org.squashtest.tm.domain.jpql

Class HibernateDialectExtensions

java.lang.Object

org.squashtest.tm.domain.jpql.HibernateDialectExtensions

public class HibernateDialectExtensions
extends Object

This class defines some extensions to JPQL language, that must be registered in the HibernateSessionFactory, and can also be used in QueryDSL if needed.

group_concat

This section factory declares a custom function for the support of group_concat - which is not a JPQL standard function. The implementation for this custom function depends on the target database. See GroupConcatFunction for h2 and mysql, StringAggFunction for Postgre

Syntax is as follow :

• group_concat(col identifier)

  will concatenate as expected over the column identifier.

• group_concat(col identifier 1, 'order by', col identifier 2, ['asc|desc']) 

  will send this to the target db as 'group_concat(id1 order by id2 [asc|desc])'

Aggregate function wrappers

The standard aggregate functions : count, sum, avg, min and max, used in a JPA query, cannot apply on subqueries. For instance one cannot sum((select id from entity)). The antlr parser used by Hibernate will just dismiss such nodes although the would-be SQL would run just fine on the target database.

By chance custom sql function can do so. So, by registering the standard aggregate functions as custom functions we can trick Hibernate parser into thinking that the jpa item it reads is a custom function while it will just really print a regular function in the sql output, and so offer us free support for aggregate over subqueries.

The function names are :

• 's_avg',
• 's_sum',
• 's_min',
• 's_max',
• 's_count',

Those wrapper use distinct names so that the native aggregate functions are not overridden : depending on you needs you may use the regular 'count', or the corresponding wrapper 's_count'.

Author:

bsiri

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static class	HibernateDialectExtensions.FnSupport

Field Summary

Fields

Modifier and Type	Field and Description
static String	FN_NAME_AVG
static String	FN_NAME_CNT
static String	FN_NAME_GROUP_CONCAT
static String	FN_NAME_MAX
static String	FN_NAME_MIN
static String	FN_NAME_SUM
static String	FN_NAME_WEEK

Method Summary

Methods

Modifier and Type	Method and Description
static Map<String,org.hibernate.dialect.function.StandardSQLFunction>	getH2DialectExtensions()
static Map<String,org.hibernate.dialect.function.StandardSQLFunction>	getMysqlDialectExtensions()
static Map<String,org.hibernate.dialect.function.StandardSQLFunction>	getPostgresDialectExtensions()

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

FN_NAME_GROUP_CONCAT

public static final String FN_NAME_GROUP_CONCAT

See Also:

Constant Field Values

FN_NAME_WEEK

public static final String FN_NAME_WEEK

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Constant Field Values

FN_NAME_SUM

public static final String FN_NAME_SUM

See Also:

Constant Field Values

FN_NAME_CNT

public static final String FN_NAME_CNT

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Constant Field Values

FN_NAME_MIN

public static final String FN_NAME_MIN

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Constant Field Values

FN_NAME_MAX

public static final String FN_NAME_MAX

See Also:

Constant Field Values

FN_NAME_AVG

public static final String FN_NAME_AVG

See Also:

Constant Field Values

Method Detail

getMysqlDialectExtensions

public static Map<String,org.hibernate.dialect.function.StandardSQLFunction> getMysqlDialectExtensions()

getH2DialectExtensions

public static Map<String,org.hibernate.dialect.function.StandardSQLFunction> getH2DialectExtensions()

getPostgresDialectExtensions

public static Map<String,org.hibernate.dialect.function.StandardSQLFunction> getPostgresDialectExtensions()