From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
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To: | Robert Haas <robertmhaas(at)gmail(dot)com> |
Cc: | 5bih4k+4jfl6m39j23k(at)guerrillamail(dot)com, "pgsql-hackers(at)postgresql(dot)org" <pgsql-hackers(at)postgresql(dot)org> |
Subject: | Re: Parallel safety of CURRENT_* family |
Date: | 2016-12-01 21:27:01 |
Message-ID: | 14911.1480627621@sss.pgh.pa.us |
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Lists: | pgsql-hackers |
Robert Haas <robertmhaas(at)gmail(dot)com> writes:
> On Thu, Dec 1, 2016 at 3:46 PM, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
>> but it doesn't:
>>
>> regression=# select distinct transaction_timestamp() from tenk1;
>> transaction_timestamp
>> -------------------------------
>> 2016-12-01 15:44:12.839417-05
>> (1 row)
>>
>> How is that happening?
> Because the table is so small, the leader probably finishes running
> the whole plan before the workers finish starting up.
Good try, but EXPLAIN ANALYZE says that the workers are processing
some of the rows. Also, I see the same behavior with a much larger
test table.
> You can see the problem like this, though:
Yeah, I didn't have any doubt that it was real. Still don't know
why my test case isn't doing what I expected, though.
regards, tom lane
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