github.com/dolthub/dolt/go@v0.40.5-0.20240520175717-68db7794bea6/store/val/keyless_tuple.go (about)

     1  // Copyright 2022 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  package val
    16  
    17  import (
    18  	"bytes"
    19  	"encoding/binary"
    20  
    21  	"github.com/zeebo/xxh3"
    22  
    23  	"github.com/dolthub/dolt/go/store/pool"
    24  )
    25  
    26  const (
    27  	keylessCardSz  = uint64Size
    28  	keylessHashSz  = hash128Size
    29  	keylessTupleSz = keylessHashSz + 2
    30  )
    31  
    32  func HashTupleFromValue(pool pool.BuffPool, value Tuple) (key Tuple) {
    33  	if len(value) < 2 || value.FieldIsNull(0) {
    34  		panic("invalid keyless value")
    35  	}
    36  
    37  	// omit the cardinality field from the hash id
    38  	fields := value[keylessCardSz:]
    39  
    40  	key = pool.Get(uint64(keylessTupleSz))
    41  	h := xxh3.Hash128(fields)
    42  	binary.LittleEndian.PutUint64(key[0:8], h.Lo)
    43  	binary.LittleEndian.PutUint64(key[8:keylessHashSz], h.Hi)
    44  	copy(key[keylessHashSz:], keySuffix[:])
    45  	return
    46  }
    47  
    48  func ReadHashFromTuple(keylessKey Tuple) []byte {
    49  	return keylessKey[keylessHashSz:]
    50  }
    51  
    52  func ReadKeylessCardinality(value Tuple) uint64 {
    53  	return readUint64(value[:keylessCardSz])
    54  }
    55  
    56  func ModifyKeylessCardinality(pool pool.BuffPool, value Tuple, delta int64) (updated Tuple, after uint64) {
    57  	updated = cloneTuple(pool, value)
    58  	buf := updated[:keylessCardSz]
    59  	after = uint64(int64(readUint64(buf)) + delta)
    60  	writeUint64(buf, after)
    61  	return
    62  }
    63  
    64  // field count of 1, little endian encoded
    65  var keySuffix = [...]byte{1, 0}
    66  
    67  var KeylessTupleDesc = TupleDesc{
    68  	Types: []Type{{Enc: Hash128Enc, Nullable: false}},
    69  	cmp:   keylessCompare{},
    70  }
    71  
    72  var KeylessCardType = Type{
    73  	Enc:      Uint64Enc,
    74  	Nullable: false,
    75  }
    76  
    77  type keylessCompare struct{}
    78  
    79  var _ TupleComparator = keylessCompare{}
    80  
    81  // Compare implements TupleComparator
    82  func (k keylessCompare) Compare(left, right Tuple, _ TupleDesc) int {
    83  	return bytes.Compare(left, right)
    84  }
    85  
    86  // CompareValues implements TupleComparator
    87  func (k keylessCompare) CompareValues(_ int, left, right []byte, typ Type) int {
    88  	return compare(typ, left, right)
    89  }
    90  
    91  // Prefix implements TupleComparator
    92  func (k keylessCompare) Prefix(n int) TupleComparator {
    93  	return k
    94  }
    95  
    96  // Suffix implements TupleComparator
    97  func (k keylessCompare) Suffix(n int) TupleComparator {
    98  	return k
    99  }
   100  
   101  func (k keylessCompare) Validated(types []Type) TupleComparator {
   102  	return k
   103  }