Re: [HACKERS] Partition-wise join for join between (declaratively)partitioned tables - Mailing list pgsql-hackers

On Mon, Mar 13, 2017 at 3:24 PM, Robert Haas <robertmhaas@gmail.com> wrote:
> Haven't looked at 0007 yet.

+               if (rel->part_scheme)
+               {
+                       int             cnt_parts;
+
+                       for (cnt_parts = 0; cnt_parts < nparts; cnt_parts++)
+                       {
+                               if (rel->part_oids[cnt_parts] ==
childRTE->relid)
+                               {
+                                       Assert(!rel->part_rels[cnt_parts]);
+                                       rel->part_rels[cnt_parts] = childrel;
+                               }
+                       }
+               }

It's not very appealing to use an O(n^2) algorithm here.  I wonder if
we could arrange things so that inheritance expansion expands
partitions in the right order, and then we could just match them up
one-to-one.  This would probably require an alternate version of
find_all_inheritors() that expand_inherited_rtentry() would call only
for partitioned tables.  Failing that, another idea would be to use
qsort() or qsort_arg() to put the partitions in the right order.

+       if (relation->rd_rel->relkind != RELKIND_PARTITIONED_TABLE ||
+               !inhparent ||
+               !(rel->part_scheme = find_partition_scheme(root, relation)))

Maybe just don't call this function in the first place in the
!inhparent case, instead of passing down an argument that must always
be true.

+               /* Match the partition key types. */
+               for (cnt_pks = 0; cnt_pks < partnatts; cnt_pks++)
+               {
+                       /*
+                        * For types, it suffices to match the type
id, mod and collation;
+                        * len, byval and align are depedent on the first two.
+                        */
+                       if (part_key->partopfamily[cnt_pks] !=
part_scheme->partopfamily[cnt_pks] ||
+                               part_key->partopcintype[cnt_pks] !=
part_scheme->partopcintype[cnt_pks] ||
+                               part_key->parttypid[cnt_pks] !=
part_scheme->key_types[cnt_pks] ||
+                               part_key->parttypmod[cnt_pks] !=
part_scheme->key_typmods[cnt_pks] ||
+                               part_key->parttypcoll[cnt_pks] !=
part_scheme->key_collations[cnt_pks])
+                               break;
+               }

I think memcmp() might be better than a for-loop.

Overall this one looks pretty good and straightforward.  Of course, I
haven't looked at the main act (0009) yet.

-- 
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company