Added java comments

Author: Abdelrahman Mostafa

src/main/java/org/jabref/logic/search/indexing/BibFieldsIndexer.java

@@ -310,7 +310,10 @@ private void insertField(BibEntry entry, Field field) {
                 FIELD_NAME,
                 FIELD_VALUE_LITERAL,
                 FIELD_VALUE_TRANSFORMED);
-        // Inserts a new record into the table, or updates the existing record if there's a conflict
+
+        // Inserts or updates date-related fields (e.g., date, year, month, day) into the index.
+        // If a conflict occurs (e.g., the same ENTRY_ID and FIELD_NAME already exist),
+        // the existing values are overwritten with the new ones to ensure the latest data is stored.
         String insertDateFieldQuery = """
                 INSERT INTO %s ("%s", "%s", "%s", "%s")
                 VALUES (?, ?, ?, ?)
@@ -325,8 +328,9 @@ ON CONFLICT ("%s", "%s")
                 ENTRY_ID, FIELD_NAME,
                 FIELD_VALUE_LITERAL, FIELD_VALUE_LITERAL,
                 FIELD_VALUE_TRANSFORMED, FIELD_VALUE_TRANSFORMED);
+
         String entryId = entry.getId();
-        // If the updated field is date-related, re-index all date fields to overwrite the previous value.
+        // If the updated field is date-related,iterate through all date fields and update the index accordingly.
         if (dateFields.contains(field)) {
             try (PreparedStatement preparedStatement = connection.prepareStatement(insertDateFieldQuery)) {
                 for (Field dateField : dateFields) {

src/main/java/org/jabref/model/search/PostgreConstants.java

@@ -63,6 +63,10 @@ public static String getMainTableSchemaReference(String mainTable) {
         return BIB_FIELDS_SCHEME + ".\"" + mainTable + "\"";
     }
 
+    /**
+     * Generates the schema reference for the split table, which is used to store multi-value fields (e.g., authors, keywords)
+     * in a normalized form to facilitate efficient querying and indexing of the data.
+     */
     public static String getSplitTableSchemaReference(String mainTable) {
         return BIB_FIELDS_SCHEME + ".\"" + mainTable + SPLIT_TABLE_SUFFIX + "\"";
     }