github.com/weaviate/weaviate@v1.24.6/adapters/repos/db/roaringset/binary_search_tree_cursor.go (about)

     1  //                           _       _
     2  // __      _____  __ ___   ___  __ _| |_ ___
     3  // \ \ /\ / / _ \/ _` \ \ / / |/ _` | __/ _ \
     4  //  \ V  V /  __/ (_| |\ V /| | (_| | ||  __/
     5  //   \_/\_/ \___|\__,_| \_/ |_|\__,_|\__\___|
     6  //
     7  //  Copyright © 2016 - 2024 Weaviate B.V. All rights reserved.
     8  //
     9  //  CONTACT: hello@weaviate.io
    10  //
    11  
    12  package roaringset
    13  
    14  import (
    15  	"bytes"
    16  
    17  	"github.com/weaviate/weaviate/entities/lsmkv"
    18  )
    19  
    20  type BinarySearchTreeCursor struct {
    21  	nodes       []*BinarySearchNode
    22  	nextNodePos int
    23  }
    24  
    25  func NewBinarySearchTreeCursor(bst *BinarySearchTree) *BinarySearchTreeCursor {
    26  	return &BinarySearchTreeCursor{nodes: bst.FlattenInOrder()}
    27  }
    28  
    29  func (c *BinarySearchTreeCursor) First() ([]byte, BitmapLayer, error) {
    30  	c.nextNodePos = 0
    31  	return c.Next()
    32  }
    33  
    34  func (c *BinarySearchTreeCursor) Next() ([]byte, BitmapLayer, error) {
    35  	if c.nextNodePos >= len(c.nodes) {
    36  		return nil, BitmapLayer{}, nil
    37  	}
    38  
    39  	pos := c.nextNodePos
    40  	c.nextNodePos++
    41  	return c.nodes[pos].Key, c.nodes[pos].Value, nil
    42  }
    43  
    44  func (c *BinarySearchTreeCursor) Seek(key []byte) ([]byte, BitmapLayer, error) {
    45  	pos := c.posKeyGreaterThanEqual(key)
    46  	if pos == -1 {
    47  		return nil, BitmapLayer{}, lsmkv.NotFound
    48  	}
    49  	c.nextNodePos = pos
    50  	return c.Next()
    51  }
    52  
    53  func (c *BinarySearchTreeCursor) posKeyGreaterThanEqual(key []byte) int {
    54  	// seek from the end, return position of first (from the beginning) node with key >= given key
    55  	// if key > node_key return previous pos
    56  	// if key == node_key return current pos
    57  	// if key < node_key continue or return current pos if all nodes checked
    58  	pos := -1
    59  	for i := len(c.nodes) - 1; i >= 0; i-- {
    60  		if cmp := bytes.Compare(key, c.nodes[i].Key); cmp > 0 {
    61  			break
    62  		} else if cmp == 0 {
    63  			pos = i
    64  			break
    65  		}
    66  		pos = i
    67  	}
    68  	return pos
    69  }