github.com/jackc/pgx/v5 v5.10.0: CopyFromFunc, CopyFromRows, CopyFromSlice

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: verify pkg:golang/github.com/jackc/pgx/v5@v5.10.0
Kind: HOW

Use EXACTLY these public packages and versions:
  - pkg:golang/github.com/jackc/pgx/v5@v5.10.0
Constraints:
  - executionContext: node
Required runtime conditions:
  - ecosystem: npm
  - language: javascript
  - moduleSystem: cjs
  - packageManager: npm@11.8.0
  - runtime: node@24.13.1

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:sha256:5f0375635e79de1407c6eb35323c5ab1b9a52370612f5db9a4fd65260b3c1083","contract":["pgx.CopyFromRows wraps raw row matrix into CopyFromSource with sequential Next and Values access","pgx.CopyFromRows yields false on Next after all rows are consumed without errors","pgx.CopyFromSlice generates row values from index generator function for specified length","pgx.CopyFromSlice records error in Values and exposes it via Err when index generator fails","pgx.CopyFromFunc streams row values sequentially until receiving nil row and nil error","pgx.CopyFromFunc terminates iteration on Next and exposes error via Err when stream generator fails"],"goal":"verify pkg:golang/github.com/jackc/pgx/v5@v5.10.0","kind":"HOW","packages":["pkg:golang/github.com/jackc/pgx/v5@v5.10.0"],"schemaVersion":1,"symbols":["github.com/jackc/pgx/v5.CopyFromFunc","github.com/jackc/pgx/v5.CopyFromRows","github.com/jackc/pgx/v5.CopyFromSlice","github.com/jackc/pgx/v5.CopyFromSource"]},"contractCommand":["go","run","./test"],"environment":{"arch":"x64","ecosystem":"golang","language":"go","moduleSystem":"go","os":"windows","osVersionBucket":"11","packageManager":"go","packageManagerVersion":"1.26.5","runtime":"go","runtimeVersion":"1.26.5","schemaVersion":1},"license":"MIT-0","packages":["pkg:golang/github.com/jackc/pgx/v5@v5.10.0"],"schemaVersion":1,"symbols":["github.com/jackc/pgx/v5.CopyFromFunc","github.com/jackc/pgx/v5.CopyFromRows","github.com/jackc/pgx/v5.CopyFromSlice","github.com/jackc/pgx/v5.CopyFromSource"],"verifierAdapter":"golang@1"}

module sample

go 1.26.5

require (
	github.com/jackc/pgpassfile v1.0.0 // indirect
	github.com/jackc/pgservicefile v0.0.0-20240606120523-5a60cdf6a761 // indirect
	github.com/jackc/pgx/v5 v5.10.0 // indirect
	golang.org/x/text v0.29.0 // indirect
)

github.com/davecgh/go-spew v1.1.0/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
github.com/jackc/pgpassfile v1.0.0 h1:/6Hmqy13Ss2zCq62VdNG8tM1wchn8zjSGOBJ6icpsIM=
github.com/jackc/pgpassfile v1.0.0/go.mod h1:CEx0iS5ambNFdcRtxPj5JhEz+xB6uRky5eyVu/W2HEg=
github.com/jackc/pgservicefile v0.0.0-20240606120523-5a60cdf6a761 h1:iCEnooe7UlwOQYpKFhBabPMi4aNAfoODPEFNiAnClxo=
github.com/jackc/pgservicefile v0.0.0-20240606120523-5a60cdf6a761/go.mod h1:5TJZWKEWniPve33vlWYSoGYefn3gLQRzjfDlhSJ9ZKM=
github.com/jackc/pgx/v5 v5.10.0 h1:VhSvgU2jSli8o3AqIEOTJr7rZwAEUVo4E4XhR94Zfr0=
github.com/jackc/pgx/v5 v5.10.0/go.mod h1:mal1tBGAFfLHvZzaYh77YS/eC6IX9OWbRV1QIIM0Jn4=
github.com/pmezard/go-difflib v1.0.0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4=
github.com/stretchr/objx v0.1.0/go.mod h1:HFkY916IF+rwdDfMAkV7OtwuqBVzrE8GR6GFx+wExME=
github.com/stretchr/testify v1.3.0/go.mod h1:M5WIy9Dh21IEIfnGCwXGc5bZfKNJtfHm1UVUgZn+9EI=
github.com/stretchr/testify v1.7.0/go.mod h1:6Fq8oRcR53rry900zMqJjRRixrwX3KX962/h/Wwjteg=
golang.org/x/text v0.29.0 h1:1neNs90w9YzJ9BocxfsQNHKuAT4pkghyXc4nhZ6sJvk=
golang.org/x/text v0.29.0/go.mod h1:7MhJOA9CD2qZyOKYazxdYMF85OwPdEr9jTtBpO7ydH4=
gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
gopkg.in/yaml.v3 v3.0.0-20200313102051-9f266ea9e77c/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=

package main

import (
	"fmt"

