Refactor reader VFS API.

sqlite3reader/example_test.go

@@ -0,0 +1,95 @@
+package sqlite3reader_test
+
+import (
+	"bytes"
+	"database/sql"
+	"fmt"
+	"log"
+
+	_ "embed"
+
+	_ "github.com/ncruces/go-sqlite3/driver"
+	_ "github.com/ncruces/go-sqlite3/embed"
+	"github.com/ncruces/go-sqlite3/sqlite3reader"
+	"github.com/psanford/httpreadat"
+)
+
+//go:embed testdata/test.db
+var testDB []byte
+
+func Example_http() {
+	sqlite3reader.Create("demo.db", httpreadat.New("https://www.sanford.io/demo.db"))
+	defer sqlite3reader.Delete("demo.db")
+
+	db, err := sql.Open("sqlite3", "file:demo.db?vfs=reader")
+	if err != nil {
+		log.Fatal(err)
+	}
+	defer db.Close()
+
+	magname := map[int]string{
+		3: "thousand",
+		6: "million",
+		9: "billion",
+	}
+	rows, err := db.Query(`
+		SELECT period, data_value, magntude, units FROM csv
+			WHERE period > '2010'
+			LIMIT 10`)
+	if err != nil {
+		log.Fatal(err)
+	}
+	defer rows.Close()
+
+	for rows.Next() {
+		var period, units string
+		var value int64
+		var mag int
+		err = rows.Scan(&period, &value, &mag, &units)
+		if err != nil {
+			log.Fatal(err)
+		}
+		fmt.Printf("%s: %d %s %s\n", period, value, magname[mag], units)
+	}
+	// Output:
+	// 2010.03: 17463 million Dollars
+	// 2010.06: 17260 million Dollars
+	// 2010.09: 15419 million Dollars
+	// 2010.12: 17088 million Dollars
+	// 2011.03: 18516 million Dollars
+	// 2011.06: 18835 million Dollars
+	// 2011.09: 16390 million Dollars
+	// 2011.12: 18748 million Dollars
+	// 2012.03: 18477 million Dollars
+	// 2012.06: 18270 million Dollars
+}
+
+func Example_embed() {
+	sqlite3reader.Create("test.db", sqlite3reader.NewSizeReaderAt(bytes.NewReader(testDB)))
+	defer sqlite3reader.Delete("test.db")
+
+	db, err := sql.Open("sqlite3", "file:test.db?vfs=reader")
+	if err != nil {
+		log.Fatal(err)
+	}
+	defer db.Close()
+
+	rows, err := db.Query(`SELECT id, name FROM users`)
+	if err != nil {
+		log.Fatal(err)
+	}
+	defer rows.Close()
+
+	for rows.Next() {
+		var id, name string
+		err = rows.Scan(&id, &name)
+		if err != nil {
+			log.Fatal(err)
+		}
+		fmt.Printf("%s %s\n", id, name)
+	}
+	// Output:
+	// 0 go
+	// 1 zig
+	// 2 whatever
+}