go.etcd.io/bbolt v1.5.0: iterate seek and delete key-value pairs with bbolt Cursor

Clean-room public code sample — generation instructions

Write a brand-new, minimal, self-contained code sample in this clean-room directory.
Do not copy, paraphrase, or reference any existing project source. Work only from this spec.

A csx.json manifest scaffold already exists. Do not recreate it from memory. Preserve its case.goal, packages and symbols; fill its empty case.contract with exact assertions and correct its environment, commands and verifierAdapter for the files you generate.

Goal: iterate seek and delete key-value pairs with bbolt Cursor
Kind: HOW

Use EXACTLY these public packages and versions:
  - pkg:golang/go.etcd.io/bbolt@v1.5.0
Demonstrate these symbols/APIs:
  - bbolt.Cursor

Rules:
  - One focused purpose; the smallest project that proves the goal.
  - Include a contract test (test/contract.*) that runs OFFLINE and exits 0 exactly when the goal behavior works.
  - Pin every dependency with a lockfile so resolution is reproducible.
  - No secrets, credentials, or tokens. No real URLs (only example.com or localhost). No absolute paths.
  - No personal names, emails, company names, or project identifiers of any kind.
  - No binaries and no generated output (node_modules, dist, target, venv, .git, .env).
  - Keep it under 200 files and 256KB packed.

{"case":{"caseId":"case:sha256:696acfe623f9298a5f754ce97ace70ab30d4bcefba228fa6d2d08018f37699e1","contract":["Bucket.Cursor creates a Cursor positioned at the beginning of the bucket","Cursor.First and Cursor.Next iterate forward through key-value pairs in lexicographical order","Cursor.Last and Cursor.Prev iterate backward through key-value pairs","Cursor.Seek positions the cursor at the first key greater than or equal to the target prefix","Cursor.Delete removes the current key-value pair under the cursor in a writable transaction"],"goal":"iterate seek and delete key-value pairs with bbolt Cursor","kind":"HOW","packages":["pkg:golang/go.etcd.io/bbolt@v1.5.0"],"schemaVersion":1,"symbols":["bbolt.Cursor"]},"contractCommand":["go","run","./test"],"environment":{"arch":"x64","distro":"ubuntu","ecosystem":"golang","libc":"glibc","libcVersion":"2.39","os":"linux","osVersionBucket":"24","packageManager":"go","schemaVersion":1},"license":"MIT-0","packages":["pkg:golang/go.etcd.io/bbolt@v1.5.0"],"schemaVersion":1,"subject":"pkg:golang/go.etcd.io/bbolt@v1.5.0","symbols":["bbolt.Cursor"],"verifierAdapter":"golang@1"}

module sample

go 1.25.0

require go.etcd.io/bbolt v1.5.0

require golang.org/x/sys v0.45.0 // indirect

github.com/davecgh/go-spew v1.1.1 h1:vj9j/u1bqnvCEfJOwUhtlOARqs3+rkHYY13jYWTU97c=
github.com/davecgh/go-spew v1.1.1/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
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/stretchr/testify v1.11.1 h1:7s2iGBzp5EwR7/aIZr8ao5+dra3wiQyKjjFuvgVKu7U=
github.com/stretchr/testify v1.11.1/go.mod h1:wZwfW3scLgRK+23gO65QZefKpKQRnfz6sD981Nm4B6U=
go.etcd.io/bbolt v1.5.0 h1:S7GAl7Fxv12yohbwFfIbQCGDWbQbtDGPET4P/bD4lxU=
go.etcd.io/bbolt v1.5.0/go.mod h1:mkltfYE5aUHQxUct9N9V+Kp7aSjFqjgrhcXIS70Lrdk=
golang.org/x/sync v0.20.0 h1:e0PTpb7pjO8GAtTs2dQ6jYa5BWYlMuX047Dco/pItO4=
golang.org/x/sync v0.20.0/go.mod h1:9xrNwdLfx4jkKbNva9FpL6vEN7evnE43NNNJQ2LF3+0=
golang.org/x/sys v0.45.0 h1:dO4czNzziLiiXplLQgBCEpCvXQ3dnkn0SdaZSYdQ+FY=
golang.org/x/sys v0.45.0/go.mod h1:4GL1E5IUh+htKOUEOaiffhrAeqysfVGipDYzABqnCmw=
gopkg.in/yaml.v3 v3.0.1 h1:fxVm/GzAzEWqLHuvctI91KS9hhNmmWOoWu0XTYJS7CA=
gopkg.in/yaml.v3 v3.0.1/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=

package sample

import (
	"bytes"
	"errors"
	"fmt"

	bolt "go.etcd.io/bbolt"
)

