Hello, David, thanks for your quick response. Usually it's one thread "per" in-memory table. Tables can be updated at random times and their random rows may be updated, some rows deleted or new rows inserted. In some other configuration, to avoid deletions, updates and inserts, the in-memory table is truncated and then all the records (the new "state" of the source data) are inserted into it.
The thread which runs SQL against all those tables frequently may do a scan of the whole table. -----Original Message----- From: David Zanter [mailto:dzan...@gmail.com] Sent: Friday, June 01, 2012 3:46 PM To: Derby Discussion Subject: Re: Derby Locks - best practices Do mean the scenario of: Multiple threads are updating the exact same rows or Multiple threads doing updates to different rows, but due to queries/indexes/etc are causing contention between each other. On Fri, Jun 1, 2012 at 3:16 PM, Pavel Bortnovskiy <pbortnovs...@jefferies.com> wrote: > Hello, all: > > > > Derby is used in my application in the in-memory only mode. For a long > time Derby's lock logic caused no worries, but recently some use cases > failed with lock timeouts. Thus I'm looking for guidance on best > practices for handling locks in Derby. A use-case which may cause > timeouts to obtain a > lock: one thread is executing an SQL statement which accesses two (or > more) in-memory tables. Those two tables are being modified by other > threads at random times. So, situations in which the SQL is executed > for a long time and the other threads are frequently updating the > tables may cause lock timeouts. > > > > Besides best practices to avoid timeouts and deadlocks, I would like > to ask the following questions: > > 1) What's the default length of lock timeouts? > > 2) Does my app need another layer of synchronization > mechanism/locks to avoid attempts to update in-memory tables or execute SQLs > against them? > > 3) Can my application utilize Derby's locks through some API - to > query their state or to use them in making a decision of whether to > batch updates or to execute them, to wait or execute the SQLs? > > > > Your help would be greatly appreciated, > > > > Pavel. > > Jefferies archives and monitors outgoing and incoming e-mail. The > contents of this email, including any attachments, are confidential to > the ordinary user of the email address to which it was addressed. If > you are not the addressee of this email you may not copy, forward, > disclose or otherwise use it or any part of it in any form whatsoever. > This email may be produced at the request of regulators or in > connection with civil litigation. Jefferies accepts no liability for > any errors or omissions arising as a result of transmission. Use by > other than intended recipients is prohibited. In the United Kingdom, > Jefferies operates as Jefferies International Limited; registered in > England: no. 1978621; registered office: Vintners Place, 68 Upper > Thames Street, London EC4V 3BJ. Jefferies International Limited is authorised > and regulated by the Financial Services Authority. Jefferies archives and monitors outgoing and incoming e-mail. The contents of this email, including any attachments, are confidential to the ordinary user of the email address to which it was addressed. If you are not the addressee of this email you may not copy, forward, disclose or otherwise use it or any part of it in any form whatsoever. This email may be produced at the request of regulators or in connection with civil litigation. Jefferies accepts no liability for any errors or omissions arising as a result of transmission. Use by other than intended recipients is prohibited. In the United Kingdom, Jefferies operates as Jefferies International Limited; registered in England: no. 1978621; registered office: Vintners Place, 68 Upper Thames Street, London EC4V 3BJ. Jefferies International Limited is authorised and regulated by the Financial Services Authority.
