6. Calcite添加自定义函数

1. 简介

在上篇博文中介绍了如何使用calcite进行sql验证, 但是真正在实际生产环境中我们可能需要使用到

用户自定义函数(UDF): 通过代码实现对应的函数逻辑并注册给calcite
- sql验证: 将UDF信息注册给calcite, SqlValidator.validator验证阶段即可通过验证
- sql执行: calcite通过调用UDF逻辑实现函数逻辑
自定义db函数: 数据库中创建的自定义函数
- sql验证: 将自定义的db函数信息注册给calcite, SqlValidator.validator验证阶段即可通过验证
- sql执行: 下推到db执行对应的db函数

此时我们需要将自定义的函数注册到calcite中, 用于sql验证和执行. 例如注册一个简单的函数如: 将数据库中的性别字段值做字典转换.

2. Maven

<dependency>

    <groupId>org.apache.calcite</groupId>

    <artifactId>calcite-core</artifactId>

    <version>1.37.0</version>

</dependency>

<dependency>

    <groupId>mysql</groupId>

    <artifactId>mysql-connector-java</artifactId>

    <version>8.0.33</version>

</dependency>

2. UDF

如上述所说, UDF是将用户自定义的方法注册为函数使用的, 首先看一下calcite是如何注册UDF的

SchemaPlus#add(String name, Function function);

其Function的实现类如下:

定义UDF实现

public class Udf {

    public static String dictSex(String code) {

        if (StringUtils.isBlank(code)) {

            return code;

        }

        if (StringUtils.equals(code, "1")) {

            return "男";

        } else if (StringUtils.equals(code, "2")) {

            return "女";

        }

        else {

            return "未知";

        }

    }

}

把dictSex方法注册到calcite中, 因为上述的方法输入返回的都是单一值, 所以直接注册为标量函数即可(如果是聚合函数可以使用AggregateFunction)
```
// 指定函数名称 和 对应函数的class & method name

rootSchema.add("dict_sex", ScalarFunctionImpl.create(Udf.class, "dictSex"));
```

测试执行

final ResultSet resultSet = statement.executeQuery("SELECT username, dict_sex(sex) sex_name FROM `user`");

printResultSet(resultSet);

表数据如下

输出结果

c.l.c.CalciteFuncTest - [printResultSet,86] - Number of columns: 2

c.l.c.CalciteFuncTest - [printResultSet,98] - {sex_name=男, username=张三}

c.l.c.CalciteFuncTest - [printResultSet,98] - {sex_name=女, username=李四}

c.l.c.CalciteFuncTest - [printResultSet,98] - {sex_name=女, username=张铁牛}

3. 自定义db函数

首先我们定义一个db 函数实现字典值的转换

DELIMITER //

CREATE FUNCTION dict_sex(code VARCHAR(10))

RETURNS VARCHAR(10)

DETERMINISTIC

BEGIN

    -- 如果code为空或只包含空白字符，则直接返回code

    IF code IS NULL OR TRIM(code) = '' THEN

        RETURN code;

    END IF;

    -- 如果code为'1'则返回'男'

    IF code = '1' THEN

        RETURN '男';

    -- 如果code为'2'则返回'女'

    ELSEIF code = '2' THEN

        RETURN '女';

    ELSE

        RETURN '未知';

    END IF;

END //

DELIMITER ;

验证函数功能

ok, 函数创建完成, 我们将函数注册到calcite中

calcite中sqlfunction有很多其已经实现的类, 我们这里使用SqlBasicFunction来创建我们的函数

定义SqlFunction

/*

 * SqlBasicFunction create(String name, SqlReturnTypeInference returnTypeInference, SqlOperandTypeChecker operandTypeChecker)

 * name: 函数名称

 * returnTypeInference: 返回值类型

 * operandTypeChecker: 函数入参的校验器

 */

SqlFunction DICT_SEX = SqlBasicFunction.create("dict_sex", ReturnTypes.VARCHAR, OperandTypes.family(SqlTypeFamily.CHARACTER));

注册SqlFunction

从上篇博文中我们知道, calcite的sql函数都注册到了SqlStdOperatorTable类中, 所以我们只需要将自定义的函数注册进即可

final SqlStdOperatorTable sqlStdOperatorTable = SqlStdOperatorTable.instance();

sqlStdOperatorTable.register(DICT_SEX);

对, 就这么简单. 因为SqlStdOperatorTable类是单例模式, 所以我们可以随时随地的进行注册, 其验证逻辑就可以直接调用了

当然, 看了其他博客大多数都是继承SqlStdOperatorTable类实现自定义SqlStdOperatorTable的如下, 最后使用自己的SqlStdOperatorTable即可

public static class SqlCustomOperatorTable extends SqlStdOperatorTable {

    private static SqlCustomOperatorTable instance;

