Complete example with revised structure.

examples/batch/batch.go

@@ -4,114 +4,112 @@ import (
 	"context"
 	"errors"
 	"fmt"
-	"net/http"
-	"strings"
 
 	pgx "github.com/jackc/pgx/v5"
 	pgconn "github.com/jackc/pgx/v5/pgconn"
 	pgxpool "github.com/jackc/pgx/v5/pgxpool"
 )
 
 type PgxPoolInterface interface {
-	Begin(context.Context) (pgx.Tx, error)
 	Exec(context.Context, string, ...interface{}) (pgconn.CommandTag, error)
 	SendBatch(context.Context, *pgx.Batch) pgx.BatchResults
 	Close()
 }
 
-type ExampleBatch struct {
-	batch  *pgx.Batch
-	br     pgx.BatchResults
-	db     PgxPoolInterface
-	output strings.Builder
+type exampleBatch struct {
+	batch   *pgx.Batch       // batch pointer
+	results pgx.BatchResults // query results
+	db      PgxPoolInterface // database connection
 }
 
-func (ex *ExampleBatch) insertRow(fields ...string) (err error) {
-	for i, value := range fields {
-		fields[i] = "$$" + value + "$$"
-	}
-	sql := `INSERT INTO metadata (title, authors, subject, description)
-	VALUES 
-	(` + strings.Join(fields[:4], ", ") + ");"
-	_, err = ex.db.Exec(context.Background(), sql)
-	return err
+type metadata struct {
+	title       string
+	authors     string
+	subject     string
+	description string
 }
 
-func (ex *ExampleBatch) databaseSetup() (err error) {
-	// Create a new table 'metadata'
-	sql := `
-	CREATE TABLE IF NOT EXISTS metadata (
+func NewExample(db PgxPoolInterface) (example exampleBatch, err error) {
+
+	example = exampleBatch{
+		db:    db,           // database
+		batch: &pgx.Batch{}, // batch struct address
+	}
+
+	sql := `CREATE TABLE IF NOT EXISTS metadata (
 	id BIGINT PRIMARY KEY GENERATED BY DEFAULT AS IDENTITY,
 	title TEXT NOT NULL,
 	authors TEXT NOT NULL,
 	subject TEXT NOT NULL,
 	description TEXT NOT NULL);
-	DELETE FROM metadata ;
-	INSERT INTO metadata (title, authors, subject, description)
-	VALUES
-		($$A Journey Through the Alps$$, $$John Doe, Jane Smith$$, $$Hiking, Nature, Travel$$, $$Explore the breathtaking beauty of the Alps on a scenic hiking adventure. Discover hidden trails, alpine lakes, and charming mountain villages.$$),
-		($$The Art of Baking: A Beginner's Guide$$, $$Emily Baker$$, $$Cooking, Baking, Food$$, $$Learn the fundamentals of baking and create delicious treats from scratch. Master techniques like kneading dough, frosting cakes, and piping cookies.$$),
-		($$The History of Ancient Rome$$, $$David Johnson$$, $$History, Ancient Rome, Civilization$$, $$Delve into the fascinating history of the Roman Empire. Explore its rise to power, its cultural achievements, and its eventual decline.$$);
-	`
-	_, err = ex.db.Exec(context.Background(), sql)
-	return err
-}
-
-func (ex *ExampleBatch) printResults(w http.ResponseWriter, req *http.Request) {
+	DELETE FROM metadata ;`
+	_, err = example.db.Exec(context.Background(), sql) // Execute sql
 
-	var temp strings.Builder
-
-	// Iterate over a batch of queued queries
-	for _, query := range ex.batch.QueuedQueries {
-
-		// Read results from the current query
-		rows, _ := ex.br.Query()
-
-		// Print SQL field of the current query
-		temp.WriteString(fmt.Sprintf("%v \n", query.SQL))
+	return example, err
+}
 
-		// Iterate over the selected records
-		//
-		for rows.Next() {
-			err := rows.Err()
-			if err != nil {
-				return
-			}
-
-			values, err := rows.Values()
-			if err != nil {
-				return
-			}
-
-			// Convert values to a string
-			temp.WriteString(fmt.Sprintf("%v \n", values))
+func (ex *exampleBatch) BulkInsertMetadata(data []metadata) error {
+	query := `INSERT INTO metadata (title, authors, subject, description)
+	VALUES
+		(@title, @authors, @subject, @description)
+	`
+	batch := &pgx.Batch{}
+	for _, m := range data {
+		args := pgx.NamedArgs{
+			"title":       m.title,
+			"authors":     m.authors,
+			"subject":     m.subject,
+			"description": m.description,
 		}
+		batch.Queue(query, args)
 	}
 
