On Sat, Oct 29, 2016 at 12:17 PM, Dilip Kumar <dilipbalaut@gmail.com> wrote:
> What about putting slot reference inside HeapScanDesc ?. I know it
> will make ,heap layer use executor structure but just a thought.
>
> I have quickly hacked this way where we use slot reference in
> HeapScanDesc and directly use
> slot_getattr inside HeapKeyTest (only if we have valid slot otherwise
> use _heap_getattr) and measure the worst case performance (what you
> have mentioned above.)
>
> My Test: (21 column table with varchar in beginning + qual is on last
> few column + varying selectivity )
>
> postgres=# \d test
> Table "public.test"
> Column | Type | Modifiers
> --------+-------------------+-----------
> f1 | integer |
> f2 | character varying |
> f3 | integer |
> f4 | integer |
> f5 | integer |
> f6 | integer |
> f7 | integer |
> f8 | integer |
> f9 | integer |
> f10 | integer |
> f11 | integer |
> f12 | integer |
> f13 | integer |
> f14 | integer |
> f15 | integer |
> f16 | integer |
> f17 | integer |
> f18 | integer |
> f19 | integer |
> f20 | integer |
> f21 | integer |
>
> tuple count : 10000000 (10 Million)
> explain analyze select * from test where f21< $1 and f20 < $1 and f19
> < $1 and f15 < $1 and f10 < $1; ($1 vary from 1Million to 1Million).
>
> Target code base:
> -----------------------
> 1. Head
> 2. Heap_scankey_pushdown_v1
> 3. My hack for keeping slot reference in HeapScanDesc
> (v1+use_slot_in_HeapKeyTest)
>
> Result:
> Selectivity Head scan_key_pushdown_v1 v1+use_slot_in_HeapKeyTest
> 0.1 3880 2980 2747
> 0.2 4041 3187 2914
> 0.5 5051 4921 3626
> 0.8 5378 7296 3879
> 1.0 6161 8525 4575
>
> Performance graph is attached in the mail..
>
> Observation:
> ----------------
> 1. Heap_scankey_pushdown_v1, start degrading after very high
> selectivity (this behaviour is only visible if table have 20 or more
> columns, I tested with 10 columns but with that I did not see any
> regression in v1).
>
> 2. (v1+use_slot_in_HeapKeyTest) is always winner, even at very high selectivity.
The patch is attached for this (storing slot reference in HeapScanDesc)..
--
Regards,
Dilip Kumar
EnterpriseDB: http://www.enterprisedb.com