fix: primary key backing index issues.

src/main/java/liquibase/ext/hibernate/diff/ChangedPrimaryKeyChangeGenerator.java

@@ -0,0 +1,37 @@
+package liquibase.ext.hibernate.diff;
+
+import liquibase.change.Change;
+import liquibase.database.Database;
+import liquibase.diff.ObjectDifferences;
+import liquibase.diff.output.DiffOutputControl;
+import liquibase.diff.output.changelog.ChangeGeneratorChain;
+import liquibase.ext.hibernate.database.HibernateDatabase;
+import liquibase.structure.DatabaseObject;
+import liquibase.structure.core.PrimaryKey;
+
+/**
+ * Hibernate doesn't know about all the variations that occur with primary keys, especially backing index stuff.
+ * To prevent changing customized primary keys, we suppress this kind of changes from hibernate side.
+ */
+public class ChangedPrimaryKeyChangeGenerator extends liquibase.diff.output.changelog.core.ChangedPrimaryKeyChangeGenerator {
+
+    @Override
+    public int getPriority(Class<? extends DatabaseObject> objectType, Database database) {
+        if (PrimaryKey.class.isAssignableFrom(objectType)) {
+            return PRIORITY_ADDITIONAL;
+        }
+        return PRIORITY_NONE;
+    }
+
+    @Override
+    public Change[] fixChanged(DatabaseObject changedObject, ObjectDifferences differences, DiffOutputControl control, Database referenceDatabase, Database comparisonDatabase, ChangeGeneratorChain chain) {
+        if (referenceDatabase instanceof HibernateDatabase || comparisonDatabase instanceof HibernateDatabase) {
+            differences.removeDifference("unique");
+            if (!differences.hasDifferences()) {
+                return null;
+            }
+        }
+
+        return super.fixChanged(changedObject, differences, control, referenceDatabase, comparisonDatabase, chain);
+    }
+}

src/main/java/liquibase/ext/hibernate/diff/ChangedUniqueConstraintChangeGenerator.java

@@ -9,6 +9,11 @@
 import liquibase.structure.DatabaseObject;
 import liquibase.structure.core.UniqueConstraint;
 
+/**
+ * Unique attribute for unique constraints backing index can have different values dependending on the database implementation,
+ * so we suppress all unique constraint changes based on unique constraints.
+
+ */
 public class ChangedUniqueConstraintChangeGenerator extends liquibase.diff.output.changelog.core.ChangedUniqueConstraintChangeGenerator {
 
     @Override

src/main/resources/META-INF/services/liquibase.diff.output.changelog.ChangeGenerator

@@ -1,5 +1,6 @@
 liquibase.ext.hibernate.diff.ChangedColumnChangeGenerator
 liquibase.ext.hibernate.diff.ChangedForeignKeyChangeGenerator
+liquibase.ext.hibernate.diff.ChangedPrimaryKeyChangeGenerator
 liquibase.ext.hibernate.diff.ChangedSequenceChangeGenerator
 liquibase.ext.hibernate.diff.ChangedUniqueConstraintChangeGenerator
 liquibase.ext.hibernate.diff.MissingSequenceChangeGenerator