github.com/jackc/pgx/v5 v5.10.0: pgx.CopyFromRows, pgx.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 pgx.CopyFromRows and pgx.CopyFromSlice in 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
Demonstrate these symbols/APIs:
  - pgx.CopyFromRows
  - pgx.CopyFromSlice
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:f2760af217973852938518f78bdcf19cad9f9f7fb909390410a88e50e254eff6","contract":["pgx.CopyFromRows iterates over row slices and returns matching values","pgx.CopyFromRows returns false on Next when rows slice is empty","pgx.CopyFromSlice generates rows using an index callback function","pgx.CopyFromSlice handles empty slice by returning false immediately","pgx.CopyFromSlice captures and propagates errors returned by callback to Values and Err"],"goal":"verify pgx.CopyFromRows and pgx.CopyFromSlice in 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":["pgx.CopyFromRows","pgx.CopyFromSlice"]},"contractCommand":["go","run","./test"],"environment":{"arch":"x64","ecosystem":"golang","os":"windows","osVersionBucket":"11","packageManager":"go","schemaVersion":1},"license":"MIT-0","packages":["pkg:golang/github.com/jackc/pgx/v5@v5.10.0"],"schemaVersion":1,"symbols":["pgx.CopyFromRows","pgx.CopyFromSlice"],"verifierAdapter":"golang@1"}

module sample

go 1.26.5

require github.com/jackc/pgx/v5 v5.10.0

require (
	github.com/jackc/pgpassfile v1.0.0 // indirect
	github.com/jackc/pgservicefile v0.0.0-20240606120523-5a60cdf6a761 // 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/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/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/jackc/puddle/v2 v2.2.2 h1:PR8nw+E/1w0GLuRFSmiioY6UooMp6KJv0/61nB7icHo=
github.com/jackc/puddle/v2 v2.2.2/go.mod h1:vriiEXHvEE654aYKXXjOvZM39qJ0q+azkZFrfEOc3H4=
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/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=
github.com/stretchr/testify v1.11.1 h1:7s2iGBzp5EwR7/aIZr8ao5+dra3wiQyKjjFuvgVKu7U=
github.com/stretchr/testify v1.11.1/go.mod h1:wZwfW3scLgRK+23gO65QZefKpKQRnfz6sD981Nm4B6U=
golang.org/x/sync v0.17.0 h1:l60nONMj9l5drqw6jlhIELNv9I0A4OFgRsG9k2oT9Ug=
golang.org/x/sync v0.17.0/go.mod h1:9KTHXmSnoGruLpwFjVSX0lNNA75CykiMECbovNTZqGI=
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=
gopkg.in/yaml.v3 v3.0.1 h1:fxVm/GzAzEWqLHuvctI91KS9hhNmmWOoWu0XTYJS7CA=
gopkg.in/yaml.v3 v3.0.1/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=

package main

import (
	"fmt"

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

// User represents a sample domain record to be bulk copied.
type User struct {
	ID   int64
	Name string
	Role string
}

func main() {
	// 1. Demonstrate pgx.CopyFromRows with raw slices
	rawRows := [][]any{
		{int64(1), "Alice", "admin"},
		{int64(2), "Bob", "member"},
	}
	rowsSource := pgx.CopyFromRows(rawRows)
	fmt.Printf("Created CopyFromRows source: %T\n", rowsSource)

	// 2. Demonstrate pgx.CopyFromSlice with domain structs
	users := []User{
		{ID: 101, Name: "Charlie", Role: "engineer"},
		{ID: 102, Name: "Diana", Role: "designer"},
	}
	sliceSource := pgx.CopyFromSlice(len(users), func(i int) ([]any, error) {
		return []any{users[i].ID, users[i].Name, users[i].Role}, nil
	})
	fmt.Printf("Created CopyFromSlice source: %T\n", sliceSource)
}

{
  "schemaVersion": 1,
  "goal": "verify pgx.CopyFromRows and pgx.CopyFromSlice in pkg:golang/github.com/jackc/pgx/v5@v5.10.0",
  "kind": "HOW",
  "packages": [
    "pkg:golang/github.com/jackc/pgx/v5@v5.10.0"
  ],
  "symbols": [
    "pgx.CopyFromRows",
    "pgx.CopyFromSlice"
  ],
  "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"
)

func assertTrue(name string, condition bool) {
	if !condition {
		fmt.Fprintf(os.Stderr, "Assertion failed for %s: expected true, got false\n", name)
		os.Exit(1)
	}
}

func assertEqualInt(name string, actual, expected int) {
	if actual != expected {
		fmt.Fprintf(os.Stderr, "Assertion failed for %s: got %d, expected %d\n", name, actual, expected)
		os.Exit(1)
	}
}

func assertEqualInt64(name string, actual, expected int64) {
	if actual != expected {
		fmt.Fprintf(os.Stderr, "Assertion failed for %s: got %d, expected %d\n", name, actual, expected)
		os.Exit(1)
	}
}

func assertEqualString(name, actual, expected string) {
	if actual != expected {
		fmt.Fprintf(os.Stderr, "Assertion failed for %s: got %q, expected %q\n", name, actual, expected)
		os.Exit(1)
	}
}

type User struct {
	ID   int64
	Name string
	Role string
}

func main() {
	// Contract: pgx.CopyFromRows iterates over row slices and returns matching values
	rawRows := [][]any{
		{int64(1), "Alice", "admin"},
		{int64(2), "Bob", "member"},
	}
	srcRows := pgx.CopyFromRows(rawRows)