-	if ex.output.Len() == 0 {
-		ex.output = temp
+	results := ex.db.SendBatch(context.Background(), batch)
+	defer results.Close()
+
+	for index := range data {
+		_, err := results.Exec()
+		if err != nil {
+			return fmt.Errorf("unable to insert row %d: %w", index, err)
+		}
 	}
-	fmt.Fprint(w, ex.output.String())
 
+	return results.Close()
 }
 
-func (ex *ExampleBatch) requestBatch() (err error) {
+func (ex *exampleBatch) SendCustomBatch(queries []string) (err error) {
+
+	// Add SQL queries to the queue for a custom batch
+	for _, query := range queries {
+		ex.batch.Queue(query)
+	}
 
 	// Efficiently transmits queued queries as a single transaction.
 	// After the queries are run, a BatchResults object is returned.
-	//
-	ex.br = ex.db.SendBatch(context.Background(), ex.batch)
-	if ex.br == nil {
+	ex.results = ex.db.SendBatch(context.Background(), ex.batch)
+	if ex.results == nil {
 		return errors.New("SendBatch returns a NIL object")
 	}
 
 	return err
 }
 
-func (ex *ExampleBatch) Close() (err error) {
+func (ex *exampleBatch) TestCustomResults() (err error) {
+
+	for index := range ex.batch.QueuedQueries {
+		_, err := ex.results.Exec()
+		if err != nil {
+			return fmt.Errorf("unable to run query %d: %w", index, err)
+		}
+	}
+
+	return ex.results.Close()
+}
+
+func (ex *exampleBatch) Close() (err error) {
 
 	// Close batch results object
-	ex.br.Close()
+	ex.results.Close()
 
 	// Close connection to database
 	ex.db.Close()
@@ -122,41 +120,36 @@ func (ex *ExampleBatch) Close() (err error) {
 func main() {
 
 	// @NOTE: the real connection is not required for tests
-	db, err := pgxpool.New(context.Background(), "postgres://postgres:password@localhost/batch")
-	if err != nil {
-		panic(err)
-	}
+	db, _ := pgxpool.New(context.Background(), "postgres://postgres:password@localhost/batch")
 
-	// Setup the database
-	var example = ExampleBatch{
-		db:    db,
-		batch: &pgx.Batch{},
-	}
-	if err = example.databaseSetup(); err != nil {
+	// Create a new instance of example struct
+	example, err := NewExample(db)
+	if err != nil {
 		panic(err)
 	}
 	defer example.Close()
 
-	// Add an example to database table
-	example.insertRow(
-		"The Adventures of Captain Pickle",
-		"Timothy T. Turtle",
-		"Adventure, Fantasy",
-		"Join Captain Pickle...",
-	)
-
-	// Add SQL queries to the queue for a batch operation
-	example.batch.Queue("SELECT title FROM metadata")
-	example.batch.Queue("SELECT authors FROM metadata")
-	example.batch.Queue("SELECT subject, description FROM metadata")
-
-	// Send the batch request to database
-	if err = example.requestBatch(); err != nil {
-		panic(err)
+	// Insert multiple rows into the database
+	example.BulkInsertMetadata([]metadata{
+		{`A Journey Through the Alps`, `John Doe, Jane Smith`, `Hiking, Nature, Travel`, `Explore the breathtaking beauty of the Alps on a scenic hiking adventure. Discover hidden trails, alpine lakes, and charming mountain villages.`},
+		{`The Art of Baking: A Beginner's Guide`, `Emily Baker`, `Cooking, Baking, Food`, `Learn the fundamentals of baking and create delicious treats from scratch. Master techniques like kneading dough, frosting cakes, and piping cookies.`},
+		{`The History of Ancient Rome`, `David Johnson`, `History, Ancient Rome, Civilization`, `Delve into the fascinating history of the Roman Empire. Explore its rise to power, its cultural achievements, and its eventual decline.`},
+	})
+
+	// Send a custom batch operation to database
+	example.SendCustomBatch([]string{
+		"SELECT title FROM metadata",
+		"SELECT authors FROM metadata",
+		"SELECT subject, description FROM metadata",
+	})
+
+	// Print batch results
+	for _, query := range example.batch.QueuedQueries {
+		fmt.Println(query.SQL)
+		rows, _ := example.results.Query()
+		for rows.Next() {
+			values, _ := rows.Values()
+			fmt.Println(values)
+		}
 	}
-
-	// Print batch result to ...
-	http.HandleFunc("/", example.printResults)
-	_ = http.ListenAndServe(":8080", nil)
-
 }