feat: implement MSSQL data extraction and transformation process

cmd/go_migrate/process.go

@@ -1,7 +1,10 @@
 package main
 
 import (
+	"context"
 	"database/sql"
+	"fmt"
+
 	"github.com/jackc/pgx/v5/pgxpool"
 
 	_ "github.com/microsoft/go-mssqldb"
@@ -17,12 +20,16 @@ func processMigrationJob(sourceDb *sql.DB, targetDb *pgxpool.Pool, job Migration
 	logColumnTypes(sourceColTypes, "Source col types")
 	logColumnTypes(targetColTypes, "Target col types")
 
-	sourceQuery := buildExtractQueryMssql(job, sourceColTypes)
+	chRowsExtract := make(chan []UnknownRowValues, QueueSize)
 
-	log.Debug(sourceQuery)
+	mssqlContext := context.Background()
 
-	targetQuery := buildExtractQueryPostgres(job, targetColTypes)
-	log.Debug(targetQuery)
+	if err := extractFromMssql(mssqlContext, job, sourceColTypes, ChunkSize, sourceDb, chRowsExtract); err != nil {
+		log.Fatal("Unexpected error extrating data from mssql: ", err)
+	}
+	close(chRowsExtract)
+
+	transformRowsMssql(job, sourceColTypes, chRowsExtract)
 }
 
 func logColumnTypes(columnTypes []ColumnType, label string) {
@@ -32,3 +39,22 @@ func logColumnTypes(columnTypes []ColumnType, label string) {
 		log.Infof("%+v", col)
 	}
 }
+
+func transformRowsMssql(job MigrationJob, columns []ColumnType, in <-chan []UnknownRowValues) {
+	for rows := range in {
+		log.Debug("Chunk received, transforming...")
+
+		for i, rowValues := range rows {
+			if i%100 == 0 {
+				logSampleRow(job, columns, rowValues, fmt.Sprintf("row %d", i))
+			}
+		}
+	}
+}
+
+func logSampleRow(job MigrationJob, columns []ColumnType, rowValues UnknownRowValues, tag string) {
+	log.Infof("[%s.%s] Sample row: (%s)", job.Schema, job.Table, tag)
+	for i, col := range columns {
+		log.Infof("%s: %v", col.Name(), rowValues[i])
+	}
+}