	assertTrue("CopyFromRows row 1 Next returns true", srcRows.Next())
	vals1, err1 := srcRows.Values()
	assertTrue("CopyFromRows row 1 Values returns nil error", err1 == nil)
	assertEqualInt("CopyFromRows row 1 len is 3", len(vals1), 3)
	assertEqualInt64("CopyFromRows row 1 ID", vals1[0].(int64), 1)
	assertEqualString("CopyFromRows row 1 Name", vals1[1].(string), "Alice")
	assertEqualString("CopyFromRows row 1 Role", vals1[2].(string), "admin")

	assertTrue("CopyFromRows row 2 Next returns true", srcRows.Next())
	vals2, err2 := srcRows.Values()
	assertTrue("CopyFromRows row 2 Values returns nil error", err2 == nil)
	assertEqualInt("CopyFromRows row 2 len is 3", len(vals2), 3)
	assertEqualInt64("CopyFromRows row 2 ID", vals2[0].(int64), 2)
	assertEqualString("CopyFromRows row 2 Name", vals2[1].(string), "Bob")
	assertEqualString("CopyFromRows row 2 Role", vals2[2].(string), "member")

	assertTrue("CopyFromRows end Next returns false", !srcRows.Next())
	assertTrue("CopyFromRows Err returns nil", srcRows.Err() == nil)

	// Contract: pgx.CopyFromRows returns false on Next when rows slice is empty
	srcEmptyRows := pgx.CopyFromRows(nil)
	assertTrue("CopyFromRows nil Next returns false", !srcEmptyRows.Next())
	assertTrue("CopyFromRows nil Err returns nil", srcEmptyRows.Err() == nil)

	srcEmptySliceRows := pgx.CopyFromRows([][]any{})
	assertTrue("CopyFromRows empty slice Next returns false", !srcEmptySliceRows.Next())
	assertTrue("CopyFromRows empty slice Err returns nil", srcEmptySliceRows.Err() == nil)

	// Contract: pgx.CopyFromSlice generates rows using an index callback function
	users := []User{
		{ID: 101, Name: "Charlie", Role: "engineer"},
		{ID: 102, Name: "Diana", Role: "designer"},
	}
	srcSlice := pgx.CopyFromSlice(len(users), func(i int) ([]any, error) {
		return []any{users[i].ID, users[i].Name, users[i].Role}, nil
	})

	assertTrue("CopyFromSlice item 1 Next returns true", srcSlice.Next())
	sliceVals1, sliceErr1 := srcSlice.Values()
	assertTrue("CopyFromSlice item 1 Values returns nil error", sliceErr1 == nil)
	assertEqualInt("CopyFromSlice item 1 len is 3", len(sliceVals1), 3)
	assertEqualInt64("CopyFromSlice item 1 ID", sliceVals1[0].(int64), 101)
	assertEqualString("CopyFromSlice item 1 Name", sliceVals1[1].(string), "Charlie")
	assertEqualString("CopyFromSlice item 1 Role", sliceVals1[2].(string), "engineer")

	assertTrue("CopyFromSlice item 2 Next returns true", srcSlice.Next())
	sliceVals2, sliceErr2 := srcSlice.Values()
	assertTrue("CopyFromSlice item 2 Values returns nil error", sliceErr2 == nil)
	assertEqualInt("CopyFromSlice item 2 len is 3", len(sliceVals2), 3)
	assertEqualInt64("CopyFromSlice item 2 ID", sliceVals2[0].(int64), 102)
	assertEqualString("CopyFromSlice item 2 Name", sliceVals2[1].(string), "Diana")
	assertEqualString("CopyFromSlice item 2 Role", sliceVals2[2].(string), "designer")

	assertTrue("CopyFromSlice end Next returns false", !srcSlice.Next())
	assertTrue("CopyFromSlice Err returns nil", srcSlice.Err() == nil)

	// Contract: pgx.CopyFromSlice handles empty slice by returning false immediately
	srcSliceEmpty := pgx.CopyFromSlice(0, func(i int) ([]any, error) {
		return nil, nil
	})
	assertTrue("CopyFromSlice empty Next returns false", !srcSliceEmpty.Next())
	assertTrue("CopyFromSlice empty Err returns nil", srcSliceEmpty.Err() == nil)

	// Contract: pgx.CopyFromSlice captures and propagates errors returned by callback to Values and Err
	customErr := errors.New("data conversion failed at index 1")
	srcSliceErr := pgx.CopyFromSlice(2, func(i int) ([]any, error) {
		if i == 1 {
			return nil, customErr
		}
		return []any{i, "valid"}, nil
	})

	assertTrue("CopyFromSlice err source item 0 Next returns true", srcSliceErr.Next())
	errVals0, err0 := srcSliceErr.Values()
	assertTrue("CopyFromSlice err source item 0 returns nil error", err0 == nil)
	assertEqualInt("CopyFromSlice err source item 0 value", errVals0[0].(int), 0)

	assertTrue("CopyFromSlice err source item 1 Next returns true", srcSliceErr.Next())
	_, err1Val := srcSliceErr.Values()
	assertTrue("CopyFromSlice err source item 1 Values returns customErr", errors.Is(err1Val, customErr))
	assertTrue("CopyFromSlice err source Err returns customErr", errors.Is(srcSliceErr.Err(), customErr))
	assertTrue("CopyFromSlice end Next returns false", !srcSliceErr.Next())

	fmt.Println("All pgx.CopyFrom contract assertions passed successfully.")
}