// OpenDatabase creates or opens a Bolt database at the specified path.
func OpenDatabase(path string) (*bolt.DB, error) {
	return bolt.Open(path, 0600, nil)
}

// PopulateBucket creates a bucket and inserts key-value pairs.
func PopulateBucket(db *bolt.DB, bucketName string, items map[string]string) error {
	return db.Update(func(tx *bolt.Tx) error {
		b, err := tx.CreateBucketIfNotExists([]byte(bucketName))
		if err != nil {
			return fmt.Errorf("create bucket: %w", err)
		}
		for k, v := range items {
			if err := b.Put([]byte(k), []byte(v)); err != nil {
				return fmt.Errorf("put %s: %w", k, err)
			}
		}
		return nil
	})
}

// CollectForward traverses all key-value pairs from start to end using Cursor.First and Cursor.Next.
func CollectForward(db *bolt.DB, bucketName string) ([]string, []string, error) {
	var keys []string
	var vals []string

	err := db.View(func(tx *bolt.Tx) error {
		b := tx.Bucket([]byte(bucketName))
		if b == nil {
			return errors.New("bucket not found")
		}
		c := b.Cursor()
		for k, v := c.First(); k != nil; k, v = c.Next() {
			keys = append(keys, string(k))
			vals = append(vals, string(v))
		}
		return nil
	})
	return keys, vals, err
}

// CollectBackward traverses all key-value pairs from end to start using Cursor.Last and Cursor.Prev.
func CollectBackward(db *bolt.DB, bucketName string) ([]string, []string, error) {
	var keys []string
	var vals []string

	err := db.View(func(tx *bolt.Tx) error {
		b := tx.Bucket([]byte(bucketName))
		if b == nil {
			return errors.New("bucket not found")
		}
		c := b.Cursor()
		for k, v := c.Last(); k != nil; k, v = c.Prev() {
			keys = append(keys, string(k))
			vals = append(vals, string(v))
		}
		return nil
	})
	return keys, vals, err
}

// PrefixScan retrieves all keys starting with prefix using Cursor.Seek and Cursor.Next.
func PrefixScan(db *bolt.DB, bucketName, prefix string) ([]string, error) {
	var keys []string
	pBytes := []byte(prefix)

	err := db.View(func(tx *bolt.Tx) error {
		b := tx.Bucket([]byte(bucketName))
		if b == nil {
			return errors.New("bucket not found")
		}
		c := b.Cursor()
		for k, _ := c.Seek(pBytes); k != nil && bytes.HasPrefix(k, pBytes); k, _ = c.Next() {
			keys = append(keys, string(k))
		}
		return nil
	})
	return keys, err
}

// DeleteKeyUsingCursor seeks to a key and deletes it using Cursor.Delete in a writable transaction.
func DeleteKeyUsingCursor(db *bolt.DB, bucketName, targetKey string) error {
	return db.Update(func(tx *bolt.Tx) error {
		b := tx.Bucket([]byte(bucketName))
		if b == nil {
			return errors.New("bucket not found")
		}
		c := b.Cursor()
		k, _ := c.Seek([]byte(targetKey))
		if k == nil || string(k) != targetKey {
			return errors.New("target key not found")
		}
		return c.Delete()
	})
}

{
  "schemaVersion": 1,
  "goal": "iterate seek and delete key-value pairs with bbolt Cursor",
  "kind": "HOW",
  "packages": [
    "pkg:golang/go.etcd.io/bbolt@v1.5.0"
  ],
  "symbols": [
    "bbolt.Cursor"
  ]
}

package main

import (
	"fmt"
	"os"
	"path/filepath"

	bolt "go.etcd.io/bbolt"
	"sample"
)

func main() {
	tmpDir, err := os.MkdirTemp("", "bbolt-cursor-test-*")
	if err != nil {
		fmt.Fprintf(os.Stderr, "failed to create temp dir: %v\n", err)
		os.Exit(1)
	}
	defer os.RemoveAll(tmpDir)

	dbPath := filepath.Join(tmpDir, "cursor.db")
	db, err := sample.OpenDatabase(dbPath)
	if err != nil {
		fmt.Fprintf(os.Stderr, "failed to open database: %v\n", err)
		os.Exit(1)
	}
	defer db.Close()

	bucketName := "inventory"
	items := map[string]string{
		"item:apple":  "10",
		"item:banana": "20",
		"item:cherry": "30",
		"item:date":   "40",
		"user:alice":  "admin",
	}

	if err := sample.PopulateBucket(db, bucketName, items); err != nil {
		fmt.Fprintf(os.Stderr, "PopulateBucket failed: %v\n", err)
		os.Exit(1)
	}

