github.com/dolthub/dolt/go@v0.40.5-0.20240520175717-68db7794bea6/store/diff/patch.go (about) 1 // Copyright 2019 Dolthub, Inc. 2 // 3 // Licensed under the Apache License, Version 2.0 (the "License"); 4 // you may not use this file except in compliance with the License. 5 // You may obtain a copy of the License at 6 // 7 // http://www.apache.org/licenses/LICENSE-2.0 8 // 9 // Unless required by applicable law or agreed to in writing, software 10 // distributed under the License is distributed on an "AS IS" BASIS, 11 // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 12 // See the License for the specific language governing permissions and 13 // limitations under the License. 14 // 15 // This file incorporates work covered by the following copyright and 16 // permission notice: 17 // 18 // Copyright 2016 Attic Labs, Inc. All rights reserved. 19 // Licensed under the Apache License, version 2.0: 20 // http://www.apache.org/licenses/LICENSE-2.0 21 22 package diff 23 24 import ( 25 "bytes" 26 "context" 27 28 "github.com/dolthub/dolt/go/store/types" 29 ) 30 31 // Patch is a list of difference objects that can be applied to a graph 32 // using ApplyPatch(). Patch implements a sort order that is useful for 33 // applying the patch in an efficient way. 34 type Patch []Difference 35 36 type PatchSort struct { 37 patch Patch 38 } 39 40 func (ps PatchSort) Swap(i, j int) { 41 ps.patch[i], ps.patch[j] = ps.patch[j], ps.patch[i] 42 } 43 44 func (ps PatchSort) Len() int { 45 return len(ps.patch) 46 } 47 48 var vals = map[types.DiffChangeType]int{types.DiffChangeRemoved: 0, types.DiffChangeModified: 1, types.DiffChangeAdded: 2} 49 50 func (ps PatchSort) Less(ctx context.Context, nbf *types.NomsBinFormat, i, j int) (bool, error) { 51 if ps.patch[i].Path.Equals(ps.patch[j].Path) { 52 return vals[ps.patch[i].ChangeType] < vals[ps.patch[j].ChangeType], nil 53 } 54 return pathIsLess(ctx, nbf, ps.patch[i].Path, ps.patch[j].Path) 55 } 56 57 // Utility methods on path 58 // TODO: Should these be on types.Path & types.PathPart? 59 func pathIsLess(ctx context.Context, nbf *types.NomsBinFormat, p1, p2 types.Path) (bool, error) { 60 for i, pp1 := range p1 { 61 if len(p2) == i { 62 return false, nil // p1 > p2 63 } 64 65 idx, err := pathPartCompare(ctx, nbf, pp1, p2[i]) 66 67 if err != nil { 68 return false, err 69 } 70 71 switch idx { 72 case -1: 73 return true, nil // p1 < p2 74 case 1: 75 return false, nil // p1 > p2 76 } 77 } 78 79 return len(p2) > len(p1), nil // if true p1 < p2, else p1 == p2 80 } 81 82 func fieldPathCompare(pp types.FieldPath, o types.PathPart) int { 83 switch opp := o.(type) { 84 case types.FieldPath: 85 if pp.Name == opp.Name { 86 return 0 87 } 88 if pp.Name < opp.Name { 89 return -1 90 } 91 return 1 92 case types.IndexPath: 93 return -1 94 case types.HashIndexPath: 95 return -1 96 } 97 panic("unreachable") 98 } 99 100 func indexPathCompare(ctx context.Context, nbf *types.NomsBinFormat, pp types.IndexPath, o types.PathPart) (int, error) { 101 switch opp := o.(type) { 102 case types.FieldPath: 103 return 1, nil 104 case types.IndexPath: 105 if pp.Index.Equals(opp.Index) { 106 if pp.IntoKey == opp.IntoKey { 107 return 0, nil 108 } 109 if pp.IntoKey { 110 return -1, nil 111 } 112 return 1, nil 113 } 114 if isLess, err := pp.Index.Less(ctx, nbf, opp.Index); err != nil { 115 return 0, err 116 } else if isLess { 117 return -1, nil 118 } 119 return 1, nil 120 case types.HashIndexPath: 121 return -1, nil 122 } 123 panic("unreachable") 124 } 125 126 func hashIndexPathCompare(pp types.HashIndexPath, o types.PathPart) int { 127 switch opp := o.(type) { 128 case types.FieldPath: 129 return 1 130 case types.IndexPath: 131 return 1 132 case types.HashIndexPath: 133 switch bytes.Compare(pp.Hash[:], opp.Hash[:]) { 134 case -1: 135 return -1 136 case 0: 137 if pp.IntoKey == opp.IntoKey { 138 return 0 139 } 140 if pp.IntoKey { 141 return -1 142 } 143 return 1 144 case 1: 145 return 1 146 } 147 } 148 panic("unreachable") 149 } 150 151 func pathPartCompare(ctx context.Context, nbf *types.NomsBinFormat, pp, pp2 types.PathPart) (int, error) { 152 switch pp1 := pp.(type) { 153 case types.FieldPath: 154 return fieldPathCompare(pp1, pp2), nil 155 case types.IndexPath: 156 return indexPathCompare(ctx, nbf, pp1, pp2) 157 case types.HashIndexPath: 158 return hashIndexPathCompare(pp1, pp2), nil 159 } 160 panic("unreachable") 161 }