I have a VERY large (50 million+ records) dataset that I am importing from an old Interbase database into a new SQL Server database.
My current approach is:
acquire csv files from the Interbase database (done, used a program called "FBExport" I found somewhere online)
The schema of the old database doesn't match the new one (not under my control), so now I need to mass edit certain fields in order for them to work in the new database. This is the area I need help with
after editing to the correct schema, I am using SqlBulkCopy to copy the newly edited data set into the SQL Server database.
Part 3 works very quickly, diagnostics shows that importing 10,000 records at once is done almost instantly.
My current (slow) approach to part 2 is I just read the csv file line by line, and lookup the relevant information (ex. the csv file has an ID that is XXX########, whereas the new database has a separate column for each XXX and ########. ex2. the csv file references a model via a string, but the new database references via an ID in the model table) and then insert a new row into my local table, and then SqlBulkCopy after my local table gets large.
My question is: What would be the "best" approach (perfomance wise) for this data-editing step? I figure there is very likely a linq-type approach to this, would that perform better, and how would I go about doing that if it would?
If step #3’s importing is very quick, I would be tempted to create a temporary database whose schema exactly matches the old database and import the records into it. Then I’d look at adding additional columns to the temporary table where you need to split the XXX######## into XXX and ########. You could then use SQL to split the source column into the two separate ones. You could likewise use SQL to do whatever ID based lookups and updates you need to ensure the record relationships continue to be correct.
Once the data has been massaged into a format which is acceptable, you can insert the records into the final tables using IDENTITY_INSERT ON, excluding all legacy columns/information.
In my mind, the primary advantage of doing it within the temporary SQL DB is that at any time you can write queries to ensure that record relationships using the old key(s) are still correctly related to records using the new database’s auto generated keys.
This is of coursed based on me being more comfortable doing data transformations/validation in SQL than in C#.
Related
I'm migrating data from one system to another and will be receiving a CSV file with the data to import. The file could contain up to a million records to import. I need to get each line in the file, validate it and put the data into the relevant tables. For example, the CSV would be like:
Mr,Bob,Smith,1 high street,London,ec1,012345789,work(this needs to be looked up in another table to get the ID)
There's a lot more data than this example in the real files.
So, the SQL would be something like this:
Declare #UserID
Insert into User
Values ('Mr', 'Bob', 'Smith', 0123456789)
Set #UserID = ##Identity
Insert into Address
Values ('1 high street', 'London', 'ec1', select ID from AddressType where AddressTypeName = 'work')
I was thinking of iterating over each row and call an SP with the parameters from the file which will contain the SQL above. Would this be the best way of tackling this? It's not time critical as this will just be run once when updating a site.
I'm using C# and SQL Server 2008 R2.
What about you load it into a temporary table (note that this may be logically temporary - not necessarily technically) as staging, then process it from there. This is standard ETL behavior (and a million is tiny for ETL), you first stage the data, then clean it, then put it to the final place.
When performing tasks of this nature, you do not think in terms of rotating through each record individually as that will be a huge performence problem. In this case you bulk insert the records to a staging table or use the wizard to import to a staging table (look out for teh deafult 50 characters espcially in the address field).Then you write set-based code to do any clean up you need (removing bad telephone numbers or zip code or email addresses or states or records missing data in fields that are required in your database or transforing data using lookup tables (suppose you have table with certain required values, those are likely not the same values that you wil find in this file, you need to convert them. We use doctor specialties a lot. So our system might store them as GP but the file might give us a value of General Practioner. You need to look at all teh non-matching values for the field and then determine if you can map them to existing values, if you need to throw the record out or if you need to add more values to your lookup table. Once you have gotten rid of records you don't want and cleaned up those you can in your staging table then you import to the prod tables. Inserts should be written using the SELECT version of INSERT not with the VALUES clause when you are writing more than one or two records.
I am writing an internal application and one of the functions will be importing data from a remote system. The data from the remote system comes over as a CSV file. I need to compare the data in my system with that of the CSV file.
I need to apply any changes to my system (Adds and Changes). I need to track each field that is changed.
My database is normalized so I'm dealing with about 10 tables to correspond with the data in the CSV file. What is the best way to implement this? Each CSV file has about 500,000 records that are processed daily. I started by querying row by row from my SQL database using a lookup ID then using c# do do a field by field compare and updating or inserting as necessary; however, this takes way too long.
Any suggestions?
You can do following:
Load cvs file into staging table in your db;
Perform validation and clean-up routines on it (if necessary)
Perform your comparisons and updates on your live data
Wipe out all data from staging table
Using that approach you can implement almost all clean-up, validation, and update logic using your RDBMS functionality.
If your RDBMS is SQL Server you can leverage SQL Server Integration Services.