    // 只需要申明为成员变量即可, instance.init() 的时候会反射取变量进行注册

    public static final SqlFunction DICT_SEX = SqlBasicFunction.create("dict_sex", ReturnTypes.VARCHAR, OperandTypes.family(SqlTypeFamily.CHARACTER));

    public static synchronized SqlCustomOperatorTable instance() {

        if (instance == null) {

            instance = new SqlCustomOperatorTable();

            instance.init();

        }

        return instance;

    }

    /**

     * 如果想修改获取函数的过程, 可以重写此方法

     */

    @Override

    protected void lookUpOperators(String name, boolean caseSensitive, Consumer<SqlOperator> consumer) {

        super.lookUpOperators(name, caseSensitive, consumer);

    }

}

测试执行

final ResultSet resultSet = statement.executeQuery("SELECT username, dict_sex(sex) sex_name FROM `user`");

printResultSet(resultSet);

输出结果

c.l.c.CalciteFuncTest - [printResultSet,86] - Number of columns: 2

c.l.c.CalciteFuncTest - [printResultSet,98] - {sex_name=男, username=张三}

c.l.c.CalciteFuncTest - [printResultSet,98] - {sex_name=女, username=李四}

c.l.c.CalciteFuncTest - [printResultSet,98] - {sex_name=女, username=张铁牛}

经测试: 如果udf 和 sqlfunction 同时存在的时候优先使用udf

4. 完整代码

4.1 udf

package com.ldx.calcite;

import com.google.common.collect.Maps;

import com.mysql.cj.jdbc.MysqlDataSource;

import lombok.SneakyThrows;

import lombok.extern.slf4j.Slf4j;

import org.apache.calcite.adapter.jdbc.JdbcSchema;

import org.apache.calcite.config.Lex;

import org.apache.calcite.jdbc.CalciteConnection;

import org.apache.calcite.schema.SchemaPlus;

import org.apache.calcite.schema.impl.ScalarFunctionImpl;

import org.junit.jupiter.api.BeforeAll;

import org.junit.jupiter.api.Test;

import javax.sql.DataSource;

import java.sql.Connection;

import java.sql.DriverManager;

import java.sql.ResultSet;

import java.sql.ResultSetMetaData;

import java.sql.SQLException;

import java.sql.Statement;

import java.util.Map;

import java.util.Properties;

import static org.apache.calcite.config.CalciteConnectionProperty.LEX;

@Slf4j

public class CalciteFuncWithUdfTest {

    private static Statement statement;

    @BeforeAll

    @SneakyThrows

    public static void beforeAll() {

        Properties info = new Properties();

        // 不区分sql大小写

        info.setProperty("caseSensitive", "false");

        info.setProperty(LEX.camelName(), Lex.MYSQL.name());

        // 创建Calcite连接

        Connection connection = DriverManager.getConnection("jdbc:calcite:", info);

        CalciteConnection calciteConnection = connection.unwrap(CalciteConnection.class);

        // 构建RootSchema，在Calcite中，RootSchema是所有数据源schema的parent，多个不同数据源schema可以挂在同一个RootSchema下

        SchemaPlus rootSchema = calciteConnection.getRootSchema();

        // 设置默认的schema, 如果不设置sql中需要加上对应数据源的名称

        calciteConnection.setSchema("my_mysql");

        final DataSource mysqlDataSource = getMysqlDataSource();

        final JdbcSchema schemaWithMysql = JdbcSchema.create(rootSchema, "my_mysql", mysqlDataSource, "test", null);

        final SchemaPlus myMysqlSchema = rootSchema.add("my_mysql", schemaWithMysql);

        // 全局注册

        rootSchema.add("dict_sex", ScalarFunctionImpl.create(Udf.class, "dictSex"));

        statement = calciteConnection.createStatement();

        // 只注册到mysql schema中

        // myMysqlSchema.add("dict_sex", ScalarFunctionImpl.create(Udf.class, "dictSex"));

        // 创建SQL语句执行查询

        statement = calciteConnection.createStatement();

    }

    @Test

    @SneakyThrows

    public void test_udf_func() {

        final ResultSet resultSet = statement.executeQuery("SELECT username, dict_sex(sex) sex_name FROM `user`");

        printResultSet(resultSet);

    }

    private static DataSource getMysqlDataSource() {

        MysqlDataSource dataSource = new MysqlDataSource();

        dataSource.setUrl("jdbc:mysql://localhost:3306/test");

        dataSource.setUser("root");

        dataSource.setPassword("123456");

        return dataSource;

    }

    public static void printResultSet(ResultSet resultSet) throws SQLException {

        // 获取 ResultSet 元数据

        ResultSetMetaData metaData = resultSet.getMetaData();

        // 获取列数

        int columnCount = metaData.getColumnCount();

        log.info("Number of columns: {}",columnCount);

        // 遍历 ResultSet 并打印结果

        while (resultSet.next()) {

            final Map<String, String> item = Maps.newHashMap();

            // 遍历每一列并打印

            for (int i = 1; i <= columnCount; i++) {

                String columnName = metaData.getColumnName(i);

                String columnValue = resultSet.getString(i);

                item.put(columnName, columnValue);

            }

            log.info(item.toString());

