Hi Dilip, Thanks for looking at the patch.
On 2017/09/15 13:43, Dilip Kumar wrote: > On Wed, Sep 6, 2017 at 4:08 PM, Amit Langote >> [PATCH 2/5] WIP: planner-side changes for partition-pruning >> >> This patch adds a stub get_partitions_for_keys in partition.c with a >> suitable interface for the caller to pass bounding keys extracted from the >> query and other related information. >> >> Importantly, it implements the logic within the planner to match query's >> scan keys to a parent table's partition key and form the bounding keys >> that will be passed to partition.c to compute the list of partitions that >> satisfy those bounds. > > + Node *leftop = get_leftop(clause); > + > + if (IsA(leftop, RelabelType)) > + leftop = (Node *) ((RelabelType *) leftop)->arg; > + > + if (equal(leftop, partkey)) > > It appears that this patch always assume that clause will be of form > "var op const", but it can also be "const op var" > > That's the reason in below example where in both the queries condition > is same it can only prune in the first case but not in the second. > > postgres=# explain select * from t where t.a < 2; > QUERY PLAN > -------------------------------------------------------- > Append (cost=0.00..2.24 rows=1 width=8) > -> Seq Scan on t1 (cost=0.00..2.24 rows=1 width=8) > Filter: (a < 2) > (3 rows) > > postgres=# explain select * from t where 2>t.a; > QUERY PLAN > -------------------------------------------------------- > Append (cost=0.00..4.49 rows=2 width=8) > -> Seq Scan on t1 (cost=0.00..2.24 rows=1 width=8) > Filter: (2 > a) > -> Seq Scan on t2 (cost=0.00..2.25 rows=1 width=8) > Filter: (2 > a) > (5 rows) Yeah, there are a bunch of smarts still missing in that patch as it is. Thanks, Amit -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
