diff --git a/go/binlog/binlog_entry.go b/go/binlog/binlog_entry.go
index bb70bc5..5650acc 100644
--- a/go/binlog/binlog_entry.go
+++ b/go/binlog/binlog_entry.go
@@ -26,7 +26,7 @@ func NewBinlogEntry(logFile string, logPos uint64) *BinlogEntry {
 	return binlogEntry
 }
 
-// NewBinlogEntry creates an empty, ready to go BinlogEntry object
+// NewBinlogEntryAt creates an empty, ready to go BinlogEntry object
 func NewBinlogEntryAt(coordinates mysql.BinlogCoordinates) *BinlogEntry {
 	binlogEntry := &BinlogEntry{
 		Coordinates: coordinates,
@@ -41,7 +41,7 @@ func (this *BinlogEntry) Duplicate() *BinlogEntry {
 	return binlogEntry
 }
 
-// Duplicate creates and returns a new binlog entry, with some of the attributes pre-assigned
+// String() returns a string representation of this binlog entry
 func (this *BinlogEntry) String() string {
 	return fmt.Sprintf("[BinlogEntry at %+v; dml:%+v]", this.Coordinates, this.DmlEvent)
 }
diff --git a/go/binlog/gomysql_reader.go b/go/binlog/gomysql_reader.go
index 106f73d..794d545 100644
--- a/go/binlog/gomysql_reader.go
+++ b/go/binlog/gomysql_reader.go
@@ -112,7 +112,7 @@ func (this *GoMySQLReader) handleRowsEvent(ev *replication.BinlogEvent, rowsEven
 				binlogEntry.DmlEvent.WhereColumnValues = sql.ToColumnValues(row)
 			}
 		}
-		// The channel will do the throttling. Whoever is reding from the channel
+		// The channel will do the throttling. Whoever is reading from the channel
 		// decides whether action is taken synchronously (meaning we wait before
 		// next iteration) or asynchronously (we keep pushing more events)
 		// In reality, reads will be synchronous
diff --git a/go/logic/applier.go b/go/logic/applier.go
index ee9e066..140b1a4 100644
--- a/go/logic/applier.go
+++ b/go/logic/applier.go
@@ -126,7 +126,6 @@ func (this *Applier) readTableColumns() (err error) {
 
 // showTableStatus returns the output of `show table status like '...'` command
 func (this *Applier) showTableStatus(tableName string) (rowMap sqlutils.RowMap) {
-	rowMap = nil
 	query := fmt.Sprintf(`show /* gh-ost */ table status from %s like '%s'`, sql.EscapeName(this.migrationContext.DatabaseName), tableName)
 	sqlutils.QueryRowsMap(this.db, query, func(m sqlutils.RowMap) error {
 		rowMap = m
@@ -482,6 +481,7 @@ func (this *Applier) ApplyIterationInsertQuery() (chunkSize int64, rowsAffected
 		if err != nil {
 			return nil, err
 		}
+		defer tx.Rollback()
 		sessionQuery := fmt.Sprintf(`SET
 			SESSION time_zone = '%s',
 			sql_mode = CONCAT(@@session.sql_mode, ',STRICT_ALL_TABLES')
@@ -1001,15 +1001,19 @@ func (this *Applier) ApplyDMLEventQuery(dmlEvent *binlog.BinlogDMLEvent) error {
 			if err != nil {
 				return err
 			}
+			rollback := func(err error) error {
+				tx.Rollback()
+				return err
+			}
 			sessionQuery := `SET
 			SESSION time_zone = '+00:00',
 			sql_mode = CONCAT(@@session.sql_mode, ',STRICT_ALL_TABLES')
 			`
 			if _, err := tx.Exec(sessionQuery); err != nil {
-				return err
+				return rollback(err)
 			}
 			if _, err := tx.Exec(buildResult.query, buildResult.args...); err != nil {
-				return err
+				return rollback(err)
 			}
 			if err := tx.Commit(); err != nil {
 				return err
diff --git a/go/logic/inspect.go b/go/logic/inspect.go
index 5f875a0..9b2da44 100644
--- a/go/logic/inspect.go
+++ b/go/logic/inspect.go
@@ -692,14 +692,17 @@ func (this *Inspector) getSharedColumns(originalColumns, ghostColumns *sql.Colum
 		for _, ghostColumn := range ghostColumns.Names() {
 			if strings.EqualFold(originalColumn, ghostColumn) {
 				isSharedColumn = true
+				break
 			}
 			if strings.EqualFold(columnRenameMap[originalColumn], ghostColumn) {
 				isSharedColumn = true
+				break
 			}
 		}
 		for droppedColumn := range this.migrationContext.DroppedColumnsMap {
 			if strings.EqualFold(originalColumn, droppedColumn) {
 				isSharedColumn = false
+				break
 			}
 		}
 		for _, virtualColumn := range originalVirtualColumns.Names() {
@@ -758,9 +761,8 @@ func (this *Inspector) getMasterConnectionConfig() (applierConfig *mysql.Connect
 }
 
