Skip to main content

mysql execute immediate

I had a requirement to generate a sharded schema where no of shards and no of tables in the shard were dynamic. Basically we wanted to shard one table so we ended up creating 8 schemas and each schema will hold 8 tables that are copy of the same schema. Now I didnt wanted to hand write the 64 table/schema creation statement so came up with this procedure that allows to dynamically build and execute sql queries.  Oracle was so easy, mysql is a little bit verbose.

    drop procedure if exists create_rdb_tables;
    delimiter #
    create procedure create_rdb_tables()
    declare v_max int unsigned default 9;
    declare v_counteri int unsigned default 1;
    declare v_counterj int unsigned default 1;
      while v_counteri < v_max do
        while v_counterj < v_max do
            set @sql_text := concat('drop table if exists metadata_rdb_schema',v_counteri, '.metadata_rdb_t', v_counterj,';');
            prepare stmt from @sql_text;
            execute stmt;
            DEALLOCATE PREPARE stmt;
            set @sql_text := concat('CREATE TABLE metadata_rdb_schema',v_counteri, '.metadata_rdb_t', v_counterj, ' (user_id INT NOT NULL, object_id VARCHAR(255) NOT NULL,group_id VARCHAR(36) NOT NULL,entry_id VARCHAR(36) NOT NULL,created_time DATETIME NOT NULL, primary key(object_id))TYPE=innodb;');
            prepare stmt from @sql_text;
            execute stmt;
            DEALLOCATE PREPARE stmt;
            set v_counterj=v_counterj+1;
        end while;
       set v_counteri=v_counteri+1;
      end while;
    end #
    delimiter ;
    call create_rdb_tables();
    drop procedure if exists create_rdb_tables; 

Finally it started becoming messy and kludgy so I ended up writing clean python code to generate the ddl :). This effort was a waste but I ended up learning how to do dynamic sql execution in mysql.


Popular posts from this blog

RabbitMQ java clients for beginners

Here is a sample of a consumer and producer example for RabbitMQ. The steps are
Download ErlangDownload Rabbit MQ ServerDownload Rabbit MQ Java client jarsCompile and run the below two class and you are done.
This sample create a Durable Exchange, Queue and a Message. You will have to start the consumer first before you start the for the first time.

For more information on AMQP, Exchanges, Queues, read this excellent tutorial
import com.rabbitmq.client.Connection; import com.rabbitmq.client.Channel; import com.rabbitmq.client.*; public class RabbitMQProducer { public static void main(String []args) throws Exception { ConnectionFactory factory = new ConnectionFactory(); factory.setUsername("guest"); factory.setPassword("guest"); factory.setVirtualHost("/"); factory.setHost(""); factory.setPort(5672); Conne…

Logging to Graphite monitoring tool from java

We use Graphite as a tool for monitoring some stats and watch trends. A requirement is to monitor impact of new releases as build is deployed to app nodes to see if things like
1) Has the memcache usage increased.
2) Has the no of Java exceptions went up.
3) Is the app using more tomcat threads.
Here is a screenshot

We changed the installer to log a deploy event when a new build is deployed. I wrote a simple spring bean to log graphite events using java. Logging to graphite is easy, all you need to do is open a socket and send lines of events.
import org.slf4j.Logger;import org.slf4j.LoggerFactory; import; import; import; import java.util.HashMap; import java.util.Map; public class GraphiteLogger { private static final Logger logger = LoggerFactory.getLogger(GraphiteLogger.class); private String graphiteHost; private int graphitePort; public String getGraphiteHost() { return graphiteHost; } public void setGraphite…

Jersey posting multipart data

This took me sometime to figure out mostly it was because I was only including jersey-multipart-1.6.jar but I was not including mimepull-1.3.jar.

So the intent is to upload a file using REST api and we need pass meta attributes in addition to uploading the file. Also the intent is to stream the file instead of first storing it on the local disk. Here is some sample code.
@Path("/upload-service") public class UploadService { @Context protected HttpServletResponse response; @Context protected HttpServletRequest request; @POST @Consumes(MediaType.MULTIPART_FORM_DATA) @Produces(MediaType.APPLICATION_JSON) public String uploadFile(@PathParam("fileName") final String fileName, @FormDataParam("workgroupId") String workgroupId, @FormDataParam("userId") final int userId, @FormDataParam("content") final InputStream content) throws JSONException { //.......Upload the file to S3 or netapp or any storage service } }
Now to tes…