On 05/06/2017 04:57 PM, David Rowley wrote:
Andres mentioned in [2] that it might be worth exploring using atomics
to do the same job. So I went ahead and did that, and came up with the
attached, which is a slight variation on what he mentioned in the
thread.
To keep things a bit more simple, and streamline, I ended up pulling
out the logic for setting the startblock into another function, which
we only call once before the first call to
heap_parallelscan_nextpage(). I also ended up changing phs_cblock and
replacing it with a counter that always starts at zero. The actual
block is calculated based on that + the startblock modulo nblocks.
This makes things a good bit more simple for detecting when we've
allocated all the blocks to the workers, and also works nicely when
wrapping back to the start of a relation when we started somewhere in
the middle due to piggybacking with a synchronous scan.
Looks reasonable. I edited the comments and the variable names a bit, to
my liking, and committed. Thanks!
- Heikki
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