Re: speeding up planning with partitions

On Fri, Sep 14, 2018 at 3:58 PM, Amit Langote
<Langote_Amit_f8@lab.ntt.co.jp> wrote:
> Thanks a lot for your detailed review.
>
I was going through your patch (v3-0002) and I have some suggestions

1.
- if (nparts > 0)
+ /*
+ * For partitioned tables, we just allocate space for RelOptInfo's.
+ * pointers for all partitions and copy the partition OIDs from the
+ * relcache.  Actual RelOptInfo is built for a partition only if it is
+ * not pruned.
+ */
+ if (rte->relkind == RELKIND_PARTITIONED_TABLE)
+ {
  rel->part_rels = (RelOptInfo **)
- palloc(sizeof(RelOptInfo *) * nparts);
+ palloc0(sizeof(RelOptInfo *) * rel->nparts);
+ return rel;
+ }

I think we can delay allocating memory for rel->part_rels?  And we can
allocate in add_rel_partitions_to_query only
for those partitions which survive pruning.

2.
add_rel_partitions_to_query
...
+ /* Expand the PlannerInfo arrays to hold new partition objects. */
+ num_added_parts = scan_all_parts ? rel->nparts :
+ bms_num_members(partindexes);
+ new_size = root->simple_rel_array_size + num_added_parts;
+ root->simple_rte_array = (RangeTblEntry **)
+ repalloc(root->simple_rte_array,
+ sizeof(RangeTblEntry *) * new_size);
+ root->simple_rel_array = (RelOptInfo **)
+ repalloc(root->simple_rel_array,
+ sizeof(RelOptInfo *) * new_size);
+ if (root->append_rel_array)
+ root->append_rel_array = (AppendRelInfo **)
+ repalloc(root->append_rel_array,
+ sizeof(AppendRelInfo *) * new_size);
+ else
+ root->append_rel_array = (AppendRelInfo **)
+ palloc0(sizeof(AppendRelInfo *) *
+ new_size);

Instead of re-pallocing for every partitioned relation can't we first
count the total number of surviving partitions and
repalloc at once.

3.
+ /*
+ * And do prunin.  Note that this adds AppendRelInfo's of only the
+ * partitions that are not pruned.
+ */

prunin/pruning

-- 
Regards,
Dilip Kumar
EnterpriseDB: http://www.enterprisedb.com