Overwrite MySQL tables with AWS Glue

I ran into the same issue with Redshift, and the best solution we could come up with was to create a Java class that loads the MySQL driver and issues a truncate table:

package com.my.glue.utils.mysql;

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.SQLException;
import java.sql.Statement;

@SuppressWarnings("unused")
public class MySQLTruncateClient {
    public void truncate(String tableName, String url) throws SQLException, ClassNotFoundException {
        Class.forName("com.mysql.jdbc.Driver");
        try (Connection mysqlConnection = DriverManager.getConnection(url);
            Statement statement = mysqlConnection.createStatement()) {
            statement.execute(String.format("TRUNCATE TABLE %s", tableName));
        }
    }
}

Upload that JAR to S3 along with your MySQL Jar dependency and make your job dependent on those. In your PySpark script, you can load your truncate method with:

java_import(glue_context._jvm, "com.my.glue.utils.mysql.MySQLTruncateClient")
truncate_client = glue_context._jvm.MySQLTruncateClient()
truncate_client.truncate('my_table', 'jdbc:mysql://...')

The workaround I've come up with, which is a little simpler than the alternative posted, is the following:

• Create a staging table in mysql, and load your new data into this table.
• Run the command: REPLACE INTO myTable SELECT * FROM myStagingTable;
• Truncate the staging table

This can be done with:

import sys from awsglue.transforms
import * from awsglue.utils import getResolvedOptions
from pyspark.context import SparkContext
from awsglue.context import GlueContext
from awsglue.job import Job

## @params: [JOB_NAME]
args = getResolvedOptions(sys.argv, ['JOB_NAME'])

sc = SparkContext()
glueContext = GlueContext(sc)
spark = glueContext.spark_session
job = Job(glueContext)
job.init(args['JOB_NAME'], args)

import pymysql
pymysql.install_as_MySQLdb()
import MySQLdb
db = MySQLdb.connect("URL", "USERNAME", "PASSWORD", "DATABASE")
cursor = db.cursor()
cursor.execute("REPLACE INTO myTable SELECT * FROM myStagingTable")
cursor.fetchall()

db.close()
job.commit()

I found a simpler way working with JDBC connections in Glue. The way the Glue team recommends to truncate a table is via following sample code when you're writing data to your Redshift cluster:

datasink5 = glueContext.write_dynamic_frame.from_jdbc_conf(frame = resolvechoice4, catalog_connection = "<connection-name>", connection_options = {"dbtable": "<target-table>", "database": "testdb", "preactions":"TRUNCATE TABLE <table-name>"}, redshift_tmp_dir = args["TempDir"], transformation_ctx = "datasink5")

where

connection-name your Glue connection name to your Redshift Cluster
target-table    the table you're loading the data in 
testdb          name of the database 
table-name      name of the table to truncate (ideally the table you're loading into)