I recently switch to a new hosting provider for my application. My employees used the old site until the new site went live, however, the database backup from the old site was taken two days before the new site went live. So in the midst of transferring, records were being entered into the old site database while the new site had no existence of them (hence my two day time lag). How do I merge the two databases to reflect the changes?
A couple of things to note are the primary keys might be duplicated for some tables and there are only timestamps on a few tables as well. I would do a 'diff' or something of the sort, but the tables are dumped in different formats.
Any thoughts?
This is something where you'll need to actually understand your database schema. You'll need to create a program that can look at both versions of the database, identify which records are shared, which are not, and which have conflicting primary keys (vs ones which were updated with the same keys). It then needs to copy over changes, possibly replacing the value of primary keys (including the values in other rows that refer to the row being renumbered!) This isn't easy, and it's not an exact science - you'll be writing heuristics, and expect to do some manual repairs as well.
Next time shut that database down when you grab the final backup :)
You don't need to create any additional programs. All what you need, to setup replications from the old DB to the new one.
All your data from the old DB will automatically transfer to the new DB. At this period you should use you old DB as the main data source. And as soon as all data will be copied to the new location, you'll need just brake replica connection and change the DB address in your code (or DNS pointer) to the new one.
1. oldDB ===> replication ==> newDB
R/W operations
2. oldDB ==/= brake ==/= newDB
R/W operations
MySQL Doc: 15.1.1. How to Set Up Replication
Related
I'm writing the back-end for a web app in Spring and it uses a MySQL database on an AWS RDS instance to keep track of user data. Right now the SQL tables are separated by user groups (just a value in a column), so different groups have different access to data. Whenever a person using the app does a certain operation, we want to back up their part of the database, which can be viewed later, or replace their data in the current branch if they want.
The only way I can figure out how to do this is to create separate copies of every table for each backup and keep another table to keep track of what all the names of the tables are. This feels very inelegant and labor intensive.
So far all operations I do on the database are SQL queries from the server, and I would like to stay consistent with that.
Is there a nice way to do what I need?
Why would you want a separate table for each backup? You could have a single table that mirrored the main table but had a few additional fields to record some metadata about the change, for example the person making it, a timestamp, and the type of change either update or delete. Whenever a change is made, simply copy the old value over to this table and you will then have a complete history of the state of the record over time. You can still enforce the group-based access by keeping that column.
As for doing all this with queries, you will need some for viewing or restoring these archived changes, but the simplest way for maintaining the archived records is surely to create TRIGGERS on the main tables. If you add BEFORE UPDATE and BEFORE DELETE TRIGGERS these can copy the old version of each record over to the archive (and also add the metadata at the same time) each time a record is updated or deleted.
I have software that reads only one database by name. However, every day I have to check for records that are 30+ days old so my solution is to rename the database everyday (appending a timestamp) and create a new one with the old name so my software can continue to run.
I need my software to read all of the databases but it can only read one. Is there a way to link the main database with the archived ones without copying the database? I don't think I can use MERGE because I won't be able to split the databases by day.
e.g.
Software only reads database MAINDB
Everyday, a cronjob renames the database. MAINDB becomes BKDB_2015_12_04. I can still access the database from mysql because it's not a dumped database.
A new MAINDB is made for the software to read.
However, I need the software to read the data stored in BKDB_2015_12_04 and any other database BKDP_*
I'd like to have the software, when reading MAINDB, also read BKDB_*
Essentially, I'm having some databases 'read-only' and I'm partitioning the data by day. I'm reading about using PARTITION but I'm dealing with an immense amount of data and I'm not sure if PARTITION is effective in dealing with this amount of data.
Renaming and re-creating a database is a "bad idea". How can you ever be sure that your database is not being accessed when you rename and re-create?
For example, say I'm in the middle of a purchase and my basket is written to a database table as I add items to it (unlikely scenario but possible). I'm browsing around choosing more items. In the time I'm browsing, the existing database is renamed and a new one re-created. Instantly, my basket is empty with no explanation.
With backups, what happens if your database is renamed half=way through a backup? How can you be sure that all your other renamed databases are backed up?
