Re: [HACKERS] Cached plans and statement generalization

On 31.07.2019 19:56, Heikki Linnakangas wrote:
> On 09/07/2019 23:59, Konstantin Knizhnik wrote:
>> Fixed patch version of the path is attached.
>
> Much of the patch and the discussion has been around the raw parsing, 
> and guessing which literals are actually parameters that have been 
> inlined into the SQL text. Do we really need to do that, though? The 
> documentation mentions pgbouncer and other connection poolers, where 
> you don't have session state, as a use case for this. But such 
> connection poolers could and should still be using the extended query 
> protocol, with Parse+Bind messages and query parameters, even if they 
> don't use named prepared statements. I'd want to encourage 
> applications and middleware to use out-of-band query parameters, to 
> avoid SQL injection attacks, regardless of whether they use prepared 
> statements or cache query plans. So how about dropping all the raw 
> parse tree stuff, and doing the automatic caching of plans based on 
> the SQL string, somewhere in the exec_parse_message? Check the 
> autoprepare cache in exec_parse_message(), if it was an "unnamed" 
> prepared statement, i.e. if the prepared statement name is an empty 
> string.
>
> (I'm actually not sure if exec_parse/bind_message is the right place 
> for this, but I saw that your current patch did it in 
> exec_simple_query, and exec_parse/bind_message are the equivalent of 
> that for the extended query protocol).
>
> - Heikki

I decided to implement your proposal. Much simple version of autoprepare 
patch is attached.
At my computer I got the following results:

  pgbench -M simple -S         22495 TPS
  pgbench -M extended -S    47633 TPS
  pgbench -M prepared -S    47683 TPS


So autoprepare speedup execution of queries sent using extended protocol 
more than twice and it is almost the same as with explicitly prepared 
statements.
I failed to create regression test for it because I do not know how to 
force psql to use extended protocol. Any advice is welcome.

-- 
Konstantin Knizhnik
Postgres Professional: http://www.postgrespro.com
The Russian Postgres Company