Search Postgresql Archives

Re: Last inserted row id with complex PK

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

 






On Wed, Jan 8, 2014 at 10:22 AM, Tom Lane <tgl@xxxxxxxxxxxxx> wrote:
Francisco Olarte <folarte@xxxxxxxxxxxxxx> writes:
> Hi Nelson:
> On Wed, Jan 8, 2014 at 4:54 PM, Nelson Green <nelsongreen84@xxxxxxxxx> wrote:
>> I have a projects log table with a three column PK, project_num, person_num,
>> and sequence, where each new entry for a project/person combination
>> increments the sequence, which is not an auto incrementing sequence. Is
>> there any way to retrieve the last entry to the table? For instance, if the
>> last entry for person 427 on project 15 was sequence number 125, is that
>> information available to me anywhere?

> SELECT MAX(sequence) FROM project_log_table WHERE person_num=427 AND
> project_num=15

Note that this will not work terribly well if there are concurrent
insertions for the same person/project.  If that's not an issue, though,
it should be fine.  It may be OK even if there are sometimes concurrent
insertions, if you are prepared to retry duplicate-key failures.

Concurrency is not likely to be an issue for this system, but I would certainly plan for it since I can not rule it out.
 

> If it's a PK it should have an index and I believe it will be quite fast.

It will be fast as long as sequence is the low-order column in the index.

                        regards, tom lane


[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
[Index of Archives]     [Postgresql Jobs]     [Postgresql Admin]     [Postgresql Performance]     [Linux Clusters]     [PHP Home]     [PHP on Windows]     [Kernel Newbies]     [PHP Classes]     [PHP Books]     [PHP Databases]     [Postgresql & PHP]     [Yosemite]
  Powered by Linux