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gh-104144: Optimize gather to finish eagerly when all futures complete eagerly (#104138)

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Itamar Ostricher 2023-05-06 08:15:27 -07:00 • committed by GitHub
parent 96f95df48e
commit 263abd333d
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2 changed files with 15 additions and 1 deletions
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13
Lib/asyncio/tasks.py
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@ -813,6 +813,7 @@ def gather(*coros_or_futures, return_exceptions=False):
children = []
nfuts = 0
nfinished = 0
done_futs = []
loop = None
outer = None # bpo-46672
for arg in coros_or_futures:
@ -829,7 +830,10 @@ def gather(*coros_or_futures, return_exceptions=False):
nfuts += 1
arg_to_fut[arg] = fut
fut.add_done_callback(_done_callback)
if fut.done():
done_futs.append(fut)
else:
fut.add_done_callback(_done_callback)
else:
# There's a duplicate Future object in coros_or_futures.
@ -838,6 +842,13 @@ def gather(*coros_or_futures, return_exceptions=False):
children.append(fut)
outer = _GatheringFuture(children, loop=loop)
# Run done callbacks after GatheringFuture created so any post-processing
# can be performed at this point
# optimization: in the special case that *all* futures finished eagerly,
# this will effectively complete the gather eagerly, with the last
# callback setting the result (or exception) on outer before returning it
for fut in done_futs:
_done_callback(fut)
return outer