I'm connecting the database of a legacy application to another database by using a CDC tool (I'm using Zendesk's Maxwell) to read data from the database, and another program I'm writing to write data into the database that originated elsewhere.
The problem is that when the foreign data is written into the legacy database, the CDC tool will pick it up. I want to prevent this, since that foreign data already exists in the other system.
I thought about adding a column to all the tables in the legacy database, called _origin for example, and putting the origin of each row in that column. The issue with that is that the legacy application does a lot of updates, so the CDC tool would miss real updates since, the _origin column wouldn't change.
Is there a way to somehow write metadata into the MySQL binlog to indicate the origin of this specific transaction? I would have to figure out how to read it using the CDC tool or modify a CDC tool to read such metadata, but I want to see if it's even possible.
Or, is there a better way to do this?
No, there's no way to write your own custom metadata into the binlog. Just the data itself, and certain session variables.
One solution could be when you read data from the CDC to insert into your destination database, use REPLACE instead of INSERT. The syntax is the same, but it overwrites instead of appends if the row already exists.
Related
I am doing research on MySQL data. I used the dbConnect function to connect to the database and used dbReadTable to read a table.
My question is: if I start cleaning data to make it tidy using tidyr and dplyr, etc, will this change the data from the database (data that is stored in mySQL and was collected by researcher)
Or does cleaning data in R only change the data called upon in R and have NO EFFECT ON THE database.
I need a definitive, well-backed, and professional answer as the data I'm dealing with is pretty important and valuable.
Given a database connection, you can definitely modify data in the database by using any of the keywords such as INSERT, UPDATE, DELETE depending on the role of the database user;
One safe way to avoid any modification of the database is ask the database administrator (I assume you are not the one) to create a user that has only read access to it, and then connect the database using this specific user. Then you would be safe to do analysis without unintentionally injecting anything into your database because the database won't allow you to do so;
But most importantly consult with the database administrator before taking next step, this answer is just for giving a clue on how to do this safely from my personal perspective. No responsibility taken for the next move you made.
I needed to insert some initial (default) data into a new database and I found this Inserts tab on MySQL Workbench EER Diagram table editing form
My assumption was that I can use it to insert initial (default) data that will get propagated to the database during synchronization (not sure how it will get merged with any existing data in the database though...). I added couple rows and synced model with an empty database, but no data was inserted.
So, my question is what this Inserts tab is for on the Table Editing screen?
I use MySQL Workbench 6.
P.S. If somebody can also point to an easy way to insert initial (default) data (except simply running a SQL script) I will appreciate it.
Thank you.
The data added on the INSERTs page is indeed thought to be like an initial set of (test)data. It doesn't consider existing data however. I think it is also only used if you do forward engineering, not on synchronization.
Other ways of inserting data always involve an SQL script, that's what the (text) API is about for SQL servers. But you can add scripts to your model too (see the overview page). They are not run automatically, however.
I am facing a problem for a task I have to do at work.
I have a MySQL database which holds the information of several clients of my company and I have to create a backup/restore procedure to backup and restore such information for any single client. To clarify, if my client A is losing his data, I have to be able to recover such data being sure I am not modifying the data of client B, C, ...
I am not a DB administrator, so I don't know if I can do this using standard mysql tools (such as mysqldump) or any other backup tools (such as Percona Xtrabackup).
To backup, my research (and my intuition) led my to this possibile solution:
create the restore insert statement using the insert-select syntax (http://dev.mysql.com/doc/refman/5.1/en/insert-select.html);
save this inserts into a sql file, either in proper order or allowing this script to temporarily disable the foreign key checks to meet foreign keys' constraint;
of course, I do this for all my clients on a daily base, using a file for each client (and day).
Then, in the case I have to restore the data for a specific client:
I delete all his data left;
I restore the correct data using his sql file I created during the backup.
This way I believe I may recover the right data of client A without touching the data of client B. Is my solution eventually working? Is there any better way to achieve the same result? Or do you need more information about my problem?
Please, forgive me if this question is not well-formed, but I am new here and this is my first question so I may be unprecise...thanks anyway for the help.
Note: we will also backup the entire database with mysqldump.
You can use the --where parameter, you could provide a condition like *client_id=N* . Of course I am making an assumption since you don't provide any information on your schema.
If you have a Star schema , then you could probably write a small script that backups all lookup tables (considering they are adequately small) by using this parameter --tables and use the --where condition for your client data table. For additional performance, perhaps you could partition the table by the client_id.
I am very new to this and a good friend is in a bind. I am at my wits end. I have used gui's like navicat and sqlyog to do this but, only manually.
His band info data (schedules and whatnot) is in a MYSQL database on a server (admin server).
