GORM:不可知地映射大文本字段数据库 [英] GORM: mapping large text fields database agnostically

问题描述

我有一个 Grails 应用程序，可以在 SQL Server 或 Oracle 后端运行.我使用 GORM 作为 ORM.

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

我想以支持两种数据库类型的方式映射一个大文本字段.在我的 Grails 域类中，我有类似的东西:

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
    }
}

然后我声明如下所示的数据库表:

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 在启动时以 validate 模式运行，我找不到 Oracle 和 SQL Server 数据类型以及允许存储或大文本字段的 GORM 映射的组合，而 GORM 无法启动正确.

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.

我试过了:

• 在mappings 中将类型设置为text，但这似乎不起作用.Oracle 抱怨希望 content 字段的类型为 long，而 SQL Server 在这些情况下需要一种 text 类型.

• 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.

将 type 设置为 clob，它通过了模式验证，但不允许我将该字段设置为字符串值 - GORM 期望数据为输入 CLOB.

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.

我应该如何配置我的数据库定义和 GORM 以使其工作?

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

推荐答案

尽管很黑，但最终出现了一个解决方案:通过在启动时查询 Grails 配置，您可以选择合适的数据类型.

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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