        }

    }

}

4.2 db func

package com.ldx.calcite;

import com.google.common.collect.Maps;

import com.mysql.cj.jdbc.MysqlDataSource;

import lombok.SneakyThrows;

import lombok.extern.slf4j.Slf4j;

import org.apache.calcite.adapter.jdbc.JdbcSchema;

import org.apache.calcite.config.Lex;

import org.apache.calcite.jdbc.CalciteConnection;

import org.apache.calcite.schema.SchemaPlus;

import org.apache.calcite.sql.SqlBasicFunction;

import org.apache.calcite.sql.SqlFunction;

import org.apache.calcite.sql.SqlOperator;

import org.apache.calcite.sql.fun.SqlStdOperatorTable;

import org.apache.calcite.sql.type.OperandTypes;

import org.apache.calcite.sql.type.ReturnTypes;

import org.apache.calcite.sql.type.SqlTypeFamily;

import org.junit.jupiter.api.BeforeAll;

import org.junit.jupiter.api.Test;

import javax.sql.DataSource;

import java.sql.Connection;

import java.sql.DriverManager;

import java.sql.ResultSet;

import java.sql.ResultSetMetaData;

import java.sql.SQLException;

import java.sql.Statement;

import java.util.Map;

import java.util.Properties;

import java.util.function.Consumer;

import static org.apache.calcite.config.CalciteConnectionProperty.LEX;

@Slf4j

public class CalciteFuncWithDbTest {

    private static Statement statement;

    public static final SqlFunction DICT_SEX = SqlBasicFunction.create("dict_sex", ReturnTypes.VARCHAR, OperandTypes.family(SqlTypeFamily.CHARACTER));

    @BeforeAll

    @SneakyThrows

    public static void beforeAll() {

        Properties info = new Properties();

        // 不区分sql大小写

        info.setProperty("caseSensitive", "false");

        info.setProperty(LEX.camelName(), Lex.MYSQL.name());

        // 创建Calcite连接

        Connection connection = DriverManager.getConnection("jdbc:calcite:", info);

        CalciteConnection calciteConnection = connection.unwrap(CalciteConnection.class);

        // 构建RootSchema，在Calcite中，RootSchema是所有数据源schema的parent，多个不同数据源schema可以挂在同一个RootSchema下

        SchemaPlus rootSchema = calciteConnection.getRootSchema();

        // 设置默认的schema, 如果不设置sql中需要加上对应数据源的名称

        calciteConnection.setSchema("my_mysql");

        final DataSource mysqlDataSource = getMysqlDataSource();

        final JdbcSchema schemaWithMysql = JdbcSchema.create(rootSchema, "my_mysql", mysqlDataSource, "test", null);

        rootSchema.add("my_mysql", schemaWithMysql);

        final SqlStdOperatorTable sqlStdOperatorTable = SqlStdOperatorTable.instance();

        sqlStdOperatorTable.register(DICT_SEX);

        statement = calciteConnection.createStatement();

    }

    @Test

    @SneakyThrows

    public void test_db_func() {

        final ResultSet resultSet = statement.executeQuery("SELECT dict_sex(sex) sex_name FROM `user`");

        printResultSet(resultSet);

    }

    private static DataSource getMysqlDataSource() {

        MysqlDataSource dataSource = new MysqlDataSource();

        dataSource.setUrl("jdbc:mysql://localhost:3306/test");

        dataSource.setUser("root");

        dataSource.setPassword("123456");

        return dataSource;

    }

    public static void printResultSet(ResultSet resultSet) throws SQLException {

        // 获取 ResultSet 元数据

        ResultSetMetaData metaData = resultSet.getMetaData();

        // 获取列数

        int columnCount = metaData.getColumnCount();

        log.info("Number of columns: {}",columnCount);

        while (resultSet.next()) {

            final Map<String, String> item = Maps.newHashMap();

            // 遍历每一列并打印

            for (int i = 1; i <= columnCount; i++) {

                String columnName = metaData.getColumnName(i);

                String columnValue = resultSet.getString(i);

                item.put(columnName, columnValue);

            }

            log.info(item.toString());

        }

    }

    public static class SqlCustomOperatorTable extends SqlStdOperatorTable {

        private static SqlCustomOperatorTable instance;

        // 只需要申明为成员变量即可, instance.init() 的时候会反射取变量进行注册

        public static final SqlFunction DICT_SEX = SqlBasicFunction.create("dict_sex", ReturnTypes.VARCHAR, OperandTypes.family(SqlTypeFamily.CHARACTER));

        public static synchronized SqlCustomOperatorTable instance() {

            if (instance == null) {

                instance = new SqlCustomOperatorTable();

                instance.init();

            }

            return instance;

        }

        /**

         * 如果想修改获取函数的过程, 可以重写此方法

         */

        @Override

        protected void lookUpOperators(String name, boolean caseSensitive, Consumer<SqlOperator> consumer) {

            super.lookUpOperators(name, caseSensitive, consumer);

        }

    }

}