I am putting together a basic site for him written in Perl that grabs data from a database that resides on my server (public server) and displays schedule info, previous gig newsletters and some fan interaction.
He uses an administrative interface, which he likes and desires to keep, to manage the data on the admin server.
The admin server db has a bunch of tables and even table data the public db does not need.
So, I created tables on the public side that only contain relevant data.
I basically used a gui to export the data, then insert to the public side whenever he made updates to the admin db (copy and paste).
(FYI I am using DBI module to access the data in/via my public db perl script.)
I could access the admin server directly to grab only the data I need but, the whole purpose of this is to "mirror" the data not access the admin server on every query. Also, some tables are THOUSANDS of rows and parsing every row in a loop seemed too "bulky" to me. There is however a "time" column which could be utilized to compare to.
I cannot "sync" due to the fact that the structures are different, I only need the relevant table data from only three tables.
SO...... I desire to automate!
I read "copy" was a fast way but, my findings in how to implement were too advanced for my level.
I do not have the luxury of placing a script on the admin server to notify when there was an update.
1- I would like to set up a script to check a table to see if a row was updated or added on the admin servers db.
I would then desire to update or insert the new or changed data to the public servers db.
This "check" could be set up in a cron job I guess or triggered when a specific page loads on the public side. (the same sub routine called by the cron I would assume).
This data does not need to be "real time" but, if he updates something it would be nice to have it appear as quickly as possible.
I have done much reading, module research and experimenting but, here I am again at stackoverflow where I always get great advice and examples.
Much of the terminology is still quite over my head so verbose examples with explanations really help me learn quicker.
Thanks in advance.
The two terms you are looking for are either "replication" or "ETL".
First, replication approach.
Let's assume your admin server has tables T1, T2, T3 and your public server has tables TP1, TP2.
So, what you want to do (since you have different table structres as you said) is:
Take the tables from public server, and create exact copies of those tables on the admin server (TP1 and TP2).
Create a trigger on the admin server's original tables to populate the data from T1/T2/T3 into admin server's copy of TP1/TP2.
You will also need to do initial data population from T1/T2/T3 into admin server's copy of TP1/TP2. Duh.
Set up the "replication" from admin server's TP1/TP2 to public server's TP1/TP2
A different approach is to write a program (such programs are called ETL - Extract-Transform-Load) which will extract the data from T1/T2/T3 on admin server (the "E" part of "ETL"), massage the data into format suitable for loading into TP1/TP2 tables (the "T" part of "ETL"), transfer (via ftp/scp/whatnot) those files to public server, and the second half of the program (the "L") part will load the files into the tables TP1/TP2 on public server. Both halfs of the program would be launched by cron or your scheduler of choice.
There's an article with a very good example of how to start building Perl/MySQL ETL: http://oreilly.com/pub/a/databases/2007/04/12/building-a-data-warehouse-with-mysql-and-perl.html?page=2
If you prefer not to build your own, here's a list of open source ETL systems, never used any of them so no opinions on their usability/quality: http://www.manageability.org/blog/stuff/open-source-etl
I think you've misunderstood ETL as a problem domain, which is complicated, versus ETL as a one-off solution, which is often not much harder than writing a report. Unless I've totally misunderstood your problem, you don't need a general ETL solution, you need a one-off solution that works on a handful of tables and a few thousand rows. ETL and Schema mapping sound scarier than they are for a single job. (The generalization, scaling, change-management, and OLTP-to-OLAP support of ETL are where it gets especially difficult.) If you can use Perl to write a report out of a SQL database, you probably know enough to handle the ETL involved here.
1- I would like to set up a script to check a table to see if a row was updated or added on the admin servers db. I would then desire to update or insert the new or changed data to the public servers db.
If every table you need to pull from has an update timestamp column, then your cron job includes some SELECT statements with WHERE clauses based on the last time the cron job ran to get only the updates. Tables without an update timestamp will probably need a full dump.
I'd use a one-to-one table mapping unless normalization was required... just simpler to my opinion. Why complicate it with "big" schema changes if you don't have to?
some tables are THOUSANDS of rows and parsing every row in a loop seemed too "bulky" to me.
Limit your queries to only the columns you need (and if there are no BLOBs or exceptionally big columns in what you need) a few thousand rows should not be a problem via DBI with a FETCHALL method. Loop all you want locally, just make as few trips to the remote database as possible.
If a row is has a newer date, update it. I will also have to check for new rows for insertion.
Each table needs one SELECT ... WHERE updated_timestamp_columnname > last_cron_run_timestamp. That result set will contain all rows with newer timestamps, which contains newly inserted rows (if the timestamp column behaves like I'd expect). For updating your local database, check out MySQL's ON DUPLICATE KEY UPDATE syntax... this will let you do it in one step.
