Pivot virtual table.

ext/array/array.go

@@ -119,7 +119,7 @@ func (c *cursor) Filter(idxNum int, idxStr string, arg ...sqlite3.Value) error {
 	return nil
 }
 
-func indexable(v reflect.Value) (_ reflect.Value, err error) {
+func indexable(v reflect.Value) (reflect.Value, error) {
 	if v.Kind() == reflect.Slice {
 		return v, nil
 	}

ext/csv/schema.go

@@ -8,9 +8,9 @@ import (
 )
 
 func getSchema(header bool, columns int, row []string) string {
-	var sep = ""
+	var sep string
 	var str strings.Builder
-	str.WriteString(`CREATE TABLE x(`)
+	str.WriteString("CREATE TABLE x(")
 
 	if 0 <= columns && columns < len(row) {
 		row = row[:columns]
@@ -20,7 +20,7 @@ func getSchema(header bool, columns int, row []string) string {
 		if header && f != "" {
 			str.WriteString(sqlite3.QuoteIdentifier(f))
 		} else {
-			str.WriteByte('c')
+			str.WriteString("c")
 			str.WriteString(strconv.Itoa(i + 1))
 		}
 		str.WriteString(" TEXT")
@@ -28,7 +28,7 @@ func getSchema(header bool, columns int, row []string) string {
 	}
 	for i := len(row); i < columns; i++ {
 		str.WriteString(sep)
-		str.WriteByte('c')
+		str.WriteString("c")
 		str.WriteString(strconv.Itoa(i + 1))
 		str.WriteString(" TEXT")
 		sep = ","