	"github.com/jackc/pgx/v5"
)

// User represents a sample record for bulk copy operations.
type User struct {
	ID   int
	Name string
	Role string
}

func main() {
	// 1. CopyFromRows: wrap 2D slice of values
	rawRows := [][]any{
		{1, "Alice", "admin"},
		{2, "Bob", "developer"},
	}
	sourceRows := pgx.CopyFromRows(rawRows)
	fmt.Println("Iterating pgx.CopyFromRows:")
	for sourceRows.Next() {
		values, err := sourceRows.Values()
		if err != nil {
			panic(err)
		}
		fmt.Printf("  row: %v\n", values)
	}

	// 2. CopyFromSlice: adapt typed slice with generator function
	users := []User{
		{ID: 3, Name: "Charlie", Role: "designer"},
		{ID: 4, Name: "Diana", Role: "tester"},
	}
	sourceSlice := pgx.CopyFromSlice(len(users), func(i int) ([]any, error) {
		return []any{users[i].ID, users[i].Name, users[i].Role}, nil
	})
	fmt.Println("Iterating pgx.CopyFromSlice:")
	for sourceSlice.Next() {
		values, err := sourceSlice.Values()
		if err != nil {
			panic(err)
		}
		fmt.Printf("  row: %v\n", values)
	}

	// 3. CopyFromFunc: dynamically stream rows until nil, nil
	counter := 5
	sourceFunc := pgx.CopyFromFunc(func() ([]any, error) {
		if counter > 6 {
			return nil, nil // signals end of stream
		}
		row := []any{counter, fmt.Sprintf("StreamUser%d", counter), "guest"}
		counter++
		return row, nil
	})
	fmt.Println("Iterating pgx.CopyFromFunc:")
	for sourceFunc.Next() {
		values, err := sourceFunc.Values()
		if err != nil {
			panic(err)
		}
		fmt.Printf("  row: %v\n", values)
	}
}

{
  "schemaVersion": 1,
  "goal": "verify pkg:golang/github.com/jackc/pgx/v5@v5.10.0",
  "kind": "HOW",
  "packages": [
    "pkg:golang/github.com/jackc/pgx/v5@v5.10.0"
  ],
  "constraints": {
    "executionContext": "node"
  },
  "runtimeConditions": {
    "ecosystem": "npm",
    "language": "javascript",
    "moduleSystem": "cjs",
    "packageManager": "npm@11.8.0",
    "runtime": "node@24.13.1"
  }
}

package main

import (
	"errors"
	"fmt"
	"os"

	"github.com/jackc/pgx/v5"
)

type User struct {
	ID   int
	Name string
}

func main() {
	// Assertion 1: pgx.CopyFromRows wraps raw row matrix into CopyFromSource with sequential Next and Values access
	matrix := [][]any{
		{101, "Alpha"},
		{102, "Beta"},
	}
	srcRows := pgx.CopyFromRows(matrix)
	if !srcRows.Next() {
		fmt.Fprintf(os.Stderr, "FAIL: expected Next() to return true on first row\n")
		os.Exit(1)
	}
	v1, err := srcRows.Values()
	if err != nil || len(v1) != 2 || v1[0] != 101 || v1[1] != "Alpha" {
		fmt.Fprintf(os.Stderr, "FAIL: first row values mismatch: %v (err: %v)\n", v1, err)
		os.Exit(1)
	}
	if !srcRows.Next() {
		fmt.Fprintf(os.Stderr, "FAIL: expected Next() to return true on second row\n")
		os.Exit(1)
	}
	v2, err := srcRows.Values()
	if err != nil || len(v2) != 2 || v2[0] != 102 || v2[1] != "Beta" {
		fmt.Fprintf(os.Stderr, "FAIL: second row values mismatch: %v (err: %v)\n", v2, err)
		os.Exit(1)
	}

