What is the difference between cursor and bulk collect

Selecting from a table with a rownum where clause is a statement that does not have any business logic. But again: Check the code, rownum in a delete sounds just wrong! Actually venzi u dint get my Question. You are right! The different values come from existing, populated collections or host arrays. Actually I note that you have two unnecessary steps in there.

So you can remove those lines and it still works fine:. Others, like that one used in my example, do not have virtual limits, however, they do have physical. The collection is stored within the PGA of the session process which means that the bigger the collection gets the more memory is used by the session process. So the size of the collection is depending on the amount of the physical memory available on the database machine.

I have still confusion. Please clear. Yes, the query takes the time for fetching the results, that is correct. So for every row you primary have a soft parse, a round trip to the database and a query execution. I am calling a function through cursor , But i want to do in collection how? If you need to handle the logic differently based on values, depending on what that logic is, you may either be able to put the condition as part of the WHERE clause, create multiple collections and have multiple FORALL statements, or fall back to conventional DML operations with a loop.

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This site uses Akismet to reduce spam. Learn how your comment data is processed. Well, also all rows inserted?

Like this: Like Loading Author: Gerald Developer, Oracle expert, performance enthusiast and genuine technology geek. Hi srikanth, That was one of the major toughts on this blog! Raj Like Like. Regards, Gerald Like Like.

Hi Venzi, This very heplful. Thanks, Mike Like Like. No soft parses, reading of the new values of the binds… Regards, Gerald Like Like. Regards, James Like Like. Hi James, These tests were done on Gerald, There is a subtle flaw in your tests that leads to incorrect conclusions.

You are not alone in your conclusions. Thanks, Gerald Like Like. Hi Tony, Yes, they show the same performance with that optimizer level! Gerald, Perhaps we have done this to death but I am a little confused. Newsletters may contain advertising.

You can unsubscribe at any time. Will there be any increase in performance by using bulk insert instead of cursor for loop and insert?

I have read both bulk collect and cursor for loop are performance wise similar from 10g. Is that the same in bulk insert case also? Definitely there is increase in performance with bulk insert because of less number of context switches from PLSQL engine to SQL engine when compared to cursor for loop insert. The only motivation to use loop instead of bulk insert I can imagine to achieve greater control i. Instead of slowly looping through your data row by row, you can select into an array and then process that array.

The steps to do this are simple. Simply declare an array of records, select into it and then process the records. Here is an. I have had a lot of people express some confusion over how to get this working. Here is the same code using a cursor for fetching.

That will keep Oracle from selecting more than that number of records at a time. Why would you want to limit it? If you are processing 1 million rows, you want to work on chunks of data at a time.

Remember that more is not always better. Start with and test. Bump it up and test. For the records here is the quote from Tom Kyte "Are implicit cursor for loops optimized with an array fetch of ?

Yes" — Claude. Wernfried Domscheit Wernfried Domscheit Thanks for the general hints on performance. However, Pavel Smirnov provided the matching answer to my question: implicite cursors are internally optimized so there is no need to convert the implicite cursor to a manually optimized explicite one. Sign up or log in Sign up using Google. Sign up using Facebook. Sign up using Email and Password. Post as a guest Name. Email Required, but never shown. The Overflow Blog. Does ES6 make JavaScript frameworks obsolete?

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