One final thing - what happens in the long run with renamed databases? Are they left there for ever? Are the dropped after a certain amount of time? etc
If you're checking for records that are 30+ days old, the only solution you should be considering is to time-stamp each record. If your tables are linked via single "master" table, put the time-stamp in there. Your queries can stay largely the same (except from adding a check for a times-stamp) and you don't have to calculate database names for the past 30 days
You should be able to do queries on all databases with UNION, all you need to know is the names of the databases:
select * from MAINDB.table_name
union all
select * from BKDB_2015_12_04.table_name
union all
select * from database_name.table_name
EDIT: To clarify throughout this post: when I say "schema" I am referring to "data-model," which are synonyms in my head. :)
My question is very similar to this question (Rails: Multiple databases, same schema), but mine is related to MySQL.
To reiterate the problem: I am developing a SAAS. The user will be given an option of which DB to connect to at startup. Most customers will be given two DBs: a production DB and a test DB, which means that every customer of mine will have 1-2 databases. So, if I have 10 clients, I will have about 20 databases to maintain. This is going to be difficult whenever the program (and datamodel) needs to be updated.
My question is: is there a way to have ONE datamodel for MULTIPLE databases? The accepted answer to the question I posted above is to combine everything into one database and use a company_id to separate out the data, but this has several foreseeable problems:
What happens when these transaction-based tables become inundated? My 1 customer right now has recorded 16k transactions already in the past month.
I'd have to add where company_id = to hundreds of SQL queries/updates/inserts (yes, Jeff Atwood, they're Parametrized SQL calls), which would have a severe impact on performance I can only assume.
Some tables store metadata, i.e., drop-down menu items that will be company-specific in some cases and application-universal in others. where company_id = would add an unfortunate layer of complexity.
It seems logical to me to create (a) new database(s) for each new customer and point their software client to their database(s). But, this will be a headache to maintain, so I'm looking to reduce this potential headache.
Create scripts for deployments for change to the DB schema, keep an in house database of all customers and keep that updated, write that in your scripts to pull from for the connection string.
Way better than trying to maintain a single database for all customers if your software package takes off.
FYI: I am currently with an organization that has ~4000 clients, all running separate instances of the same database (very similar, depending on the patch version they are on, etc) running the same software package. A lot of the customers are running upwards of 20-25k transactions per second.
A "database" in MySQL is called a "schema" by all the other database vendors. There are not separate databases in MySQL, just schemas.
FYI: (real) databases cannot have foreign keys between them, whereas schemas can.
Your test and production databases should most definitely not be on the same machine.
Use Tenant Per Schema, that way you don't have company_ids in every table.
Your database schema should either be generated by your ORM or it should be in source control in sql files, and you should have a script that automatically builds/patches the db. It is trivial to change this script so that it builds a schema per tenant.
I need to synch development mysql db with the production one.
Production db gets updated by user clicks and other data generated via web.
Development db gets updated with processing data.
What's the best practice to accomplish this?
I found some diff tools (eg. mySQL diff), but they don't manage updated records.
I also found some application solution: http://www.isocra.com/2004/10/dumptosql/
but I'm not sure it's a good practice as in this case I need to retest my code each time I add new innodb related tables.
Any ideas?
Take a look at mysqldump. It may serve you well enough for this.
Assuming your tables are all indexed with some sort of unique key you could do a dump and have it leave out the 'drop/create table' bits. Have it run as 'insert ignore' and you'll get the new data without effecting the existing data.
Another option would be to use the query part of mysqldump to dump only the new records from the production side. Again - have mysqldump leave off the 'drop/create' bits.
I am using Microsoft SQL Server 2008 R2.I have copied database A(myproduction database) to database B(Myreportin database) by creating SSIS package.Both databases are in same server.I want to run a job so that If any change(data modifications like inserting new rows or updating values of any row in any table) take place in database A that will also take place in my B database and sql job will run and acomplish the changing automatically.I don't want that in database B table will be dropped and recreated (as its not our business rule )instead only the change will take place.
Can any one help me please.Thanks in Advance.
I would suggest that you investigate using replication. Specifically, transactional replication if you need constant updates. Here's a bit from MSDN:
Transactional replication typically starts with a snapshot of the publication database objects and data. As soon as the initial snapshot is taken, subsequent data changes and schema modifications made at the Publisher are usually delivered to the Subscriber as they occur (in near real time). The data changes are applied to the Subscriber in the same order and within the same transaction boundaries as they occurred at the Publisher; therefore, within a publication, transactional consistency is guaranteed.
If you don't need constant updating (that comes at a price in performance, of course), you can consider the alternatives of merge replication or snapshot replication. Here's a page to start examining those alternatives.