feat: add extractData method for retrieving data from postgresql

cmd/go_migrate/main.go

@@ -1,8 +1,15 @@
 package main
 
 import (
+	"context"
+	"errors"
+	"fmt"
 	"time"
 
+	"git.ksdemosapps.com/kylesoda/go-migrate/internal/app/config"
+	"git.ksdemosapps.com/kylesoda/go-migrate/internal/app/db"
+	"github.com/jackc/pgx/v5"
+	"github.com/jackc/pgx/v5/pgconn"
 	log "github.com/sirupsen/logrus"
 )
 
@@ -11,7 +18,100 @@ func main() {
 		FullTimestamp:   true,
 		TimestampFormat: time.StampMilli,
 	})
+	log.SetLevel(log.DebugLevel)
 
 	log.Info("Starting migration...")
+	rowValues, colNames, err := extractData()
+
+	if err != nil {
+		log.Fatal("Unexpected error when extracting data")
+	}
+
+	for index, row := range rowValues {
+		log.Debugf("Values for row %d", index+1)
+		for i, v := range row {
+			log.Debugf("%s: %v", colNames[i], v)
+		}
+	}
+
 	log.Info("Migration completed successfully!")
 }
+
+func extractData() ([][]any, []string, error) {
+	ctx, cancel := context.WithTimeout(context.Background(), 20*time.Second)
+	defer cancel()
+
+	pool, err := db.Connect(ctx, config.App.FromDb.Url)
+	defer db.Close(pool)
+	if err != nil {
+		log.Fatal(err)
+	}
+
+	log.Info("Successfully connected to from_db")
+	limit := 2
+
+	/* This query will become dinamyc later */
+	sql := `
+SELECT
+	id,
+	nombre_producto,
+	descripcion,
+	stock,
+	precio,
+	es_activo,
+	fecha_creacion,
+	ultima_actualizacion,
+	configuracion_json,
+	etiquetas,
+	binario_test,
+	ip_servidor,
+	rango_prueba
+FROM test.migration_test
+LIMIT $1;
+`
+
+	rows, err := pool.Query(ctx, sql, limit)
+	if err != nil {
+		if !errors.Is(err, pgx.ErrNoRows) {
+			return nil, nil, fmt.Errorf("Unexpected error: %w", err)
+		}
+
+		log.Warn("Unexpected error", err)
+		return [][]any{}, []string{}, nil
+	}
+	defer rows.Close()
+
+	cols := rows.FieldDescriptions()
+	for _, c := range cols {
+		log.Debugf("Column: %+v", c)
+	}
+
+	rowValues := make([][]any, 0, limit)
+
+	for rows.Next() {
+		values := make([]any, len(cols))
+		valuePtrs := make([]any, len(cols))
+
+		for i := range values {
+			valuePtrs[i] = &values[i]
+		}
+
+		rows.Scan(valuePtrs...)
+
+		rowValues = append(rowValues, values)
+	}
+
+	return rowValues, Map(cols, func(col pgconn.FieldDescription) string {
+		return col.Name
+	}), nil
+}
+
+func Map[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
+}