GORM：无法定位大型文本字段数据库 [英] GORM: mapping large text fields database agnostically

问题描述

我有一个可以针对SQL Server或Oracle后端运行的Grails应用程序。我使用GORM作为ORM。

我想以支持两种数据库类型的方式映射大型文本字段。在我的Grails领域类中，我有类似的东西：

  class Note {
字符串内容
 
 static constraint = {
 content nullable：false，blank：false 
} 
} 
  

然后我声明如下的数据库表：

   -  oracle 
 CREATE TABLE NOTE 
（
 id NUMBER（19，0）NOT NULL，
 version NUMBER（19，0）NOT NULL，
 content CLOB NOT NULL 
）; 
 
  -  SQL Server 
 CREATE TABLE NOTE 
（
 id NUMERIC（19，0）NOT NULL，
 version NUMERIC（19，0）NOT NULL，
 content NVARCHAR（MAX）NOT NULL 
）; 
  

GORM在启动时运行于 validate 模式，而且我无法找到Oracle和SQL Server数据类型和GORM映射的组合，这些映射允许没有GORM的存储或大型文本字段无法正确启动。

I已尝试：

• 在<$ c中将类型设置为 text $ c>映射，但这似乎不起作用。 Oracle抱怨期望 content 字段的类型为 long ，并且SQL Server需要一种<$ c $在这些情况下，你可以使用 。

code> clob ，它通过模式验证，但不允许我将字段设置为字符串值--GORM期望类型为 CLOB



我应该如何配置我的数据库定义和GORM才能使其工作？


解决方案

最终出现了一种解决方案：通过在启动时查询Grails配置，您可以选择适当的数据类型。



  class Note {
 
字符串内容
 
静态约束= {
 content nullable：false，blank：false 
} 
 
 static mappings = {
 content sqlType：DbSupport.bigStringType 
} 
 } 
 
 class DbSupport {
 
 static def getBigStringType（）{
 
 //检查选择哪个hibernate方言，并选择
 / /该数据库类型的适当类型映射：
 def dialect = ApplicationHolder.application.config.dataSource.dialect 
 switch（dialect）{
 
 caseorg.hibernate.dialect .SQLServerDialect：
 returnnvarchar
 break 
 
 caseorg.hibernate.dialect.O racle10gDialect：
 returnclob
 break 
} 
 
} 
} 
  




I have a Grails application that will run against either a SQL Server or Oracle backend. I am using GORM as an ORM.

I want to map a large text field in a way that supports both database types. In my Grails domain class I have something like:

class Note {
    String content

    static constraints = {
        content nullable: false, blank: false
    }
}

I then declare database tables that look like this:

-- oracle
CREATE TABLE NOTE 
(
    id NUMBER(19, 0) NOT NULL,
    version NUMBER(19, 0) NOT NULL,
    content CLOB NOT NULL
);

-- SQL Server
CREATE TABLE NOTE 
(
    id NUMERIC(19, 0) NOT NULL,
    version NUMERIC(19, 0) NOT NULL,
    content NVARCHAR(MAX) NOT NULL
);

GORM is running in validate mode on startup, and I can't find a combination of Oracle and SQL Server data types and GORM mappings that allow the storage or large text fields without GORM failing to start correctly.

I have tried:

• setting the type to text in mappings, but this doesn't seem to work. Oracle complains about expecting the content field to be of type long, and SQL Server wants a type of text in these circumstances.

• setting the type to clob, which passes schema validation but then doesn't allow me to set the field as a string value - GORM expects data of type CLOB.

How should I configure my database definitions and GORM to make this work?

解决方案

As hackish as it is, a solution eventually emerged: by querying the Grails configuration at startup time, you can select an appropriate data type.

class Note {

    String content

    static constraints = {
        content nullable: false, blank: false
    }

    static mappings = {
        content sqlType: DbSupport.bigStringType
    }
}

class DbSupport {

    static def getBigStringType() {

        // examine which hibernate dialect is selected, and pick
        // an appropriate type mapping for that database type:
        def dialect = ApplicationHolder.application.config.dataSource.dialect
        switch (dialect) {

            case "org.hibernate.dialect.SQLServerDialect":
                return "nvarchar"
                break

            case "org.hibernate.dialect.Oracle10gDialect":
                return "clob"
                break
        }

    }
}

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