feat: implement GenericLoader for batch processing and utility functions

cmd/go_migrate/connect.go

@@ -1,77 +0,0 @@
-package main
-
-import (
-	"context"
-	"database/sql"
-	"errors"
-	"fmt"
-	"sync"
-	"time"
-
-	"git.ksdemosapps.com/kylesoda/go-migrate/internal/app/config"
-	"github.com/jackc/pgx/v5/pgxpool"
-	_ "github.com/microsoft/go-mssqldb"
-	log "github.com/sirupsen/logrus"
-)
-
-func connectToSqlServer() (*sql.DB, error) {
-	db, err := sql.Open("sqlserver", config.App.SourceDbUrl)
-	if err != nil {
-		return nil, fmt.Errorf("Unable to connect to sqlserver: %w", err)
-	}
-
-	ctx, cancel := context.WithTimeout(context.Background(), 20*time.Second)
-	defer cancel()
-
-	if err := db.PingContext(ctx); err != nil {
-		return nil, fmt.Errorf("Unable to ping sqlserver: %w", err)
-	}
-
-	return db, nil
-}
-
-func connectToPostgres() (*pgxpool.Pool, error) {
-	ctx, cancel := context.WithTimeout(context.Background(), 20*time.Second)
-	defer cancel()
-
-	pool, err := pgxpool.New(ctx, config.App.TargetDbUrl)
-	if err != nil {
-		return nil, fmt.Errorf("Unable to connect to postgres: %w", err)
-	}
-
-	if err := pool.Ping(ctx); err != nil {
-		pool.Close()
-		return nil, fmt.Errorf("Unable to ping postgres: %w", err)
-	}
-
-	return pool, nil
-}
-
-func connectToDatabases() (*sql.DB, *pgxpool.Pool, error) {
-	var sourceDbErr, targetDbErr error
-	var sourceDb *sql.DB
-	var targetDb *pgxpool.Pool
-	var wg sync.WaitGroup
-
-	wg.Go(func() {
-		sourceDb, sourceDbErr = connectToSqlServer()
-		if sourceDbErr != nil {
-			log.Error("Unable to connect to source db: ", sourceDbErr)
-		}
-	})
-
-	wg.Go(func() {
-		targetDb, targetDbErr = connectToPostgres()
-		if targetDbErr != nil {
-			log.Error("Unable to connect to target db: ", targetDbErr)
-		}
-	})
-
-	wg.Wait()
-
-	if sourceDbErr != nil || targetDbErr != nil {
-		return nil, nil, errors.New("Unable to connect to databases")
-	}
-
-	return sourceDb, targetDb, nil
-}

cmd/go_migrate/main.go

@@ -11,6 +11,7 @@ import (
 	"git.ksdemosapps.com/kylesoda/go-migrate/internal/app/etl/loaders"
 	"git.ksdemosapps.com/kylesoda/go-migrate/internal/app/etl/table_analyzers"
 	"git.ksdemosapps.com/kylesoda/go-migrate/internal/app/etl/transformers"
+	"git.ksdemosapps.com/kylesoda/go-migrate/internal/app/models"
 	log "github.com/sirupsen/logrus"
 	"golang.org/x/sync/errgroup"
 )
@@ -95,10 +96,10 @@ func processMigrationJobs(
 	targetDb dbwrapper.DbWrapper,
 	jobs []config.Job,
 	maxParallelWorkers int,
-) []JobResult {
+) []models.JobResult {
 	if len(jobs) == 0 {
 		log.Info("No migration jobs configured")
-		return []JobResult{}
+		return []models.JobResult{}
 	}
 
 	if maxParallelWorkers <= 0 {
@@ -111,7 +112,7 @@ func processMigrationJobs(
 
 	log.Infof("Starting migration with %d parallel worker(s)", maxParallelWorkers)
 
-	chJobResults := make(chan JobResult, len(jobs))
+	chJobResults := make(chan models.JobResult, len(jobs))
 	chJobs := make(chan config.Job, len(jobs))
 	var wgJobs sync.WaitGroup
 