ext/pivot/pivot.go

@@ -0,0 +1,267 @@
+// Package pivot implements a pivot virtual table.
+//
+// https://github.com/jakethaw/pivot_vtab
+package pivot
+
+import (
+	"errors"
+	"fmt"
+	"strings"
+
+	"github.com/ncruces/go-sqlite3"
+)
+
+// Register registers the pivot virtual table.
+func Register(db *sqlite3.Conn) {
+	sqlite3.CreateModule(db, "pivot", declare, declare)
+}
+
+type table struct {
+	db   *sqlite3.Conn
+	scan string
+	cell string
+	keys []string
+	cols []*sqlite3.Value
+}
+
+func declare(db *sqlite3.Conn, _, _, _ string, arg ...string) (_ *table, err error) {
+	if len(arg) != 3 {
+		return nil, fmt.Errorf("pivot: wrong number of arguments")
+	}
+
+	table := &table{db: db}
+	defer func() {
+		if err != nil {
+			table.Close()
+		}
+	}()
+
+	var sep string
+	var create strings.Builder
+	create.WriteString("CREATE TABLE x(")
+
+	// Row key query.
+	table.scan = "SELECT * FROM\n" + arg[0]
+	stmt, _, err := db.Prepare(table.scan)
+	if err != nil {
+		return nil, err
+	}
+	defer stmt.Close()
+
+	table.keys = make([]string, stmt.ColumnCount())
+	for i := range table.keys {
+		name := sqlite3.QuoteIdentifier(stmt.ColumnName(i))
+		table.keys[i] = name
+		create.WriteString(sep)
+		create.WriteString(name)
+		sep = ","
+	}
+	stmt.Close()
+
+	// Column definition query.
+	stmt, _, err = db.Prepare("SELECT * FROM\n" + arg[1])
+	if err != nil {
+		return nil, err
+	}
+
+	if stmt.ColumnCount() != 2 {
+		return nil, fmt.Errorf("pivot: column definition query expects 2 result columns")
+	}
+	for stmt.Step() {
+		name := sqlite3.QuoteIdentifier(stmt.ColumnText(1))
+		table.cols = append(table.cols, stmt.ColumnValue(0).Dup())
+		create.WriteString(",")
+		create.WriteString(name)
+	}
+	stmt.Close()
+
+	// Pivot cell query.
+	table.cell = "SELECT * FROM\n" + arg[2]
+	stmt, _, err = db.Prepare(table.cell)
+	if err != nil {
+		return nil, err
+	}
+
+	if stmt.ColumnCount() != 1 {
+		return nil, fmt.Errorf("pivot: cell query expects 1 result columns")
+	}
+	if stmt.BindCount() != len(table.keys)+1 {
+		return nil, fmt.Errorf("pivot: cell query expects %d bound parameters", len(table.keys)+1)
+	}
+
+	create.WriteByte(')')
+	err = db.DeclareVtab(create.String())
+	if err != nil {
+		return nil, err
+	}
+	return table, nil
+}
+
+func (t *table) Close() error {
+	for i := range t.cols {
+		t.cols[i].Close()
+	}
+	return nil
+}
+
+func (t *table) BestIndex(idx *sqlite3.IndexInfo) error {
+	var idxStr strings.Builder
+	idxStr.WriteString(t.scan)
+
+	argvIndex := 1
+	sep := " WHERE "
+	for i, cst := range idx.Constraint {
+		if !cst.Usable || !(0 <= cst.Column && cst.Column < len(t.keys)) {
+			continue
+		}
+
+		var op string
+		switch cst.Op {
+		case sqlite3.INDEX_CONSTRAINT_EQ:
+			op = "="
+		case sqlite3.INDEX_CONSTRAINT_LT:
+			op = "<"
+		case sqlite3.INDEX_CONSTRAINT_GT:
+			op = ">"
+		case sqlite3.INDEX_CONSTRAINT_LE:
+			op = "<="