 func (this *Inspector) getReplicationLag() (replicationLag time.Duration, err error) {
-	replicationLag, err = mysql.GetReplicationLag(
+	replicationLag, err = mysql.GetReplicationLagFromSlaveStatus(
 		this.informationSchemaDb,
-		this.migrationContext.InspectorConnectionConfig,
 	)
 	return replicationLag, err
 }
diff --git a/go/logic/migrator.go b/go/logic/migrator.go
index 4178f19..86de5ac 100644
--- a/go/logic/migrator.go
+++ b/go/logic/migrator.go
@@ -78,7 +78,7 @@ type Migrator struct {
 
 	rowCopyCompleteFlag int64
 	// copyRowsQueue should not be buffered; if buffered some non-damaging but
-	//  excessive work happens at the end of the iteration as new copy-jobs arrive befroe realizing the copy is complete
+	//  excessive work happens at the end of the iteration as new copy-jobs arrive before realizing the copy is complete
 	copyRowsQueue    chan tableWriteFunc
 	applyEventsQueue chan *applyEventStruct
 
diff --git a/go/logic/throttler.go b/go/logic/throttler.go
index 624956a..6f9f4bb 100644
--- a/go/logic/throttler.go
+++ b/go/logic/throttler.go
@@ -140,8 +140,8 @@ func (this *Throttler) collectReplicationLag(firstThrottlingCollected chan<- boo
 		if this.migrationContext.TestOnReplica || this.migrationContext.MigrateOnReplica {
 			// when running on replica, the heartbeat injection is also done on the replica.
 			// This means we will always get a good heartbeat value.
-			// When runnign on replica, we should instead check the `SHOW SLAVE STATUS` output.
-			if lag, err := mysql.GetReplicationLag(this.inspector.informationSchemaDb, this.inspector.connectionConfig); err != nil {
+			// When running on replica, we should instead check the `SHOW SLAVE STATUS` output.
+			if lag, err := mysql.GetReplicationLagFromSlaveStatus(this.inspector.informationSchemaDb); err != nil {
 				return log.Errore(err)
 			} else {
 				atomic.StoreInt64(&this.migrationContext.CurrentLag, int64(lag))
diff --git a/go/mysql/utils.go b/go/mysql/utils.go
index 67ed7f8..17bb5fc 100644
--- a/go/mysql/utils.go
+++ b/go/mysql/utils.go
@@ -58,9 +58,8 @@ func GetDB(migrationUuid string, mysql_uri string) (*gosql.DB, bool, error) {
 	return knownDBs[cacheKey], exists, nil
 }
 
-// GetReplicationLag returns replication lag for a given connection config; either by explicit query
-// or via SHOW SLAVE STATUS
-func GetReplicationLag(informationSchemaDb *gosql.DB, connectionConfig *ConnectionConfig) (replicationLag time.Duration, err error) {
+// GetReplicationLagFromSlaveStatus returns replication lag for a given db; via SHOW SLAVE STATUS
+func GetReplicationLagFromSlaveStatus(informationSchemaDb *gosql.DB) (replicationLag time.Duration, err error) {
 	err = sqlutils.QueryRowsMap(informationSchemaDb, `show slave status`, func(m sqlutils.RowMap) error {
 		slaveIORunning := m.GetString("Slave_IO_Running")
 		slaveSQLRunning := m.GetString("Slave_SQL_Running")
@@ -84,9 +83,6 @@ func GetMasterKeyFromSlaveStatus(connectionConfig *ConnectionConfig) (masterKey
 	}
 	defer db.Close()
 
-	if err != nil {
-		return nil, err
-	}
 	err = sqlutils.QueryRowsMap(db, `show slave status`, func(rowMap sqlutils.RowMap) error {
 		// We wish to recognize the case where the topology's master actually has replication configuration.
 		// This can happen when a DBA issues a `RESET SLAVE` instead of `RESET SLAVE ALL`.
@@ -99,7 +95,6 @@ func GetMasterKeyFromSlaveStatus(connectionConfig *ConnectionConfig) (masterKey
 		slaveIORunning := rowMap.GetString("Slave_IO_Running")
 		slaveSQLRunning := rowMap.GetString("Slave_SQL_Running")
 
-		//
 		if slaveIORunning != "Yes" || slaveSQLRunning != "Yes" {
 			return fmt.Errorf("Replication on %+v is broken: Slave_IO_Running: %s, Slave_SQL_Running: %s. Please make sure replication runs before using gh-ost.",
 				connectionConfig.Key,
diff --git a/go/sql/builder.go b/go/sql/builder.go
index c3a6229..2c5a7ae 100644
--- a/go/sql/builder.go
+++ b/go/sql/builder.go
@@ -140,13 +140,12 @@ func BuildRangeComparison(columns []string, values []string, args []interface{},
 	comparisons := []string{}
 
 	for i, column := range columns {
-		//
 		value := values[i]
 		rangeComparison, err := BuildValueComparison(column, value, comparisonSign)
 		if err != nil {
 			return "", explodedArgs, err
 		}
-		if len(columns[0:i]) > 0 {
+		if i > 0 {
 			equalitiesComparison, err := BuildEqualsComparison(columns[0:i], values[0:i])
 			if err != nil {
 				return "", explodedArgs, err