Towards virtual tables.

vtab_test.go

@@ -0,0 +1,67 @@
+package sqlite3_test
+
+import (
+	"log"
+
+	"github.com/ncruces/go-sqlite3"
+	_ "github.com/ncruces/go-sqlite3/embed"
+)
+
+func ExampleCreateModule() {
+	db, err := sqlite3.Open(":memory:")
+	if err != nil {
+		log.Fatal(err)
+	}
+	defer db.Close()
+
+	err = sqlite3.CreateModule(db, "generate_series", seriesModule{})
+	if err != nil {
+		log.Fatal(err)
+	}
+
+	stmt, _, err := db.Prepare(`SELECT value FROM generate_series(5,100,5)`)
+	if err != nil {
+		log.Fatal(err)
+	}
+	defer stmt.Close()
+
+	// Output:
+}
+
+type seriesModule struct{}
+
+func (seriesModule) Connect(c *sqlite3.Conn, arg ...string) (*seriesTable, error) {
+	err := c.DeclareVtab(`CREATE TABLE x(value, start HIDDEN, stop HIDDEN, step HIDDEN)`)
+	if err != nil {
+		return nil, err
+	}
+	return &seriesTable{0, 0, 1}, nil
+}
+
+type seriesTable struct {
+	start int64
+	stop  int64
+	step  int64
+}
+
+func (*seriesTable) Disconnect() error {
+	return nil
+}
+
+func (*seriesTable) BestIndex(idx *sqlite3.IndexInfo) error {
+	idx.IdxNum = 0
+	idx.IdxStr = "default"
+	argv := 1
+	for i, cst := range idx.Constraint {
+		if cst.Usable && cst.Op == sqlite3.Eq {
+			idx.ConstraintUsage[i] = sqlite3.IndexConstraintUsage{
+				ArgvIndex: argv,
+				Omit:      true,
+			}
+			argv++
+		}
+	}
+	return nil
+}
+
+func (*seriesTable) Open() (sqlite3.VTabCursor, error) { return nil, nil }