Question

我有以下变更集：

ax.get_xlim()

我想检查是否已存在唯一约束：

<changeSet author="test" id="1517488978218-28">
    <addUniqueConstraint columnNames="name_" constraintName="UK_52q0nm9af3039btfxjt8q6ahj" tableName="settings_table"/>
</changeSet>

但它不起作用，因为我不知道数据库名称。我需要在SQL查询中获取数据库名称，我该如何获取它？我的数据源初始化代码：

<preConditions onFail="MARK_RAN">
    <sqlCheck expectedResult="0">select distinct CONSTRAINT_NAME from information_schema.TABLE_CONSTRAINTS where constraint_type = 'UNIQUE' AND  CONSTRAINT_NAME ='UK_52q0nm9af3039btfxjt8q6ahj' AND table_schema = '${databasename}'</sqlCheck>
</preConditions>

Answer 1

我写下以下CustomPrecondition：

public class UniqueConstraintExists implements CustomPrecondition {

    private String constraintName;
    private String tableName;

    public void setConstraintName(String constraintName) {
        this.constraintName = constraintName;
    }

    public void setTableName(String tableName) {
        this.tableName = tableName;
    }

    @Override
    public void check(Database database) throws CustomPreconditionFailedException, CustomPreconditionErrorException {

        if(database instanceof MySQLDatabase){

            String defaultCatalogName = database.getDefaultCatalogName();

            String sql = String.format("select count(distinct CONSTRAINT_NAME) " +
                            "from information_schema.TABLE_CONSTRAINTS " +
                            "where constraint_type = 'UNIQUE' AND CONSTRAINT_NAME ='%s' AND TABLE_NAME='%s' AND table_schema = '%s'",
                    constraintName, tableName, defaultCatalogName);

            RawSqlStatement statement = new RawSqlStatement(sql);

            int count = 0;

            try {
                count = ExecutorService.getInstance().getExecutor(database).queryForInt(statement);
            } catch (DatabaseException e) {
                throw new CustomPreconditionErrorException("Unique constraint " + constraintName + " get count exception",e);
            }

            if(count == 1){
                //exists
                return;
            }else if(count == 0){
                //not exists
                throw new CustomPreconditionFailedException(String.format("Unique constraint %s not exists", constraintName));
            }else{
                //impossible
                throw new CustomPreconditionErrorException("Count of constraint instances " + constraintName + " more than 1 or less than 0, count: " + count);
            }

        }

        throw new CustomPreconditionErrorException("Unsupported database for UniqueConstraintExists precondition: " + database.getDatabaseProductName() + ", mysql and mariadb are only supported");
    }
}

变更集：

<changeSet author="macmonitor.by" id="1517488978218-28">
        <preConditions onFail="MARK_RAN">
            <not>
                <customPrecondition className="by.macmonitor.liquibase.UniqueConstraintExists">
                    <param name="constraintName" value="UK_52q0nm9af3039btfxjt8q6ahj"/>
                    <param name="tableName" value="settings_table"/>
                </customPrecondition>
            </not>
        </preConditions>
        <addUniqueConstraint columnNames="name_" constraintName="UK_52q0nm9af3039btfxjt8q6ahj"
                             tableName="settings_table"/>
</changeSet>

liquibase precondition sqlCheck获取数据库名称

1 个答案: