I need to query a hp vertica database from SQL Server stored procedure. It is a join query and If I use linked server, it is going to fire as 2 separate selects and join it in the SQL Server . Is there any way I can use ODBC to fire the join query to Vertica from TSQL and get the processed result set back into an SQL table.?
Any other approach to suggest to achieve this ?
You may need to use OPENQUERY syntax in SQL Server, to get the full query sent to Vertica for execution there... There are other possibilities, but we'd need much more detail about what you have in play (especially but not only your current query) to usefully discuss them.
Related
Here's the basic idea of what I want to do in SSIS:
I have a large query against a production Oracle database, and I need the following where clause that brings in a long list of ids from SQL Server. From there, the results are sent elsewhere.
select ...
from Oracle_table(s) --multi-join
where id in ([select distinct id from SQL_SERVER_table])
Alternatively, I could write the query this way:
select ...
from Oracle_table(s) --multi-join
...
join SQL_SERVER_table sst on sst.ID = Oracle_table.ID
Here are my limitations:
The Oracle query is large and cannot be run without the where id in (... clause
This means I cannot run the Oracle query, then join it against the ids in another step. I tried this, and the DBA's killed the temp table after it became 3 TB in size.
I have 160k id's
This means it is not practical to iterate through the id's one by one. In the past, I have run against ~1000 IDs, using a comma-separated list. It runs relatively fast - a few minutes.
The main query is in Oracle, but the ids are in SQL Server
I do not have the ability to write to Oracle
I've found many questions like this.
None of the answers I have found have a solution to my limitations.
Similar question:
Query a database based on result of query from another database
To prevent loading all rows from the Oracle table. The only way is to apply the filter in the Oracle database engine. I don't think this can be achieved using SSIS since you have more than 160000 ids in the SQL Server table, which cannot be efficiently loaded and passed to the Oracle SQL command:
Using Lookups and Merge Join will require loading all data from the Oracle database
Retrieving data from SQL Server, building a comma-separated string, and passing it to the Oracle SQL command cannot be done with too many IDs (160K).
The same issue using a Script Task.
Creating a Linked Server in SQL Server and Joining both tables will load all data from the Oracle database.
To solve your problem, you should search for a way to create a link to the SQL Server database from the Oracle engine.
Oracle Heterogenous Services
I don't have much experience in Oracle databases. Still, after a small research, I found something in Oracle equivalent to "Linked Servers" in SQL Server called "heterogeneous connectivity".
The query syntax should look like this:
select *
from Oracle_table
where id in (select distinct id from SQL_SERVER_table#sqlserverdsn)
You can refer to the following step-by-step guides to read more on how to connect to SQL Server tables from Oracle:
What is Oracle equivalent for Linked Server and can you join with SQL Server?
Making a Connection from Oracle to SQL Server - 1
Making a Connection from Oracle to SQL Server - 2
Heterogeneous Database connections - Oracle to SQL Server
Importing Data from SQL Server to a staging table in Oracle
Another approach is to use a Data Flow Task that imports IDs from SQL Server to a staging table in Oracle. Then use the staging table in your Oracle query. It would be better to create an index on the staging table. (If you do not have permission to write to the Oracle database, try to get permission to a separate staging database.)
Example of exporting data from SQL Server to Oracle:
Export SQL Server Data to Oracle using SSIS
Minimizing the data load from the Oracle table
If none of the solutions above solves your issue. You can try minimizing the data loaded from the Oracle database as much as possible.
As an example, you can try to get the Minimum and Maximum IDs from the SQL Server table, store both values within two variables. Then, you can use both variables in the SQL Command that loads the data from the Oracle table, like the following:
SELECT * FROM Oracle_Table WHERE ID > #MinID and ID < #MaxID
This will remove a bunch of useless data in your operation. In case your ID column is a string, you can use other measures to filter data, such as the string length, the first character.
I am trying to insert rows into a Microsoft SQL Server 2014 table from a query that hits a linked Oracle 11g server. I have read only access rights on the linked server. I have traditionally used OPENQUERY to to do something like the following:
INSERT INTO <TABLE> SELECT * FROM OPENQUERY(LINKED_SERVER, <SQL>)
Over time the SQL queries I run have been getting progressively more complex and recently surpassed the OPENQUERY limit of 8000 characters. The general consensus on the web appears to be to switch to something like the following:
INSERT INTO <TABLE> EXECUTE(<SQL>) AT LINKED_SERVER
However, this seems to require that distributed transactions are enabled on the linked server, which isn't an option this project. Are there any other possible solutions I am missing?
Can you get your second method to work if you disable the "remote proc transaction promotion" linked server option?
EXEC master.dbo.sp_serveroption
#server = 'YourLinkedServerName',
#optname = 'remote proc transaction promotion',
#optvalue = 'false'
If SQL Server Integration Services is installed/available, you could do this with an SSIS package. SQL Server Import/Export Wizard can automate a lot of the package configuration/setup for you.
Here's a previous question with some useful links on SSIS to Oracle:
Connecting to Oracle Database using Sql Server Integration Services
If you're interested in running it via T-SQL, here's an article on executing SSIS packages from a stored proc:
http://www.databasejournal.com/features/mssql/executing-a-ssis-package-from-stored-procedure-in-sql-server.html
I've been in a similar situation before, what worked for me was to decompose the large query string while still using the query method below. (I did not have the luxury of SSIS).
FROM OPENQUERY(LINKED_SERVER, < SQL >)
Instead of Inserting directly into your table, move your main result set into a local temporary landing table first (could be a physical or temp table).
Decompose your < SQL > query by moving transformation and business logic code into SQL Server boundary out of the < SQL > query.
If you have joins in your < SQL > query bring these result sets across to SQL Server as well and then join locally to your main result set.
Finally perform your insert locally.
Clear your staging area.
There are various approaches (like wrapping your open queries in Views) but I like flexibility and found that reducing the size of my open queries to the minimum, storing and transforming locally yielded better results.
Hope this helps.
I am currently reviewing some jobs that run stored procedures on a database. All of these stored procedures are connecting to a linked server(s). I am not too familiar with this functionality. I am at the moment attempting to determine why these were used versus just a normal query as the queries I am running seem to be pulling in the data.
I read this, which is MSDNs explanation of openquery. :
http://technet.microsoft.com/en-us/library/ms188427.aspx
I also read this, which is a stackoverflow link talking about why not to use it on local server. :
Why is using OPENQUERY on a local server bad?
My question is do you basically just use this when the stored procedure requires the embedded credentials of the linked server? Or are there more reasons for using OpenQuery that I am not aware of?
Two advantages I can think of using openquery. It can reduce the amount of data you'd need to transfer by doing the necessary filtering on the remote server. It can allow the query optimizer on the remote server to choose the optimal execution plan when joining tables.
The other alternative is using REMOTE JOIN
I've had some luck using it but Aaron Bertrand has a nice write up about it here.. http://www.mssqltips.com/sqlservertip/2765/revisit-your-use-of-the-sql-server-remote-join-hint/
Here is the MS documentation
REMOTE
Specifies that the join operation is performed on the site of the right table. This is useful when the left table is a local table and the right table is a remote table. REMOTE should be used only when the left table has fewer rows than the right table.
If the right table is local, the join is performed locally. If both tables are remote but from different data sources, REMOTE causes the join to be performed on the site of the right table. If both tables are remote tables from the same data source, REMOTE is not required.
REMOTE cannot be used when one of the values being compared in the join predicate is cast to a different collation using the COLLATE clause.
REMOTE can be used only for INNER JOIN operations.
I was told by our IT team that we cannot use the Openquery command in MS Sql Server anymore. They claimed it was possible to slow down the server because every query requires a full table load, and all queries slow it down, etc.etc.
I was somewhat puzzled by this as I thought an OpenQuery command was similar to the 'passthrough' query in Access. The query goes to the IBM server, which executes the command and only sends the results back to SQL Server. I have read through OpenQuery on the internet and nothing I've read makes me believe that it loads or sends a whole table and then SQL Server filters the results.
I assume its possible for them to lock down the DB2 servers and prevent linked servers from SQL Server, but for my future knowledge can someone explain any perils to using OpenQuery when connecting to IBM DB2?
Thanks,
Please read this. Can you avoid OpenQuery? The best alternative would be to use a store procedure command or at least craft a EXECSQL with a SP target.
How can we get information regarding poorly performing sqls(taking too much time for execution)
Does MS SQL server maintains tables/views (Similar to v$sql in Oracle) for storing sql queries.
I Use the SQL Profiler to collect statistic data wich I then can use to nail down where there are need to do some work, tweak indexes and so on.
Here are some tips about monitoring with Profiler:
http://www.developer.com/db/article.php/3490086
http://vyaskn.tripod.com/analyzing_profiler_output.htm
take a look at sys.dm_exec_query_stats and this page. SQL Server 2005+ only.