apache方解石找不到表 [英] table not found with apache calcite

问题描述

我正在尝试使用方解石做一些基本的事情，以了解框架.我设置了一个简单的示例，该示例应该从2个json文件中读取.我的模型看起来像

I am trying to do some basic things with calcite to understand the framework. I have setup a simple example that is supposed to read from 2 json files. My model looks like

{
  version: '1.0',
  defaultSchema: 'PEOPLE',
  schemas: [
    {
      name: 'PEOPLE',
      type: 'custom',
      factory: 'demo.JsonSchemaFactory',
      operand: {
        directory: '/..../calcite-json/src/test/resources/files'
      }
    }
  ]
}

在我的测试中，似乎可以很好地加载模型，因为当我提取数据库元数据信息时，可以看到文件正在作为PEOPLE模式下的表加载.但是在那条语句之后，我正尝试从该表中执行select *，但收到一条错误消息，即未找到该表.

In my test, it seems that the model is being loaded fine because when I pull the database metadata information, I can see that my file is being loaded as a table under PEOPLE schema. But then right after that statement I am trying to do a select * from that table and I get an error that table was not found.

> --
null
PEOPLE
a
TABLE
-->
Jun 29, 2015 8:53:30 AM org.apache.calcite.sql.validate.SqlValidatorException <init>
SEVERE: org.apache.calcite.sql.validate.SqlValidatorException: Table 'A' not found
Jun 29, 2015 8:53:30 AM org.apache.calcite.runtime.CalciteException <init>
SEVERE: org.apache.calcite.runtime.CalciteContextException: At line 1, column 26: Table 'A' not found

输出的第一行显示数据库元数据-null PEOPLE a TABLE->"中的表.这表明表"a"存在于模式"people"下，并且类型为"table".

The first line in the output shows the tables from database metadata "-- null PEOPLE a TABLE -->". This shows that a table "a" is present under schema "people" and is of the type "table".

我的测试代码如下

@Test
public void testModel() throws SQLException {
    Properties props = new Properties();
    props.put("model", getPath("/model.json"));
    System.out.println("model = " + props.get("model"));
    Connection conn = DriverManager.getConnection("jdbc:calcite:", props);

    DatabaseMetaData md = conn.getMetaData();
    ResultSet tables = md.getTables(null, "PEOPLE", "%", null);
    while (tables.next()) {
        System.out.println("--");
        System.out.println(tables.getString(1));
        System.out.println(tables.getString(2));
        System.out.println(tables.getString(3));
        System.out.println(tables.getString(4));
        System.out.println("-->");
    }

    Statement stat = conn.createStatement();
    stat.execute("select _MAP['name'] from a");

    stat.close();
    conn.close();
}

有什么想法为什么我无法在已加载的表格上进行选择?

Any ideas why I am not able to do a select on the loaded table?

我注意到的另一件有趣的事情是，对于1个文件，Schema.getTableMap被调用了4次.

Another interesting thing I noticed is that for 1 file, Schema.getTableMap is being called 4 times.

可以在github上的找到完整的项目代码

The complete code for the project can be found on github

推荐答案

问题是区分大小写.由于您没有将表名括在双引号中，因此Calcite的SQL解析器将其转换为大写.因为该文件名为"a.json"，所以该表也称为"a"，而您的查询正在寻找一个名为"A"的表.

The problem is case-sensitivity. Because you did not enclose the table name in double-quotes, Calcite's SQL parser converted it to upper case. Because the file is called 'a.json', the table is also called 'a', whereas your query is looking for a table called 'A'.

解决方案是按如下方式编写查询:

The solution is to write your query as follows:

select _MAP['name'] from "a"

它变成:

stat.execute("select _MAP['name'] from \"a\"");

当您将其嵌入Java中时.

when you embed it in Java.

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