return s.large.SubsetOf(rhs.large)
+	}
+	// s is large and rhs is small.
+	if _, excess := s.largeToSmall(); excess {
+		// couldn't map s to small.
+		return false
+	}
+	// how come to this? eg: a set operates like: {insert:1, insert:65, remove:65}, resulting a large
+	// int-set with only small numbers.
+	return (s.small & rhs.small) == s.small
+}
+
+// Shift generates a new set which contains elements i+delta for elements i in
+// the original set.
+func (s *FastIntSet) Shift(delta int) FastIntSet {
+	if s.large == nil {
+		// Fast path.
+		if delta > 0 {
+			if bits.LeadingZeros64(s.small)-(64-smallCutOff) >= delta {
+				return FastIntSet{small: s.small << uint32(delta)}
+			}
+		} else {
+			if bits.TrailingZeros64(s.small) >= -delta {
+				return FastIntSet{small: s.small >> uint32(-delta)}
+			}
+		}
+	}
+	// Do the slow thing.
+	var result FastIntSet
+	s.ForEach(func(i int) {
+		result.Insert(i + delta)
+	})
+	return result
+}
+
+// AddRange adds the interval [from, to] to the Set.
+func (s *FastIntSet) AddRange(from, to int) {
+	if to < from {
+		panic("invalid range when adding range to FastIntSet")
+	}
+
+	withinSmallBounds := from >= 0 && to < smallCutOff
+	if withinSmallBounds && s.large == nil {
+		nValues := to - from + 1
+		s.small |= (1<<uint64(nValues) - 1) << uint64(from)
+	} else {
+		for i := from; i <= to; i++ {
+			s.Insert(i)
+		}
+	}
+}
+
+func (s FastIntSet) String() string {
+	var buf bytes.Buffer
+	buf.WriteByte('(')
+	appendRange := func(start, end int) {
+		if buf.Len() > 1 {
+			buf.WriteByte(',')
+		}
+		if start == end {
+			fmt.Fprintf(&buf, "%d", start)
+		} else if start+1 == end {
+			fmt.Fprintf(&buf, "%d,%d", start, end)
+		} else {
+			fmt.Fprintf(&buf, "%d-%d", start, end)
+		}
+	}
+	rangeStart, rangeEnd := -1, -1
+	s.ForEach(func(i int) {
+		if i < 0 {
+			appendRange(i, i)
+			return
+		}
+		if rangeStart != -1 && rangeEnd == i-1 {
+			rangeEnd = i
+		} else {
+			if rangeStart != -1 {
+				appendRange(rangeStart, rangeEnd)
+			}
+			rangeStart, rangeEnd = i, i
+		}
+	})
+	if rangeStart != -1 {
+		appendRange(rangeStart, rangeEnd)
+	}
+	buf.WriteByte(')')
+	return buf.String()
+}