	// Assertion 1: Bucket.Cursor creates a Cursor positioned at the beginning of the bucket
	err = db.View(func(tx *bolt.Tx) error {
		b := tx.Bucket([]byte(bucketName))
		if b == nil {
			return fmt.Errorf("bucket not found")
		}
		c := b.Cursor()
		if c == nil {
			return fmt.Errorf("expected cursor instance, got nil")
		}
		if c.Bucket() != b {
			return fmt.Errorf("c.Bucket() does not match parent bucket")
		}
		return nil
	})
	if err != nil {
		fmt.Fprintf(os.Stderr, "Assertion 1 failed: %v\n", err)
		os.Exit(1)
	}

	// Assertion 2: Cursor.First and Cursor.Next iterate forward through key-value pairs in lexicographical order
	fKeys, fVals, err := sample.CollectForward(db, bucketName)
	if err != nil {
		fmt.Fprintf(os.Stderr, "CollectForward failed: %v\n", err)
		os.Exit(1)
	}
	expectedForwardKeys := []string{"item:apple", "item:banana", "item:cherry", "item:date", "user:alice"}
	expectedForwardVals := []string{"10", "20", "30", "40", "admin"}
	if len(fKeys) != len(expectedForwardKeys) {
		fmt.Fprintf(os.Stderr, "Assertion 2 failed: expected %d keys, got %d\n", len(expectedForwardKeys), len(fKeys))
		os.Exit(1)
	}
	for i := range fKeys {
		if fKeys[i] != expectedForwardKeys[i] || fVals[i] != expectedForwardVals[i] {
			fmt.Fprintf(os.Stderr, "Assertion 2 failed at index %d: expected %s=%s, got %s=%s\n", i, expectedForwardKeys[i], expectedForwardVals[i], fKeys[i], fVals[i])
			os.Exit(1)
		}
	}

	// Assertion 3: Cursor.Last and Cursor.Prev iterate backward through key-value pairs
	bKeys, bVals, err := sample.CollectBackward(db, bucketName)
	if err != nil {
		fmt.Fprintf(os.Stderr, "CollectBackward failed: %v\n", err)
		os.Exit(1)
	}
	if len(bKeys) != len(expectedForwardKeys) {
		fmt.Fprintf(os.Stderr, "Assertion 3 failed: expected %d keys, got %d\n", len(expectedForwardKeys), len(bKeys))
		os.Exit(1)
	}
	for i := range bKeys {
		expectedIdx := len(expectedForwardKeys) - 1 - i
		if bKeys[i] != expectedForwardKeys[expectedIdx] || bVals[i] != expectedForwardVals[expectedIdx] {
			fmt.Fprintf(os.Stderr, "Assertion 3 failed at index %d: expected %s=%s, got %s=%s\n", i, expectedForwardKeys[expectedIdx], expectedForwardVals[expectedIdx], bKeys[i], bVals[i])
			os.Exit(1)
		}
	}

	// Assertion 4: Cursor.Seek positions the cursor at the first key greater than or equal to the target prefix
	itemKeys, err := sample.PrefixScan(db, bucketName, "item:")
	if err != nil {
		fmt.Fprintf(os.Stderr, "PrefixScan failed: %v\n", err)
		os.Exit(1)
	}
	expectedItemKeys := []string{"item:apple", "item:banana", "item:cherry", "item:date"}
	if len(itemKeys) != len(expectedItemKeys) {
		fmt.Fprintf(os.Stderr, "Assertion 4 failed: expected %d item keys, got %d\n", len(expectedItemKeys), len(itemKeys))
		os.Exit(1)
	}
	for i := range itemKeys {
		if itemKeys[i] != expectedItemKeys[i] {
			fmt.Fprintf(os.Stderr, "Assertion 4 failed at index %d: expected %s, got %s\n", i, expectedItemKeys[i], itemKeys[i])
			os.Exit(1)
		}
	}

	// Assertion 5: Cursor.Delete removes the current key-value pair under the cursor in a writable transaction
	if err := sample.DeleteKeyUsingCursor(db, bucketName, "item:banana"); err != nil {
		fmt.Fprintf(os.Stderr, "DeleteKeyUsingCursor failed: %v\n", err)
		os.Exit(1)
	}

	postDeleteKeys, _, err := sample.CollectForward(db, bucketName)
	if err != nil {
		fmt.Fprintf(os.Stderr, "CollectForward after delete failed: %v\n", err)
		os.Exit(1)
	}
	for _, k := range postDeleteKeys {
		if k == "item:banana" {
			fmt.Fprintf(os.Stderr, "Assertion 5 failed: item:banana still exists after Cursor.Delete\n")
			os.Exit(1)
		}
	}

	fmt.Println("All bbolt Cursor contract assertions passed.")
}