Source File
	binaryscalarexpr.go

Belonging Package
	github.com/polarsignals/frostdb/query/physicalplan

package physicalplan

import (
	"bytes"
	"context"
	"errors"
	"fmt"
	"unsafe"

	"github.com/apache/arrow-go/v18/arrow"
	"github.com/apache/arrow-go/v18/arrow/array"
	"github.com/apache/arrow-go/v18/arrow/compute"
	"github.com/apache/arrow-go/v18/arrow/scalar"

	"github.com/polarsignals/frostdb/query/logicalplan"
)

type ArrayRef struct {
	ColumnName string
}

func (a *ArrayRef) ArrowArray(r arrow.Record) (arrow.Array, bool, error) {
	fields := r.Schema().FieldIndices(a.ColumnName)
	if len(fields) != 1 {
		return nil, false, nil
	}

	return r.Column(fields[0]), true, nil
}

func (a *ArrayRef) String() string {
	return a.ColumnName
}

type BinaryScalarExpr struct {
	Left  *ArrayRef
	Op    logicalplan.Op
	Right scalar.Scalar
}

func (e BinaryScalarExpr) Eval(r arrow.Record) (*Bitmap, error) {
	leftData, exists, err := e.Left.ArrowArray(r)
	if err != nil {
		return nil, err
	}

	if !exists {
		res := NewBitmap()
		switch e.Op {
		case logicalplan.OpEq:
			if e.Right.IsValid() { // missing column; looking for == non-nil
				switch t := e.Right.(type) {
				case *scalar.Binary:
					if t.String() != "" { // treat empty string equivalent to nil
						return res, nil
					}
				case *scalar.String:
					if t.String() != "" { // treat empty string equivalent to nil
						return res, nil
					}
				}
			}
		case logicalplan.OpNotEq: // missing column; looking for != nil
			if !e.Right.IsValid() {
				return res, nil
			}
		case logicalplan.OpLt, logicalplan.OpLtEq, logicalplan.OpGt, logicalplan.OpGtEq:
			return res, nil
		}

		res.AddRange(0, uint64(r.NumRows()))
		return res, nil
	}

	return BinaryScalarOperation(leftData, e.Right, e.Op)
}

func (e BinaryScalarExpr) String() string {
	return e.Left.String() + " " + e.Op.String() + " " + e.Right.String()
}

var ErrUnsupportedBinaryOperation = errors.New("unsupported binary operation")

func BinaryScalarOperation(left arrow.Array, right scalar.Scalar, operator logicalplan.Op) (*Bitmap, error) {
	switch operator {
	case logicalplan.OpContains, logicalplan.OpNotContains:
		switch arr := left.(type) {
		case *array.Binary, *array.String:
			return ArrayScalarContains(left, right, operator == logicalplan.OpNotContains)
		case *array.Dictionary:
			return DictionaryArrayScalarContains(arr, right, operator == logicalplan.OpNotContains)
		default:
			panic("unsupported array type " + fmt.Sprintf("%T", arr))
		}
	}

	// TODO: Figure out dictionary arrays and lists with compute next
	leftType := left.DataType()
	switch arr := left.(type) {
	case *array.Dictionary:
		switch operator {
		case logicalplan.OpEq:
			return DictionaryArrayScalarEqual(arr, right)
		case logicalplan.OpNotEq:
			return DictionaryArrayScalarNotEqual(arr, right)
		default:
			return nil, fmt.Errorf("unsupported operator: %v", operator)
		}
	}

	switch leftType.(type) {
	case *arrow.ListType:
		panic("TODO: list comparisons unimplemented")
	}

	return ArrayScalarCompute(operator.ArrowString(), left, right)
}

func ArrayScalarCompute(funcName string, left arrow.Array, right scalar.Scalar) (*Bitmap, error) {
	leftData := compute.NewDatum(left)
	defer leftData.Release()
	rightData := compute.NewDatum(right)
	defer rightData.Release()
	equalsResult, err := compute.CallFunction(context.TODO(), funcName, nil, leftData, rightData)
	if err != nil {
		if errors.Unwrap(err).Error() == "not implemented" {
			return nil, ErrUnsupportedBinaryOperation
		}
		return nil, fmt.Errorf("error calling equal function: %w", err)
	}
	defer equalsResult.Release()
	equalsDatum, ok := equalsResult.(*compute.ArrayDatum)
	if !ok {
		return nil, fmt.Errorf("expected *compute.ArrayDatum, got %T", equalsResult)
	}
	equalsArray, ok := equalsDatum.MakeArray().(*array.Boolean)
	if !ok {
		return nil, fmt.Errorf("expected *array.Boolean, got %T", equalsDatum.MakeArray())
	}
	defer equalsArray.Release()

	res := NewBitmap()
	for i := 0; i < equalsArray.Len(); i++ {
		if equalsArray.IsNull(i) {
			continue
		}
		if equalsArray.Value(i) {
			res.AddInt(i)
		}
	}
	return res, nil
}

func DictionaryArrayScalarNotEqual(left *array.Dictionary, right scalar.Scalar) (*Bitmap, error) {
	res := NewBitmap()
	var data []byte
	switch r := right.(type) {
	case *scalar.Binary:
		data = r.Data()
	case *scalar.String:
		data = r.Data()
	}

