Re: [PATCH] Generic type subscription - Mailing list pgsql-hackers

Hi

Sorry for late reply and thank you for the feedback (especially about the

problem with performance).

> There is another occurrences of "subscription" including file names

Fixed.

> we have performance degradation of SELECT queries

Yes, I figured it out. The main problem was about type info lookups, some of

them were made for each data extraction operation, which is unnecessary.

Here are results on my machine:

with the fixed version of patch

=# explain analyze select a[1], b[1][1][1] from test;

                                                 QUERY PLAN                                                 

------------------------------------------------------------------------------------------------------------

 Seq Scan on test  (cost=0.00..5286.00 rows=100000 width=6) (actual time=0.950..48.370 rows=100000 loops=1)

 Planning time: 0.054 ms

 Execution time: 51.859 ms

(3 rows)

and without the patch

=# explain analyze select a[1], b[1][1][1] from test;                                                                                 

                                                 QUERY PLAN                                                 

------------------------------------------------------------------------------------------------------------

 Seq Scan on test  (cost=0.00..5286.00 rows=100000 width=6) (actual time=3.443..43.452 rows=100000 loops=1)

 Planning time: 0.117 ms

 Execution time: 46.875 ms

(3 rows)

It's still slightly slower because of all new logic aroung subscripting

operation, but not that much.