Re: [GSoC] Push-based query executor discussion

I have cleaned up the code a bit and added the separation I mentioned in
a previous mail -- now we there are even three functions instead of old
ExecProcNode: one for starting leaf nodes, one for passing tuples and
one for signaling that the node has finished its job. It is all
described in execProcnode.c.

I also rewrote HashJoin without using the explicit state machine. It
seems slightly cleaner to me now...

Here are updated benchmarks:
+-----+-----------+---------+----------+
|query|reversed, s|master, s|speedup, %|
+-----+-----------+---------+----------+
|q01  |108.21     |117.88   |8.94      |
+-----+-----------+---------+----------+
|q03  |55.48      |58.805   |5.99      |
+-----+-----------+---------+----------+
|q04  |78.405     |81.86    |4.41      |
+-----+-----------+---------+----------+
|q05  |49.91      |51.18    |2.54      |
+-----+-----------+---------+----------+
|q10  |49.215     |52.61    |6.9       |
+-----+-----------+---------+----------+
|q12  |63.24      |68.505   |8.33      |
+-----+-----------+---------+----------+
|q14  |33.42      |35.31    |5.66      |
+-----+-----------+---------+----------+

As before, 24 runs were performed, median taken, scale is 40GB,
postgresql.conf is the same.

Patches are rebased, now they apply on 4dd3abe99f50.


--
Arseny Sher