	// This is a special case for where the left side should not equal NULL
	if right == scalar.ScalarNull {
		for i := 0; i < left.Len(); i++ {
			if !left.IsNull(i) {
				res.Add(uint32(i))
			}
		}
		return res, nil
	}

	for i := 0; i < left.Len(); i++ {
		if left.IsNull(i) {
			continue
		}

		switch dict := left.Dictionary().(type) {
		case *array.Binary:
			if !bytes.Equal(dict.Value(left.GetValueIndex(i)), data) {
				res.Add(uint32(i))
			}
		case *array.String:
			if dict.Value(left.GetValueIndex(i)) != string(data) {
				res.Add(uint32(i))
			}
		}
	}

	return res, nil
}

func DictionaryArrayScalarEqual(left *array.Dictionary, right scalar.Scalar) (*Bitmap, error) {
	res := NewBitmap()
	var data []byte
	switch r := right.(type) {
	case *scalar.Binary:
		data = r.Data()
	case *scalar.String:
		data = r.Data()
	}

	// This is a special case for where the left side should equal NULL
	if right == scalar.ScalarNull {
		for i := 0; i < left.Len(); i++ {
			if left.IsNull(i) {
				res.Add(uint32(i))
			}
		}
		return res, nil
	}

	for i := 0; i < left.Len(); i++ {
		if left.IsNull(i) {
			continue
		}

		switch dict := left.Dictionary().(type) {
		case *array.Binary:
			if bytes.Equal(dict.Value(left.GetValueIndex(i)), data) {
				res.Add(uint32(i))
			}
		case *array.String:
			if dict.Value(left.GetValueIndex(i)) == string(data) {
				res.Add(uint32(i))
			}
		}
	}

	return res, nil
}

func ArrayScalarContains(arr arrow.Array, right scalar.Scalar, not bool) (*Bitmap, error) {
	var r []byte
	switch s := right.(type) {
	case *scalar.Binary:
		r = s.Data()
	case *scalar.String:
		r = s.Data()
	}

	res := NewBitmap()
	switch a := arr.(type) {
	case *array.Binary:
		for i := 0; i < a.Len(); i++ {
			if a.IsNull(i) {
				continue
			}
			contains := bytes.Contains(a.Value(i), r)
			if contains && !not || !contains && not {
				res.Add(uint32(i))
			}
		}
		return res, nil
	case *array.String:
		for i := 0; i < a.Len(); i++ {
			if a.IsNull(i) {
				continue
			}
			contains := bytes.Contains(unsafeStringToBytes(a.Value(i)), r)
			if contains && !not || !contains && not {
				res.Add(uint32(i))
			}
		}
		return res, nil
	}
	return nil, fmt.Errorf("contains not implemented for %T", arr)
}

func DictionaryArrayScalarContains(left *array.Dictionary, right scalar.Scalar, not bool) (*Bitmap, error) {
	res := NewBitmap()
	var data []byte
	switch r := right.(type) {
	case *scalar.Binary:
		data = r.Data()
	case *scalar.String:
		data = r.Data()
	}

	// This is a special case for where the left side should not equal NULL
	if right == scalar.ScalarNull {
		for i := 0; i < left.Len(); i++ {
			if !left.IsNull(i) {
				res.Add(uint32(i))
			}
		}
		return res, nil
	}

	for i := 0; i < left.Len(); i++ {
		if left.IsNull(i) {
			continue
		}

		switch dict := left.Dictionary().(type) {
		case *array.Binary:
			contains := bytes.Contains(dict.Value(left.GetValueIndex(i)), data)
			if contains && !not || !contains && not {
				res.Add(uint32(i))
			}
		case *array.String:
			contains := bytes.Contains(unsafeStringToBytes(dict.Value(left.GetValueIndex(i))), data)
			if contains && !not || !contains && not {
				res.Add(uint32(i))
			}
		}
	}

	return res, nil
}

func unsafeStringToBytes(s string) []byte {
	return unsafe.Slice(unsafe.StringData(s), len(s))
}

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