	// Assertion 2: pgx.CopyFromRows yields false on Next after all rows are consumed without errors
	if srcRows.Next() {
		fmt.Fprintf(os.Stderr, "FAIL: expected Next() to return false after matrix exhausted\n")
		os.Exit(1)
	}
	if srcRows.Err() != nil {
		fmt.Fprintf(os.Stderr, "FAIL: expected Err() to be nil, got: %v\n", srcRows.Err())
		os.Exit(1)
	}

	// Assertion 3: pgx.CopyFromSlice generates row values from index generator function for specified length
	users := []User{
		{ID: 201, Name: "Gamma"},
		{ID: 202, Name: "Delta"},
		{ID: 203, Name: "Epsilon"},
	}
	srcSlice := pgx.CopyFromSlice(len(users), func(i int) ([]any, error) {
		return []any{users[i].ID, users[i].Name}, nil
	})
	var sliceCollected [][]any
	for srcSlice.Next() {
		vals, err := srcSlice.Values()
		if err != nil {
			fmt.Fprintf(os.Stderr, "FAIL: CopyFromSlice Values returned unexpected error: %v\n", err)
			os.Exit(1)
		}
		sliceCollected = append(sliceCollected, vals)
	}
	if srcSlice.Err() != nil {
		fmt.Fprintf(os.Stderr, "FAIL: CopyFromSlice Err returned unexpected error: %v\n", srcSlice.Err())
		os.Exit(1)
	}
	if len(sliceCollected) != 3 || sliceCollected[0][0] != 201 || sliceCollected[2][1] != "Epsilon" {
		fmt.Fprintf(os.Stderr, "FAIL: CopyFromSlice collected data mismatch: %v\n", sliceCollected)
		os.Exit(1)
	}

	// Assertion 4: pgx.CopyFromSlice records error in Values and exposes it via Err when index generator fails
	genErr := errors.New("generator failed on index 2")
	srcSliceErr := pgx.CopyFromSlice(5, func(i int) ([]any, error) {
		if i == 2 {
			return nil, genErr
		}
		return []any{i, "name"}, nil
	})
	processed := 0
	for srcSliceErr.Next() {
		_, err := srcSliceErr.Values()
		if err != nil {
			break
		}
		processed++
	}
	if !errors.Is(srcSliceErr.Err(), genErr) {
		fmt.Fprintf(os.Stderr, "FAIL: expected generator error %v, got: %v\n", genErr, srcSliceErr.Err())
		os.Exit(1)
	}
	if processed != 2 {
		fmt.Fprintf(os.Stderr, "FAIL: expected 2 rows processed before error, got: %d\n", processed)
		os.Exit(1)
	}

	// Assertion 5: pgx.CopyFromFunc streams row values sequentially until receiving nil row and nil error
	streamCount := 0
	srcFunc := pgx.CopyFromFunc(func() ([]any, error) {
		if streamCount >= 3 {
			return nil, nil // signal end of stream
		}
		streamCount++
		return []any{streamCount, fmt.Sprintf("val%d", streamCount)}, nil
	})
	var funcCollected [][]any
	for srcFunc.Next() {
		vals, err := srcFunc.Values()
		if err != nil {
			fmt.Fprintf(os.Stderr, "FAIL: CopyFromFunc Values returned unexpected error: %v\n", err)
			os.Exit(1)
		}
		funcCollected = append(funcCollected, vals)
	}
	if srcFunc.Err() != nil {
		fmt.Fprintf(os.Stderr, "FAIL: CopyFromFunc Err returned unexpected error: %v\n", srcFunc.Err())
		os.Exit(1)
	}
	if len(funcCollected) != 3 || funcCollected[0][0] != 1 || funcCollected[2][0] != 3 {
		fmt.Fprintf(os.Stderr, "FAIL: CopyFromFunc collected data mismatch: %v\n", funcCollected)
		os.Exit(1)
	}

	// Assertion 6: pgx.CopyFromFunc terminates iteration on Next and exposes error via Err when stream generator fails
	streamErr := errors.New("stream producer error")
	srcFuncErr := pgx.CopyFromFunc(func() ([]any, error) {
		return nil, streamErr
	})
	if srcFuncErr.Next() {
		fmt.Fprintf(os.Stderr, "FAIL: CopyFromFunc Next returned true on immediate error\n")
		os.Exit(1)
	}
	if !errors.Is(srcFuncErr.Err(), streamErr) {
		fmt.Fprintf(os.Stderr, "FAIL: expected stream error %v, got: %v\n", streamErr, srcFuncErr.Err())
		os.Exit(1)
	}

	fmt.Println("PASS: all contract assertions passed for pkg:golang/github.com/jackc/pgx/v5@v5.10.0")
}