+		case sqlite3.INDEX_CONSTRAINT_GE:
+			op = ">="
+		case sqlite3.INDEX_CONSTRAINT_NE:
+			op = "<>"
+		case sqlite3.INDEX_CONSTRAINT_MATCH:
+			op = "MATCH"
+		case sqlite3.INDEX_CONSTRAINT_LIKE:
+			op = "LIKE"
+		case sqlite3.INDEX_CONSTRAINT_GLOB:
+			op = "GLOB"
+		case sqlite3.INDEX_CONSTRAINT_REGEXP:
+			op = "REGEXP"
+		case sqlite3.INDEX_CONSTRAINT_IS, sqlite3.INDEX_CONSTRAINT_ISNULL:
+			op = "IS"
+		case sqlite3.INDEX_CONSTRAINT_ISNOT, sqlite3.INDEX_CONSTRAINT_ISNOTNULL:
+			op = "IS NOT"
+		default:
+			continue
+		}
+
+		idxStr.WriteString(sep)
+		idxStr.WriteString(t.keys[cst.Column])
+		idxStr.WriteString(" ")
+		idxStr.WriteString(op)
+		idxStr.WriteString(" ?")
+
+		idx.ConstraintUsage[i] = sqlite3.IndexConstraintUsage{
+			ArgvIndex: argvIndex,
+			Omit:      true,
+		}
+		sep = " AND "
+		argvIndex++
+	}
+
+	sep = " ORDER BY "
+	idx.OrderByConsumed = true
+	for _, ord := range idx.OrderBy {
+		if !(0 <= ord.Column && ord.Column < len(t.keys)) {
+			idx.OrderByConsumed = false
+			continue
+		}
+		idxStr.WriteString(sep)
+		idxStr.WriteString(t.keys[ord.Column])
+		if ord.Desc {
+			idxStr.WriteString(" DESC")
+		}
+		sep = ","
+	}
+
+	idx.EstimatedCost = 1e9 / float64(argvIndex)
+	idx.IdxStr = idxStr.String()
+	return nil
+}
+
+func (t *table) Open() (sqlite3.VTabCursor, error) {
+	return &cursor{table: t}, nil
+}
+
+func (t *table) Rename(new string) error {
+	return nil
+}
+
+type cursor struct {
+	table *table
+	scan  *sqlite3.Stmt
+	cell  *sqlite3.Stmt
+	rowID int64
+}
+
+func (c *cursor) Close() error {
+	return errors.Join(c.scan.Close(), c.cell.Close())
+}
+
+func (c *cursor) Filter(idxNum int, idxStr string, arg ...sqlite3.Value) error {
+	err := c.scan.Close()
+	if err != nil {
+		return err
+	}
+
+	c.scan, _, err = c.table.db.Prepare(idxStr)
+	if err != nil {
+		return err
+	}
+	for i, arg := range arg {
+		err := c.scan.BindValue(i+1, arg)
+		if err != nil {
+			return err
+		}
+	}
+
+	if c.cell == nil {
+		c.cell, _, err = c.table.db.Prepare(c.table.cell)
+		if err != nil {
+			return err
+		}
+	}
+
+	c.rowID = 0
+	return c.Next()
+}
+
+func (c *cursor) Next() error {
+	if c.scan.Step() {
+		count := c.scan.ColumnCount()
+		for i := 0; i < count; i++ {
+			err := c.cell.BindValue(i+1, c.scan.ColumnValue(i))
+			if err != nil {
+				return err
+			}
+		}
+		c.rowID++
+	}
+	return c.scan.Err()
+}
+
+func (c *cursor) EOF() bool {
+	return !c.scan.Busy()
+}
+
+func (c *cursor) RowID() (int64, error) {
+	return c.rowID, nil
+}
+
+func (c *cursor) Column(ctx *sqlite3.Context, col int) error {
+	count := c.scan.ColumnCount()
+	if col < count {
+		ctx.ResultValue(c.scan.ColumnValue(col))
+		return nil
+	}
+
+	err := c.cell.BindValue(count+1, *c.table.cols[col-count])
+	if err != nil {
+		return err
+	}
+
+	if c.cell.Step() {
+		ctx.ResultValue(c.cell.ColumnValue(0))
+	}
+	return c.cell.Reset()
+}

