Add child records docs and examples

pgtype/doc.go

@@ -112,6 +112,11 @@ Compatibility with database/sql
 pgtype also includes support for custom types implementing the database/sql.Scanner and database/sql/driver.Valuer
 interfaces.
 
+Child Records
+
+pgtype's support for arrays and composite records can be used to load records and their children in a single query.  See
+example_child_records_test.go for an example.
+
 Overview of Scanning Implementation
 
 The first step is to use the OID to lookup the correct Codec. If the OID is unavailable, Map will try to find the OID

pgtype/example_child_records_test.go

@@ -0,0 +1,90 @@
+package pgtype_test
+
+import (
+	"context"
+	"fmt"
+	"os"
+	"time"
+
+	"github.com/jackc/pgx/v5"
+)
+
+// This example uses a single query to return parent and child records.
+func Example_childRecords() {
+	ctx, cancel := context.WithTimeout(context.Background(), 15*time.Second)
+	defer cancel()
+
+	conn, err := pgx.Connect(ctx, os.Getenv("PGX_TEST_DATABASE"))
+	if err != nil {
+		fmt.Printf("Unable to establish connection: %v", err)
+		return
+	}
+
+	// Setup example schema and data.
+	_, err = conn.Exec(ctx, `
+create temporary table teams (
+	name text primary key
+);
+
+create temporary table players (
+	name text primary key,
+	team_name text,
+	position text
+);
+
+insert into teams (name) values
+	('Alpha'),
+	('Beta');
+
+insert into players (name, team_name, position) values
+	('Adam', 'Alpha', 'wing'),
+	('Bill', 'Alpha', 'halfback'),
+	('Charlie', 'Alpha', 'fullback'),
+	('Don', 'Beta', 'halfback'),
+	('Edgar', 'Beta', 'halfback'),
+	('Frank', 'Beta', 'fullback')
+`)
+	if err != nil {
+		fmt.Printf("Unable to setup example schema and data: %v", err)
+		return
+	}
+
+	type Player struct {
+		Name     string
+		Position string
+	}
+
+	type Team struct {
+		Name    string
+		Players []Player
+	}
+
+	rows, _ := conn.Query(ctx, `
+select t.name,
+	(select array_agg(row(p.name, position) order by p.name) from players p where p.team_name = t.name)
+from teams t
+order by t.name
+`)
+	teams, err := pgx.CollectRows(rows, pgx.RowToStructByPos[Team])
+	if err != nil {
+		fmt.Printf("CollectRows error: %v", err)
+		return
+	}
+
+	for _, team := range teams {
+		fmt.Println(team.Name)
+		for _, player := range team.Players {
+			fmt.Printf("  %s: %s\n", player.Name, player.Position)
+		}
+	}
+
+	// Output:
+	// Alpha
+	//   Adam: wing
+	//   Bill: halfback
+	//   Charlie: fullback
+	// Beta
+	//   Don: halfback
+	//   Edgar: halfback
+	//   Frank: fullback
+}

pgtype/example_custom_type_test.go

@@ -39,7 +39,7 @@ func (src *Point) String() string {
 	return fmt.Sprintf("%.1f, %.1f", src.X, src.Y)
 }
 
-func Example_CustomType() {
+func Example_customType() {
 	conn, err := pgx.Connect(context.Background(), os.Getenv("PGX_TEST_DATABASE"))
 	if err != nil {
 		fmt.Printf("Unable to establish connection: %v", err)

pgtype/example_json_test.go

@@ -8,7 +8,7 @@ import (
 	"github.com/jackc/pgx/v5"
 )
 
-func Example_JSON() {
+func Example_json() {
 	conn, err := pgx.Connect(context.Background(), os.Getenv("PGX_TEST_DATABASE"))
 	if err != nil {
 		fmt.Printf("Unable to establish connection: %v", err)