diff --git a/htdocs/core/modules/import/import_csv.modules.php b/htdocs/core/modules/import/import_csv.modules.php
index 60dc9bf6c15..34bff81e55c 100644
--- a/htdocs/core/modules/import/import_csv.modules.php
+++ b/htdocs/core/modules/import/import_csv.modules.php
@@ -633,6 +633,7 @@ class ImportCsv extends ModeleImports
 				//print 'listfields='.$listfields.'<br>listvalues='.$listvalues.'<br>';
 
 				// If no error for this $alias/$tablename, we have a complete $listfields and $listvalues that are defined
+				// so we can try to make the insert or update now.
 				if (! $errorforthistable)
 				{
 					//print "$alias/$tablename/$listfields/$listvalues<br>";
@@ -644,7 +645,7 @@ class ImportCsv extends ModeleImports
 						if (!empty($updatekeys)) {
 							// We do SELECT to get the rowid, if we already have the rowid, it's to be used below for related tables (extrafields)
 
-							if (empty($lastinsertid)) {
+							if (empty($lastinsertid)) {	// No insert done yet for a parent table
 								$sqlSelect = 'SELECT rowid FROM '.$tablename;
 
 								$data = array_combine($listfields, $listvalues);
@@ -680,10 +681,11 @@ class ImportCsv extends ModeleImports
 									$error++;
 								}
 							} else {
-								// We have a last INSERT ID. Check if we have a row referencing this foreign key.
+								// We have a last INSERT ID (got by previous pass), so we check if we have a row referencing this foreign key.
 								// This is required when updating table with some extrafields. When inserting a record in parent table, we can make
 								// a direct insert into subtable extrafields, but when me wake an update, the insertid is defined and the child record
-								// may already exists. So we rescan the extrafield table to be know if record exists or not for the rowid.
+								// may already exists. So we rescan the extrafield table to know if record exists or not for the rowid.
+								// Note: For extrafield tablename, we have in importfieldshidden_array an enty 'extra.fk_object'=>'lastrowid-tableparent' so $keyfield is 'fk_object'
 								$sqlSelect = 'SELECT rowid FROM '.$tablename;
 
 								if(empty($keyfield)) $keyfield = 'rowid';
diff --git a/htdocs/core/modules/import/import_xlsx.modules.php b/htdocs/core/modules/import/import_xlsx.modules.php
index 36b57e2d69a..2c37caa5d40 100644
--- a/htdocs/core/modules/import/import_xlsx.modules.php
+++ b/htdocs/core/modules/import/import_xlsx.modules.php
@@ -656,6 +656,7 @@ class ImportXlsx extends ModeleImports
 				//print 'listfields='.$listfields.'<br>listvalues='.$listvalues.'<br>';
 
 				// If no error for this $alias/$tablename, we have a complete $listfields and $listvalues that are defined
+				// so we can try to make the insert or update now.
 				if (! $errorforthistable)
 				{
 					//print "$alias/$tablename/$listfields/$listvalues<br>";
@@ -665,7 +666,8 @@ class ImportXlsx extends ModeleImports
 						$insertdone = false;
 						if (!empty($updatekeys)) {
 							// We do SELECT to get the rowid, if we already have the rowid, it's to be used below for related tables (extrafields)
-							if (empty($lastinsertid)) {
+
+							if (empty($lastinsertid)) {	// No insert done yet for a parent table
 								$sqlSelect = 'SELECT rowid FROM '.$tablename;
 
 								$data = array_combine($listfields, $listvalues);
@@ -704,7 +706,8 @@ class ImportXlsx extends ModeleImports
 								// We have a last INSERT ID. Check if we have a row referencing this foreign key.
 								// This is required when updating table with some extrafields. When inserting a record in parent table, we can make
 								// a direct insert into subtable extrafields, but when me wake an update, the insertid is defined and the child record
-								// may already exists. So we rescan the extrafield table to be know if record exists or not for the rowid.
+								// may already exists. So we rescan the extrafield table to know if record exists or not for the rowid.
+								// Note: For extrafield tablename, we have in importfieldshidden_array an enty 'extra.fk_object'=>'lastrowid-tableparent' so $keyfield is 'fk_object'
 								$sqlSelect = 'SELECT rowid FROM '.$tablename;
 
 								if(empty($keyfield)) $keyfield = 'rowid';