Java JDBC - Oracle11g Sys Ref Cursor Vs pl/sql collectionsAsk Question

问题:

I would like to ask the experts of what is the recommendation for fetching 3000-5000 records from oracle 11g database from Java application (using JDBC). Our standard is to always invoke a stored procedure.

I did some research and found that ref cursor makes multiple round trips to the database based on the JDBC fetch count property. (can somebody throw more light on this of the end to end flow of how data is stored in memory in oracle and JVM when processing ref cursors)

I was thinking collections are more efficient because the data is sent in one shot to the caller (Java) from oracle db (use bulk collect). With this approach we can avoid multiple network calls from Java to Oracle servers. is this a true assumption?

Appreciate your help!

回答1:


This is a much bigger topic than anyone is willing to commit to in a posting. Here's a link that discusses how Oracle manages read consistency. That entire page is probably a good read to get some of idea of what's going on in the server. There's also an article here that discusses what happens using collections. How would you return the collection to a JDBC Client (not something I've ever tried)?

Essentially, there's a lot involved in performance, from how your database is configured to how your network is tuned to disk performance, to client performance, etc.

The short answer is you need to try things. Retrieving 3-5k records isn't a lot, and it depends on how big the record is, that your bringing back across the network. If they are 20 byte records, and your network (MTU?) size is 4k blocks, you can fit about 200 records in a block. At some point, you run into the law of diminishing returns.

I use stored procedures as a matter of habit, but you don't need to. It would depend on the complexity of the query (number of tables and the type of joins) and the ability for someone like a DBA to be able to go in and see what the query is doing.

Worrying about network trips is a little less critical, because there's only so much data you can stuff in a packet. There's going to be a number of network trips no matter what you use, it really depends on your use case to determine how critical it is to get that to a bare minimum.

标签: jdbc collections oracle11g sys-refcursor
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