ext/pivot/pivot_test.go

@@ -0,0 +1,219 @@
+package pivot_test
+
+import (
+	"fmt"
+	"log"
+	"strings"
+	"testing"
+
+	"github.com/ncruces/go-sqlite3"
+	_ "github.com/ncruces/go-sqlite3/embed"
+	"github.com/ncruces/go-sqlite3/ext/pivot"
+)
+
+// https://antonz.org/sqlite-pivot-table/
+func Example() {
+	db, err := sqlite3.Open(":memory:")
+	if err != nil {
+		log.Fatal(err)
+	}
+	defer db.Close()
+
+	pivot.Register(db)
+
+	err = db.Exec(`
+		CREATE TABLE sales(product TEXT, year INT, income DECIMAL);
+		INSERT INTO  sales(product, year, income) VALUES
+			('alpha', 2020, 100),
+			('alpha', 2021, 120),
+			('alpha', 2022, 130),
+			('alpha', 2023, 140),
+			('beta',  2020, 10),
+			('beta',  2021, 20),
+			('beta',  2022, 40),
+			('beta',  2023, 80),
+			('gamma', 2020, 80),
+			('gamma', 2021, 75),
+			('gamma', 2022, 78),
+			('gamma', 2023, 80);
+	`)
+	if err != nil {
+		log.Fatal(err)
+	}
+
+	err = db.Exec(`
+		CREATE VIRTUAL TABLE v_sales USING pivot(
+			-- rows
+			(SELECT DISTINCT product FROM sales),
+			-- columns
+			(SELECT DISTINCT year, year FROM sales),
+			-- cells
+			(SELECT sum(income) FROM sales WHERE product = ? AND year = ?)
+		)`)
+	if err != nil {
+		log.Fatal(err)
+	}
+
+	stmt, _, err := db.Prepare(`SELECT * FROM v_sales`)
+	if err != nil {
+		log.Fatal(err)
+	}
+	defer stmt.Close()
+
+	cols := make([]string, stmt.ColumnCount())
+	for i := range cols {
+		cols[i] = stmt.ColumnName(i)
+	}
+	fmt.Println(pretty(cols))
+	for stmt.Step() {
+		for i := range cols {
+			cols[i] = stmt.ColumnText(i)
+		}
+		fmt.Println(pretty(cols))
+	}
+	if err := stmt.Reset(); err != nil {
+		log.Fatal(err)
+	}
+
+	// Output:
+	// product 2020    2021    2022    2023
+	// alpha   100     120     130     140
+	// beta    10      20      40      80
+	// gamma   80      75      78      80
+}
+
+func TestRegister(t *testing.T) {
+	t.Parallel()
+
+	db, err := sqlite3.Open(":memory:")
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer db.Close()
+
+	pivot.Register(db)
+
+	err = db.Exec(`
+		CREATE TABLE r AS
+			SELECT 1 id UNION SELECT 2 UNION SELECT 3;
+
+		CREATE TABLE c(
+			id   INTEGER PRIMARY KEY,
+			name TEXT
+		);
+		INSERT INTO c (name) VALUES
+			('a'),('b'),('c'),('d');
+
+		CREATE TABLE x(
+			r_id INT,
+			c_id INT,
+			val  TEXT
+		);
+		INSERT INTO x (r_id, c_id, val)
+			SELECT r.id, c.id, c.name || r.id
+			FROM c, r;				
+	`)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	err = db.Exec(`
+		CREATE VIRTUAL TABLE v_x USING pivot(
+			-- rows
+			(SELECT id r_id FROM r),
+			-- columns
+			(SELECT id c_id, name FROM c),
+			-- cells
+			(SELECT val FROM x WHERE r_id = ?1 AND c_id = ?2)
+		)`)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	stmt, _, err := db.Prepare(`SELECT * FROM v_x WHERE rowid <> 0 AND r_id <> 1 ORDER BY rowid, r_id DESC LIMIT 1`)
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer stmt.Close()
+
+	if stmt.Step() {
+		if got := stmt.ColumnInt(0); got != 3 {
+			t.Errorf("got %d, want 3", got)
+		}
+	}
+}
+
+func TestRegister_errors(t *testing.T) {
+	t.Parallel()
+
+	db, err := sqlite3.Open(":memory:")
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer db.Close()
+
+	pivot.Register(db)
+
+	err = db.Exec(`CREATE VIRTUAL TABLE pivot USING pivot()`)
+	if err == nil {
+		t.Fatal("want error")
+	} else {
+		t.Log(err)
+	}
+
+	err = db.Exec(`CREATE VIRTUAL TABLE split_date USING pivot(SELECT 1, SELECT 2, SELECT 3)`)
+	if err == nil {
+		t.Fatal("want error")
+	} else {
+		t.Log(err)
+	}
+
+	err = db.Exec(`CREATE VIRTUAL TABLE split_date USING pivot((SELECT 1), SELECT 2, SELECT 3)`)
+	if err == nil {
+		t.Fatal("want error")
+	} else {
+		t.Log(err)
+	}
+
+	err = db.Exec(`CREATE VIRTUAL TABLE split_date USING pivot((SELECT 1), (SELECT 2), SELECT 3)`)
+	if err == nil {
+		t.Fatal("want error")
+	} else {
+		t.Log(err)
+	}
+
+	err = db.Exec(`CREATE VIRTUAL TABLE split_date USING pivot((SELECT 1), (SELECT 1, 2), SELECT 3)`)
+	if err == nil {
+		t.Fatal("want error")
+	} else {
+		t.Log(err)
+	}
+
+	err = db.Exec(`CREATE VIRTUAL TABLE split_date USING pivot((SELECT 1), (SELECT 1, 2), (SELECT 3, 4))`)
+	if err == nil {
+		t.Fatal("want error")
+	} else {
+		t.Log(err)
+	}
+
+	err = db.Exec(`CREATE VIRTUAL TABLE split_date USING pivot((SELECT 1), (SELECT 1, 2), (SELECT 3))`)
+	if err == nil {
+		t.Fatal("want error")
+	} else {
+		t.Log(err)
+	}
+}
+
+func pretty(cols []string) string {
+	var buf strings.Builder
+	for i, s := range cols {
+		if i != 0 {
+			buf.WriteByte(' ')
+		}
+		for buf.Len()%8 != 0 {
+			buf.WriteByte(' ')
+		}
+		buf.WriteString(s)
+	}
+	return buf.String()
+}

