postgres

Author SHA1 Message Date

Author	SHA1	Message	Date
Robert Haas	bfc78d7196	Rewrite interaction of parallel mode with parallel executor support. In the previous coding, before returning from ExecutorRun, we'd shut down all parallel workers. This was dead wrong if ExecutorRun was called with a non-zero tuple count; it had the effect of truncating the query output. To fix, give ExecutePlan control over whether to enter parallel mode, and have it refuse to do so if the tuple count is non-zero. Rewrite the Gather logic so that it can cope with being called outside parallel mode. Commit `7aea8e4f2d` is largely to blame for this problem, though this patch modifies some subsequently-committed code which relied on the guarantees it purported to make.	10 years ago
Tom Lane	bf686796a0	Add missing "static" specifier. Per buildfarm (pademelon, at least, doesn't like this).	10 years ago
Robert Haas	3bd909b220	Add a Gather executor node. A Gather executor node runs any number of copies of a plan in an equal number of workers and merges all of the results into a single tuple stream. It can also run the plan itself, if the workers are unavailable or haven't started up yet. It is intended to work with the Partial Seq Scan node which will be added in future commits. It could also be used to implement parallel query of a different sort by itself, without help from Partial Seq Scan, if the single_copy mode is used. In that mode, a worker executes the plan, and the parallel leader does not, merely collecting the worker's results. So, a Gather node could be inserted into a plan to split the execution of that plan across two processes. Nested Gather nodes aren't currently supported, but we might want to add support for that in the future. There's nothing in the planner to actually generate Gather nodes yet, so it's not quite time to break out the champagne. But we're getting close. Amit Kapila. Some designs suggestions were provided by me, and I also reviewed the patch. Single-copy mode, documentation, and other minor changes also by me.	10 years ago

Robert Haas

Rewrite interaction of parallel mode with parallel executor support.

In the previous coding, before returning from ExecutorRun, we'd shut
down all parallel workers.  This was dead wrong if ExecutorRun was
called with a non-zero tuple count; it had the effect of truncating
the query output.  To fix, give ExecutePlan control over whether to
enter parallel mode, and have it refuse to do so if the tuple count
is non-zero.  Rewrite the Gather logic so that it can cope with being
called outside parallel mode.

Commit 7aea8e4f2d is largely to blame
for this problem, though this patch modifies some subsequently-committed
code which relied on the guarantees it purported to make.

10 years ago

Tom Lane

bf686796a0

Add missing "static" specifier.

Per buildfarm (pademelon, at least, doesn't like this).

10 years ago

Robert Haas

3bd909b220

Add a Gather executor node.

A Gather executor node runs any number of copies of a plan in an equal
number of workers and merges all of the results into a single tuple
stream.  It can also run the plan itself, if the workers are
unavailable or haven't started up yet.  It is intended to work with
the Partial Seq Scan node which will be added in future commits.

It could also be used to implement parallel query of a different sort
by itself, without help from Partial Seq Scan, if the single_copy mode
is used.  In that mode, a worker executes the plan, and the parallel
leader does not, merely collecting the worker's results.  So, a Gather
node could be inserted into a plan to split the execution of that plan
across two processes.  Nested Gather nodes aren't currently supported,
but we might want to add support for that in the future.

There's nothing in the planner to actually generate Gather nodes yet,
so it's not quite time to break out the champagne.  But we're getting
close.

Amit Kapila.  Some designs suggestions were provided by me, and I also
reviewed the patch.  Single-copy mode, documentation, and other minor
changes also by me.

10 years ago

3 Commits (e4a618aa1ec420f40198e89ef1afd7a4e8cfcecf)