HHH-12271 - SchemaDropperImpl does not drop constraints with IF EXISTS

hibernate-core/src/main/java/org/hibernate/tool/schema/internal/StandardForeignKeyExporter.java

@@ -145,8 +145,21 @@ public class StandardForeignKeyExporter implements Exporter<ForeignKey> {
 				dialect
 		);
 		return new String[] {
-				dialect.getAlterTableString( sourceTableName )
-						+ dialect.getDropForeignKeyString() + foreignKey.getName()
+				getSqlDropStrings( sourceTableName, foreignKey, dialect )
 		};
 	}
+
+	private String getSqlDropStrings(String tableName, ForeignKey foreignKey, Dialect dialect) {
+		final StringBuilder buf = new StringBuilder( dialect.getAlterTableString( tableName ) );
+		buf.append( dialect.getDropForeignKeyString() );
+		if ( dialect.supportsIfExistsBeforeConstraintName() ) {
+			buf.append( "if exists " );
+		}
+		buf.append( dialect.quote( foreignKey.getName() ) );
+		if ( dialect.supportsIfExistsAfterConstraintName() ) {
+			buf.append( " if exists" );
+		}
+		return buf.toString();
+	}
+
 }