Group items tagged

Entity–attribute–value model

Entity–attribute–value model (EAV) is a data model to describe entities where the number of attributes (properties, parameters) that can be used to describe them is potentially vast, but the number that will actually apply to a given entity is relatively modest

also known as object–attribute–value model, vertical database model and open schema

Composite identifier

You can define a composite primary key through several syntaxes:

@EmbeddedId

Mapping enum to database column using JPA/Hibernate You can use any of the 3 approaches discussed above. Map the enum to an integer column. The persistence implementation should automatically convert enum to ordinal() and back for you. Map the enum to a String column. The persistence implementation should automatically convert the enum value to String value via the name() function. Map the enum using a business value. You should mark the enum field as @Transient, and create another String field which you can map to a String column in your database table. Here’s an example code snippet. view plaincopy to clipboardprint?@Entity  public class Product {   @Column   private String colorValue;     @Transient   public Color getColor() {    return Color.fromValue(colorValue);   }     public void setColor(Color color) {    this.colorValue = color.toValue();   }  }  

Approach 3: Using a user defined business value – Recommended approach! This approach involves assigning a an explicit user defined value to each enum constant and defining a toValue() and fromValue() methods on the enum to do the serialization and deserialization.

public enum Color {   RED("RED"), GREEN("GREEN"), BLUE("BLUE"), UNKNOWN("UNKNOWN");     private final String value;     Color(String value) {     this.value = value;   }     public static Color fromValue(String value) {     if (value != null) {       for (Color color : values()) {         if (color.value.equals(value)) {           return color;         }       }     }       // you may return a default value     return getDefault();     // or throw an exception     // throw new IllegalArgumentException("Invalid color: " + value);   }     public String toValue() {     return value;   }     public static Color getDefault() {     return UNKNOWN;   }  }  public enum Color { RED("RED"), GREEN("GREEN"), BLUE("BLUE"), UNKNOWN("UNKNOWN"); private final String value; Color(String value) { this.value = value; } public static Color fromValue(String value) { if (value != null) { for (Color color : values()) { if (color.value.equals(value)) { return color; } } } // you may return a default value return getDefault(); // or throw an exception // throw new IllegalArgumentException("Invalid color: " + value); } public String toValue() { return value; } public static Color getDefault() { return UNKNOWN; } } This approach is better than approach 1 and approach 2 above. It neither depends on the order in which the enum constants are declared nor on the constant names.

Inheritance

hardest part of persisting inheritance is choosing how to represent the inheritance in the database

There are three inheritance strategies defined from the InheritanceType enum,

NO extra column in the join table

Use a common database user id, and manage auditing and security in the application

managed in the application by having an application user, and a single shared database user

adding a AUDIT_USER and AUDIT_TIMESTAMP column to all of the audited tables and auditUser and auditTimestamp field to all of the audited objects

used as a base class for JPA/Hibernate persisted permissions that wish to store the parts of the permission string in separate columns (e.g. 'domain', 'actions' and 'targets' columns)

Result Set Mapping

When a native SQL query returns objects, the SQL must ensure it returns the correct data to build the resultClass using the correct column names as specified in the mappings. If the SQL is more complex and returns different column names, or returns data for multiple objects then a @SqlResultSetMapping must be used.

@NamedNativeQuery

comment for a column

up to 1024 characters long

255 characters before MySQL 5.5.3

MySQL Error Number 1005 Can’t create table

(errno: 150)

SHOW ENGINE INNODB STATUS

Hibernate does not need a discriminator

It is allowed for

JOINED

AO_60DB71_SPRINT

SprintThis field is of type 'Sprint' and is available to all issue types.Searchable via JQL.

Has workflow "conditions" which prevent issues from being dragged freely between all columns.

Database Schema

Download the attached plugin: jira-schema-diagram-generator-plugin-1.0.jarInstall the plugin in your JIRA instance by following the instructions on Managing JIRA's Plugins.Go to the JIRA administration console and navigate to System > Troubleshooting and Support > Generate Schema Diagram Keyboard shortcut: g + g + start typing generateEnter the tables/columns to omit from the generated schema information, if desired.If you want to generate a pdf, enter the path to the Graphviz executable.Click Generate Schema.The 'Database Schema' page will be displayed with links to the schema file in txt, dot and pdf format.

Bi-directional Many to Many

object model can choose if it will be mapped in both directions

in which direction it will be mapped