Array extension.

ext/array/array.go

@@ -0,0 +1,140 @@
+// Package array provides the array table-valued SQL function.
+package array
+
+import (
+	"fmt"
+	"reflect"
+
+	"github.com/ncruces/go-sqlite3"
+)
+
+// Register registers the single-argument array table-valued SQL function.
+// The argument must be an [sqlite3.Pointer] to a Go slice or array
+// of ints, floats, bools, strings or blobs.
+//
+// https://sqlite.org/carray.html
+func Register(db *sqlite3.Conn) {
+	sqlite3.CreateModule(db, "array", array{})
+}
+
+type array struct{}
+
+func (array) Connect(c *sqlite3.Conn, arg ...string) (_ array, err error) {
+	err = c.DeclareVtab(`CREATE TABLE x(value, array HIDDEN)`)
+	return
+}
+
+func (array) Disconnect() error {
+	return nil
+}
+
+func (array) BestIndex(idx *sqlite3.IndexInfo) error {
+	for i, cst := range idx.Constraint {
+		if cst.Column == 1 && cst.Op == sqlite3.INDEX_CONSTRAINT_EQ && cst.Usable {
+			idx.ConstraintUsage[i] = sqlite3.IndexConstraintUsage{
+				Omit:      true,
+				ArgvIndex: 1,
+			}
+			idx.EstimatedCost = 1
+			idx.EstimatedRows = 100
+			return nil
+		}
+	}
+	return sqlite3.CONSTRAINT
+}
+
+func (array) Open() (sqlite3.VTabCursor, error) {
+	return &cursor{}, nil
+}
+
+type cursor struct {
+	array reflect.Value
+	rowID int
+}
+
+func (c *cursor) EOF() bool {
+	return c.rowID >= c.array.Len()
+}
+
+func (c *cursor) Next() error {
+	c.rowID++
+	return nil
+}
+
+func (c *cursor) RowID() (int64, error) {
+	return int64(c.rowID), nil
+}
+
+func (c *cursor) Column(ctx *sqlite3.Context, n int) error {
+	if n != 0 {
+		return nil
+	}
+
+	v := c.array.Index(c.rowID)
+	k := v.Kind()
+
+	if k == reflect.Interface {
+		if v.IsNil() {
+			ctx.ResultNull()
+			return nil
+		}
+		v = v.Elem()
+		k = v.Kind()
+	}
+
+	switch {
+	case v.CanInt():
+		ctx.ResultInt64(v.Int())
+
+	case v.CanUint():
+		i64 := int64(v.Uint())
+		if i64 < 0 {
+			return fmt.Errorf("array: integer element overflow:%.0w %d", sqlite3.MISMATCH, v.Uint())
+		}
+		ctx.ResultInt64(i64)
+
+	case v.CanFloat():
+		ctx.ResultFloat(v.Float())
+
+	case k == reflect.Bool:
+		ctx.ResultBool(v.Bool())
+
+	case k == reflect.String:
+		ctx.ResultText(v.String())
+
+	case (k == reflect.Slice || k == reflect.Array) &&
+		v.Type().Elem().Kind() == reflect.Uint8:
+		ctx.ResultBlob(v.Bytes())
+
+	default:
+		return fmt.Errorf("array: unsupported element:%.0w %v", sqlite3.MISMATCH, v.Type())
+	}
+	return nil
+}
+
+func (c *cursor) Filter(idxNum int, idxStr string, arg ...sqlite3.Value) error {
+	array := reflect.ValueOf(arg[0].Pointer())
+	array, err := sliceable(array)
+	if err != nil {
+		return err
+	}
+
+	c.array = array
+	c.rowID = 0
+	return nil
+}
+
+func sliceable(v reflect.Value) (_ reflect.Value, err error) {
+	if v.Kind() == reflect.Slice {
+		return v, nil
+	}
+	if v.Kind() == reflect.Array {
+		return v, nil
+	}
+	if v.Kind() == reflect.Pointer {
+		if v := v.Elem(); v.Kind() == reflect.Array {
+			return v, nil
+		}
+	}
+	return v, fmt.Errorf("array: unsupported argument:%.0w %v", sqlite3.MISMATCH, v.Type())
+}

ext/array/array_test.go

@@ -0,0 +1,49 @@
+package array_test
+
+import (
+	"fmt"
+	"log"
+
+	"github.com/ncruces/go-sqlite3"
+	"github.com/ncruces/go-sqlite3/driver"
+	_ "github.com/ncruces/go-sqlite3/embed"
+	"github.com/ncruces/go-sqlite3/ext/array"
+)
+
+func Example() {
+	db, err := driver.Open(":memory:", func(c *sqlite3.Conn) error {
+		array.Register(c)
+		return nil
+	})
+	if err != nil {
+		log.Fatal(err)
+	}
+	defer db.Close()
+
+	rows, err := db.Query(`
+		SELECT name
+		FROM pragma_function_list
+		WHERE name like 'geopoly%' AND narg IN array(?)`,
+		sqlite3.Pointer([]int{2, 3, 4}))
+	if err != nil {
+		log.Fatal(err)
+	}
+	defer rows.Close()
+
+	for rows.Next() {
+		var name string
+		err := rows.Scan(&name)
+		if err != nil {
+			log.Fatal(err)
+		}
+		fmt.Printf("%s\n", name)
+	}
+	if err := rows.Err(); err != nil {
+		log.Fatal(err)
+	}
+	// Unordered output:
+	// geopoly_regular
+	// geopoly_overlap
+	// geopoly_contains_point
+	// geopoly_within
+}