If you have anything that serves as a unique key, you can do the following:
Create a new table Hashes that contains a unique key and a hash of all fields associated with that key (do not use .NET's object.GetHashCode(), as the value returned does change from time to time by design. I personally use Google's CityHash which I ported to C#).
When you get a new CSV file, compute the hash value for each key
Check the Hashes table for each row in the CSV file.
If there is no entry for the unique key, create one and insert the row.
If there is an entry, see if the hash has changed.
If it has, update the hash in the Hashes table and update data.
Expanding on the first comment to your question.
Create an appropriately indexed table that matches the format of your csv file and dump the data straight into it.
Have a stored procedure with appropriate queries to update/delete/insert to the active tables.
Get rid of the temporary table.
I am trying to design a window based application in C#.NET. I am reading csv file in data grid view and then insert those data into database. I am using SqlBulkCopy to insert data from csv file into database. My concern is, when I am trying to insert data into database (which already consist data) I am getting error of primary key constraint. I want to know whether it is possible to compare value before inserting into database using SqlBulkCopy. If value exist in database it should do update.
Can anyone provide me logic for this.
Thanks.
If you really, really know that the dupes aren't needed, just set the "Ignore Dupes" option on the index for the PK and you're done.
You need to read the data from the database into a list first.
Then when you load the csv you discard any duplicates.
Also, when you insert you should possibly ignore the primary key and let the sql database generate the key.
There's no way to do any logic when you're firehosing data in via SQLBulkCopy. Even triggers (shudder) are turned off.
What you should do is bulkcopy your data into an empty staging table, then run a stored procedure that merges the data from the staging table into the real, non-empty table.
If you're using SQL 2008, then you can use the MERGE command, otherwise you'll just have to code around it with a separate update and insert.
I have a folder that contains more than 100 .txt files. These files contain huge amount of data that needs to be orchestrated and updated in the SQL Server table. Each text file line will have only two columns that interests me and based upon the 1st column data (which is a PK in the SQL Server Table) I want to update the 2nd column data in the DB table.
Please suggest the best way to do it in C# 3.0
Presently I am using a StringBuilder and appending the Update query.
I think first you should use Bulk Copy to import the data to the sql server and then you write stored procedure. Building the query and then running will make the whole process slow.
I'm building an application to import data into a sql server 2008 Express db.
This database is being used by an application that is currently in production.
The data that needs to be imported comes from various sources, mostly excel sheets and xml files.
The database has the following tables:
tools
powertools
strikingtools
owners
Each row, or xml tag in the source files has information about 1 tool:
name, tooltype, weight, wattage, owner, material, etc...
Each of these rows has the name of the tool's owner this name has to be inserted into the owners table but only if the name isn't already in there.
For each of these rows a new row needs to be inserted in the tools table.
The tools table has a field owner_id with a foreign key to the owners table where the primary key of the corresponding row in the owners table needs to be set
Depending on the tooltype a new row must be created in either the powertools table or the strikingtools table. These 2 tables also have a tool_id field with a foreign key to the tools table that must be filled in.
The tools table has a tool_owner_id field with a foreign key to the owners table that must be filled in.
If any of the rows in the importfile fails to import for some reason, the entire import needs to be rolled back
Currently I'm using a dataset to do this but for some large files (over 200.000 tools) this requires quite a lot of memory. Can anybody think of a better aproach for this?
There are two main issues to be solved:
Parsing the a large XML document efficiently.
Adding a large amount of records to the database.
XML Parsing
Although the DataSet approach works, the whole XML document is loaded into memory. To improve the efficiency of working with large XML documents you might want look at the XmlReader class. The API is slightly more difficult to use than what DataSet provides. But you will get the benefit of not loading the whole DOM into memory at once.
Inserting records to the DB
To satisfy your Atomicity requirement you can use a single database transaction but the large number of records you are dealing with for a single transaction is not ideal. You will most likely incur issues like:
Database having to deal with a large number of locks
Database locks that might escalate from row locks to page locks and even table locks.
Concurrent use of the database will be severely affect during the import.
I would recommend the following instead of a single DB transaction:
See if it possible to create smaller transaction batches. Maybe 100 records at a time. Perhaps it is possible to logically load sections of the XML file together, where it would be acceptable load a subset of the data as a unit into the system.
Validate as much of your data upfront. E.g. Check that required fields are filled or that FK's are correct.
Make the upload repeatable. Skip over existing data.
Provide a manual undo strategy. I know this is easier said than done, but might even be required as an additional business rule. For example the upload was successful but someone realises a couple of hours later that the wrong file was uploaded.
It might be useful to upload your data to a initial staging area in your DB to perform validations and to mark which records have been processed.
Use SSIS, and create and ETL package.
Use Transactions for the roll back feature, and stored procedure that handle creating/checking the foreign keys.