feat: implement MSSQL extractor, transformer, and Postgres loader for enhanced data migration

internal/app/etl/transformers/mssql.go

@@ -0,0 +1,150 @@
+package transformers
+
+import (
+	"context"
+	"errors"
+	"sync"
+	"time"
+
+	"git.ksdemosapps.com/kylesoda/go-migrate/internal/app/custom_errors"
+	"git.ksdemosapps.com/kylesoda/go-migrate/internal/app/etl"
+	"git.ksdemosapps.com/kylesoda/go-migrate/internal/app/models"
+)
+
+type MssqlTransformer struct{}
+
+func NewMssqlTransformer() etl.Transformer {
+	return &MssqlTransformer{}
+}
+
+func computeTransformationPlan(columns []models.ColumnType) []etl.ColumnTransformPlan {
+	var plan []etl.ColumnTransformPlan
+
+	for i, col := range columns {
+		switch col.SystemType() {
+		case "uniqueidentifier":
+			plan = append(plan, etl.ColumnTransformPlan{
+				Index: i,
+				Fn: func(v any) (any, error) {
+					if b, ok := v.([]byte); ok && b != nil {
+						return mssqlUuidToBigEndian(b)
+					}
+					return v, nil
+				},
+			})
+
+		case "geometry", "geography":
+			plan = append(plan, etl.ColumnTransformPlan{
+				Index: i,
+				Fn: func(v any) (any, error) {
+					if b, ok := v.([]byte); ok && b != nil {
+						return wkbToEwkbWithSrid(b, 4326)
+					}
+					return v, nil
+				},
+			})
+
+		case "datetime", "datetime2":
+			plan = append(plan, etl.ColumnTransformPlan{
+				Index: i,
+				Fn: func(v any) (any, error) {
+					if t, ok := v.(time.Time); ok {
+						return ensureUTC(t), nil
+					}
+					return v, nil
+				},
+			})
+		}
+	}
+
+	return plan
+}
+
+const processChunkCtxCheck = 4096
+
+func (mssqlTr *MssqlTransformer) ProcessChunk(
+	ctx context.Context,
+	chunk *models.Chunk,
+	transformationPlan []etl.ColumnTransformPlan,
+) error {
+	for i, rowValues := range chunk.Data {
+		if i%processChunkCtxCheck == 0 {
+			if err := ctx.Err(); err != nil {
+				return err
+			}
+		}
+
+		for _, task := range transformationPlan {
+			val := rowValues[task.Index]
+			if val == nil {
+				continue
+			}
+
+			transformed, err := task.Fn(val)
+			if err != nil {
+				return err
+			}
+			rowValues[task.Index] = transformed
+		}
+	}
+
+	return nil
+}
+
+func (mssqlTr *MssqlTransformer) Exec(
+	ctx context.Context,
+	columns []models.ColumnType,
+	chChunksIn <-chan models.Chunk,
+	chChunksOut chan<- models.Chunk,
+	chJobErrorsOut chan<- custom_errors.JobError,
+	wgActiveChunks *sync.WaitGroup,
+) {
+	transformationPlan := computeTransformationPlan(columns)
+
+	for {
+		if ctx.Err() != nil {
+			return
+		}
+
+		select {
+		case <-ctx.Done():
+			return
+
+		case chunk, ok := <-chChunksIn:
+			if !ok {
+				return
+			}
+
+			if len(transformationPlan) == 0 {
+				select {
+				case chChunksOut <- chunk:
+					wgActiveChunks.Add(1)
+					continue
+				case <-ctx.Done():
+					return
+				}
+			}
+
+			err := mssqlTr.ProcessChunk(ctx, &chunk, transformationPlan)
+			if err != nil {
+				if errors.Is(err, ctx.Err()) {
+					return
+				}
+
+				select {
+				case chJobErrorsOut <- custom_errors.JobError{ShouldCancelJob: true, Msg: "Transformation failed", Prev: err}:
+				case <-ctx.Done():
+				}
+				return
+			}
+
+			select {
+			case chChunksOut <- chunk:
+			case <-ctx.Done():
+				return
+			}
+
+			wgActiveChunks.Add(1)
+		}
+	}
+}

internal/app/etl/transformers/types.go

@@ -0,0 +1 @@
+package transformers

internal/app/etl/transformers/utils.go

@@ -0,0 +1,80 @@
+package transformers
+
+import (
+	"encoding/binary"
+	"errors"
+	"time"
+)
+
+func mssqlUuidToBigEndian(mssqlUuid []byte) ([]byte, error) {
+	if len(mssqlUuid) != 16 {
+		return nil, errors.New("Invalid uuid")
+	}
+
+	pgUuid := make([]byte, 16)
+	pgUuid[0], pgUuid[1], pgUuid[2], pgUuid[3] = mssqlUuid[3], mssqlUuid[2], mssqlUuid[1], mssqlUuid[0]
+	pgUuid[4], pgUuid[5] = mssqlUuid[5], mssqlUuid[4]
+	pgUuid[6], pgUuid[7] = mssqlUuid[7], mssqlUuid[6]
+	copy(pgUuid[8:], mssqlUuid[8:])
+
+	return pgUuid, nil
+}
+
+const sridFlag = 0x20000000
+
+func wkbToEwkbWithSrid(geometry []byte, srid int) ([]byte, error) {
+	if len(geometry) < 5 {
+		return nil, errors.New("Invalid wkb")
+	}
+
+	var byteOrder binary.ByteOrder
+	if geometry[0] == 0 {
+		byteOrder = binary.BigEndian
+	} else {
+		byteOrder = binary.LittleEndian
+	}
+
+	wkbType := byteOrder.Uint32(geometry[1:5])
+	if wkbType&sridFlag != 0 {
+		return geometry, nil
+	}
+
+	ewkbType := wkbType | sridFlag
+
+	result := make([]byte, len(geometry)+4)
+
+	result[0] = geometry[0]
+
+	byteOrder.PutUint32(result[1:5], ewkbType)
+
+	byteOrder.PutUint32(result[5:9], uint32(srid))
+
+	copy(result[9:], geometry[5:])
+
+	return result, nil
+}
+
+func ensureUTC(t time.Time) time.Time {
+	if t.Location() == time.UTC {
+		return t
+	}
+
+	return time.Date(t.Year(), t.Month(), t.Day(), t.Hour(), t.Minute(), t.Second(), t.Nanosecond(), time.UTC)
+}
+
+func ToInt64(v any) (int64, bool) {
+	switch t := v.(type) {
+	case int:
+		return int64(t), true
+	case int8:
+		return int64(t), true
+	case int16:
+		return int64(t), true
+	case int32:
+		return int64(t), true
+	case int64:
+		return int64(t), true
+	default:
+		return 0, false
+	}
+}