ext/statement/stmt.go

@@ -15,55 +15,6 @@ import (
 
 // Register registers the statement virtual table.
 func Register(db *sqlite3.Conn) {
-	declare := func(db *sqlite3.Conn, _, _, _ string, arg ...string) (*table, error) {
-		if len(arg) != 1 {
-			return nil, fmt.Errorf("statement: wrong number of arguments")
-		}
-
-		sql := "SELECT * FROM\n" + arg[0]
-
-		stmt, _, err := db.Prepare(sql)
-		if err != nil {
-			return nil, err
-		}
-
-		var sep = ""
-		var str strings.Builder
-		str.WriteString(`CREATE TABLE x(`)
-		outputs := stmt.ColumnCount()
-		for i := 0; i < outputs; i++ {
-			name := sqlite3.QuoteIdentifier(stmt.ColumnName(i))
-			str.WriteString(sep)
-			str.WriteString(name)
-			str.WriteByte(' ')
-			str.WriteString(stmt.ColumnDeclType(i))
-			sep = ","
-		}
-		inputs := stmt.BindCount()
-		for i := 1; i <= inputs; i++ {
-			str.WriteString(sep)
-			name := stmt.BindName(i)
-			if name == "" {
-				str.WriteString("[")
-				str.WriteString(strconv.Itoa(i))
-				str.WriteString("] HIDDEN")
-			} else {
-				str.WriteString(sqlite3.QuoteIdentifier(name[1:]))
-				str.WriteString(" HIDDEN")
-			}
-			sep = ","
-		}
-		str.WriteByte(')')
-
-		err = db.DeclareVtab(str.String())
-		if err != nil {
-			stmt.Close()
-			return nil, err
-		}
-
-		return &table{sql: sql, stmt: stmt}, nil
-	}
-
 	sqlite3.CreateModule(db, "statement", declare, declare)
 }
 
@@ -73,6 +24,55 @@ type table struct {
 	inuse bool
 }
 
+func declare(db *sqlite3.Conn, _, _, _ string, arg ...string) (*table, error) {
+	if len(arg) != 1 {
+		return nil, fmt.Errorf("statement: wrong number of arguments")
+	}
+
+	sql := "SELECT * FROM\n" + arg[0]
+
+	stmt, _, err := db.Prepare(sql)
+	if err != nil {
+		return nil, err
+	}
+
+	var sep string
+	var str strings.Builder
+	str.WriteString("CREATE TABLE x(")
+	outputs := stmt.ColumnCount()
+	for i := 0; i < outputs; i++ {
+		name := sqlite3.QuoteIdentifier(stmt.ColumnName(i))
+		str.WriteString(sep)
+		str.WriteString(name)
+		str.WriteString(" ")
+		str.WriteString(stmt.ColumnDeclType(i))
+		sep = ","
+	}
+	inputs := stmt.BindCount()
+	for i := 1; i <= inputs; i++ {
+		str.WriteString(sep)
+		name := stmt.BindName(i)
+		if name == "" {
+			str.WriteString("[")
+			str.WriteString(strconv.Itoa(i))
+			str.WriteString("] HIDDEN")
+		} else {
+			str.WriteString(sqlite3.QuoteIdentifier(name[1:]))
+			str.WriteString(" HIDDEN")
+		}
+		sep = ","
+	}
+	str.WriteByte(')')
+
+	err = db.DeclareVtab(str.String())
+	if err != nil {
+		stmt.Close()
+		return nil, err
+	}
+
+	return &table{sql: sql, stmt: stmt}, nil
+}
+
 func (t *table) Close() error {
 	return t.stmt.Close()
 }
@@ -120,11 +120,12 @@ func (t *table) BestIndex(idx *sqlite3.IndexInfo) error {
 	return nil
 }
 
-func (t *table) Open() (_ sqlite3.VTabCursor, err error) {
+func (t *table) Open() (sqlite3.VTabCursor, error) {
 	stmt := t.stmt
 	if !t.inuse {
 		t.inuse = true
 	} else {
+		var err error
 		stmt, _, err = t.stmt.Conn().Prepare(t.sql)
 		if err != nil {
 			return nil, err
@@ -186,7 +187,6 @@ func (c *cursor) Filter(idxNum int, idxStr string, arg ...sqlite3.Value) error {
 func (c *cursor) Next() error {
 	if c.stmt.Step() {
 		c.rowID++
-		return nil
 	}
 	return c.stmt.Err()
 }

ext/statement/stmt_test.go

@@ -95,7 +95,6 @@ func TestRegister(t *testing.T) {
 			t.Errorf("hypot(%d, %d) = %d", x, y, hypot)
 		}
 	}
-
 }
 
 func TestRegister_errors(t *testing.T) {