Re: shmem_seq may be a bad idea

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: Thomas Lockhart <lockhart(at)alumni(dot)caltech(dot)edu>
Cc: Peter Eisentraut <peter_e(at)gmx(dot)net>, pgsql-hackers(at)postgreSQL(dot)org, Michael Blakeley <mike(at)blakeley(dot)com>
Subject: Re: shmem_seq may be a bad idea
Date: 2000-05-02 15:52:33
Message-ID: 4046.957282753@sss.pgh.pa.us
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Thomas Lockhart <lockhart(at)alumni(dot)caltech(dot)edu> writes:
>> A while ago while thinking about a way to make ipcclean better I thunk
>> that perhaps the postmaster should write the keys of the segments it gets
>> to a flat-text file.

> Hmm. Could we write this to a separate shared memory segment? Much
> more likely to be of fixed length and compatible between versions, and
> more likely to exist or not exist with the same behavior as the large
> shared memory segment under discussion??

What happens if you get a key collision with some other application
for that segment? Seems to me that using shmem to remember where you
put your shmem segments is dangerously circular ;-)

The flat text file is not a bad idea, but I think the logic I suggested
yesterday makes it unnecessary...

regards, tom lane

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