... how to implement were too advanced for my level ...
Yes, I have actually done this already but, I have to manually update...
Some questions to help us understand your level... Are you hitting the database from the mysql client command-line or from a GUI? Have you gotten to the point where you've wrapped your SQL queries in Perl and DBI, yet?
If the two databases have different, you'll need an ETL solution to map from one schema to another.
If the schemas are the same, all you have to do is replicate the data from one to the other.
Why not just create identical structure on the 'slave' server to the master server. Then create a small table that keeps track of the last timestamp or id for the updated tables.
Then select from the master all rows changed since the last timestamp or greater than the id. Insert them into the matching table on the slave server.
You will need to be careful of updated rows. If a row on the master is updated but the timestamp doesn't change then how will you tell which rows to fetch? If that's not an issue the process is quite simple.
If it is an issue then you need to be more sophisticated, but without knowing the data structure and update mechanism its a goose chase to give pointers on it.
The script could be called by cron every so often to update the changes.
if the database structures must be different on the two servers then a simple translation step may need to be added, but most of the time that can be done within the sql select statement and maybe a join or two.
I need to convert data that already exists in a MySQL database, to a SQL Server database.
The caveat here is that the old database was poorly designed, but the new one is in a proper 3N form. Does any one have any tips on how to go about doing this? I have SSMS 2005.
Can I use this to connect to the MySQL DB and create a DTS? Or do I need to use SSIS?
Do I need to script out the MySQL DB and alter every statement to "insert" into the SQL Server DB?
Has anyone gone through this before? Please HELP!!!
See this link. The idea is to add your MySQL database as a linked server in SQL Server via the MySQL ODBC driver. Then you can perform any operations you like on the MySQL database via SSMS, including copying data into SQL Server.
Congrats on moving up in the RDBMS world!
SSIS is designed to do this kind of thing. The first step is to map out manually where each piece of data will go in the new structure. So your old table had four fields, in your new structure fileds1 and 2 go to table a and field three and four go to table b, but you also need to have the autogenerated id from table a. Make notes as to where data types have changed and you may need to make adjustments or where you have required fileds where the data was not required before etc.
What I usually do is create staging tables. Put the data in the denormalized form in one staging table and then move to normalized staging tables and do the clean up there and add the new ids as soon as you have them to the staging tables. One thing you will need to do if you are moving from a denormalized database to a normalized one is that you will need to eliminate the duplicates from the parent tables before inserting them into the actual production tables. You may also need to do dataclean up as there may be required fileds in the new structure that were not required in the old or data converstion issues becasue of moving to better datatypes (for instance if you stored dates in the old database in varchar fields but properly move to datetime in the new db, you may have some records which don't have valid dates.
ANother issue you need to think about is how you will convert from the old record ids to the new ones.
This is not a an easy task, but it is doable if you take your time and work methodically. Now is not the time to try shortcuts.
What you need is an ETL (extract, transform, load) tool.
http://en.wikipedia.org/wiki/Extract,_transform,_load#Tools
I don't really know how far an 'ETL' tool will get you depending on the original and new database designs. In my career I've had to do more than a few data migrations and we usually always had to design a special utility which would update a fresh database with records from the old database, and yes we coded it complete with all the update/insert statements that would transform data.
I don't know how many tables your database has, but if they are not too many then you could consider going the grunt root. That's one technique that's guaranteed to work after all.
If you go to your database in SSMS and right-click, under tasks should be an option for "Import Data". You can try to use that. It's basically just a wizard that creates an SSIS package for you, which it can then either run for you automatically or which you can save and then alter as needed.
The big issue is how you need to transform the data. This goes into a lot of specifics which you don't include (and which are probably too numerous for you to include here anyway).
I'm certain that SSIS can handle whatever transformations you need to do to change it from the old format to the new. An alternative though would be to just import the tables into MS SQL as-is into staging tables, then use SQL code to transform the data into the 3NF tables. It's all a matter of what your most comfortable with. If you go the second route, then the import process that I mentioned above in SSMS could be used. It will even create the destination tables for you. Just be sure that you give them unique names, maybe prefixing them with "STG_" or something.
Davud mentioned linked servers. That's definitely another way that you can go (and got my upvote). Personally, I prefer to copy the tables over into MS SQL first since linked servers can sometimes have weirdness, especially when it comes to data types not mapping between different providers. Having the tables all in MS SQL will also probably be a bit faster and saves time if you have to rerun or correct portions of the data. As I said though, the linked server method would probably be fine too.
I have done this going the other direction and SSIS works fine, although I might have needed to use a script task to deal with slight data type weirdness. SSIS does ETL.