@@ -119,7 +120,7 @@ func processMigrationJobs(
 	targetTableAnalyzer := table_analyzers.NewPostgresTableAnalyzer(targetDb)
 	extractor := extractors.NewMssqlExtractor(sourceDb)
 	transformer := transformers.NewMssqlTransformer()
-	loader := loaders.NewPostgresLoader(targetDb)
+	loader := loaders.NewGenericLoader(targetDb)
 
 	for i := range maxParallelWorkers {
 		wgJobs.Go(func() {
@@ -151,7 +152,7 @@ func processMigrationJobs(
 		close(chJobResults)
 	}()
 
-	var finalResults []JobResult
+	var finalResults []models.JobResult
 	for res := range chJobResults {
 		finalResults = append(finalResults, res)
 	}

cmd/go_migrate/metrics.go

@@ -1,13 +0,0 @@
-package main
-
-import "time"
-
-type JobResult struct {
-	JobName    string
-	StartTime  time.Time
-	Duration   time.Duration
-	RowsRead   int64
-	RowsLoaded int64
-	RowsFailed int64
-	Error      error
-}

cmd/go_migrate/process.go

@@ -26,11 +26,11 @@ func processMigrationJob(
 	transformer etl.Transformer,
 	loader etl.Loader,
 	job config.Job,
-) JobResult {
+) models.JobResult {
 	localCtx, cancel := context.WithCancel(ctx)
 	defer cancel()
 
-	result := JobResult{
+	result := models.JobResult{
 		JobName:   job.Name,
 		StartTime: time.Now(),
 	}

internal/app/etl/loaders/main.go

@@ -15,31 +15,21 @@ import (
 	"github.com/jackc/pgx/v5/pgconn"
 )
 
-type PostgresLoader struct {
+type GenericLoader struct {
 	db dbwrapper.DbWrapper
 }
 
-func NewPostgresLoader(db dbwrapper.DbWrapper) etl.Loader {
+func NewGenericLoader(db dbwrapper.DbWrapper) etl.Loader {
-	return &PostgresLoader{db: db}
+	return &GenericLoader{db: db}
 }
 
-func mapSlice[T any, V any](input []T, mapper func(T) V) []V {
+func (gl *GenericLoader) ProcessBatch(
-	result := make([]V, len(input))
-
-	for i, v := range input {
-		result[i] = mapper(v)
-	}
-
-	return result
-}
-
-func (postgresLd *PostgresLoader) ProcessBatch(
 	ctx context.Context,
 	tableInfo config.TargetTableInfo,
 	colNames []string,
 	batch models.Batch,
 ) (int, error) {
-	_, err := postgresLd.db.SaveMassive(
+	_, err := gl.db.SaveMassive(
 		ctx,
 		tableInfo.Schema,
 		tableInfo.Table,
@@ -65,7 +55,7 @@ func (postgresLd *PostgresLoader) ProcessBatch(
 	return len(batch.Rows), nil
 }
 
-func (postgresLd *PostgresLoader) Exec(
+func (gl *GenericLoader) Exec(
 	ctx context.Context,
 	tableInfo config.TargetTableInfo,
 	columns []models.ColumnType,
@@ -92,7 +82,7 @@ func (postgresLd *PostgresLoader) Exec(
 				return
 			}
 
-			processedRows, err := postgresLd.ProcessBatch(ctx, tableInfo, colNames, batch)
+			processedRows, err := gl.ProcessBatch(ctx, tableInfo, colNames, batch)
 
 			if err != nil {
 				var ldError *custom_errors.LoaderError

internal/app/etl/loaders/types.go

@@ -1 +0,0 @@
-package loaders

internal/app/etl/loaders/utils.go

@@ -0,0 +1,11 @@
+package loaders
+
+func mapSlice[T any, V any](input []T, mapper func(T) V) []V {
+	result := make([]V, len(input))
+
+	for i, v := range input {
+		result[i] = mapper(v)
+	}
+
+	return result
+}

internal/app/models/main.go

@@ -1,6 +1,10 @@
 package models
 
-import "github.com/google/uuid"
+import (
+	"time"
+
+	"github.com/google/uuid"
+)
 
 type UnknownRowValues = []any
 
@@ -25,3 +29,13 @@ type Partition struct {
 	HasRange     bool
 	RetryCounter int
 }
+
+type JobResult struct {
+	JobName    string
+	StartTime  time.Time
+	Duration   time.Duration
+	RowsRead   int64
+	RowsLoaded int64
+	RowsFailed int64
+	Error      error
+}