Horton

Re: POC, WIP: OR-clause support for indexes

Nikolay Shaplov <dhyan@nataraj.su>

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From: Nikolay Shaplov <dhyan@nataraj.su>
To: Alexander Korotkov <aekorotkov@gmail.com>, pgsql-hackers@lists.postgresql.org
Cc: Andrei Lepikhov <a.lepikhov@postgrespro.ru>, jian he <jian.universality@gmail.com>, Robert Haas <robertmhaas@gmail.com>, pgsql-hackers@postgresql.org, Peter Geoghegan <pg@bowt.ie>, "Finnerty, Jim" <jfinnert@amazon.com>, Marcos Pegoraro <marcos@f10.com.br>, teodor@sigaev.ru, Tomas Vondra <tomas.vondra@enterprisedb.com>, Peter Eisentraut <peter@eisentraut.org>, Ranier Vilela <ranier.vf@gmail.com>, Alena Rybakina <a.rybakina@postgrespro.ru>
Date: 2024-06-24T20:51:56Z
Lists: pgsql-hackers

Commits

Same data as JSON: GET /api/v1/messages/:b64id/commits the thread's linked commits as JSON, with link sources. API reference →

  1. Make group_similar_or_args() reorder clause list as little as possible

  2. Allow usage of match_orclause_to_indexcol() for joins

  3. Skip not SOAP-supported indexes while transforming an OR clause into SAOP

  4. Remove the wrong assertion from match_orclause_to_indexcol()

  5. Teach bitmap path generation about transforming OR-clauses to SAOP's

  6. Transform OR-clauses to SAOP's during index matching

  7. Fix the value of or_to_any_transform_limit in postgresql.conf.sample

  8. Transform OR clauses to ANY expression

  9. MergeAttributes code deduplication

  10. SEARCH and CYCLE clauses

  11. Improve estimation of OR clauses using extended statistics.

  12. Teach btree to handle ScalarArrayOpExpr quals natively.

  13. Revise collation derivation method and expression-tree representation.

  14. Instead of trying to force WHERE clauses into CNF or DNF normal form,

Hi!

Let me join the review process.

I am no expert in execution plans, so there would not be much help in doing 
even better optimization. But I can read the code, as a person who is not 
familiar 
with this area and help making it clear even to a person like me.

So, I am reading v25-0001-Transform-OR-clauses-to-ANY-expression.patch that 
have been posted some time ago, and especially transform_or_to_any function.

> @@ -38,7 +45,6 @@
>  int			from_collapse_limit;
>  int			join_collapse_limit;
>
> - 
>  /*
>   * deconstruct_jointree requires multiple passes over the join tree,  
because we 
>   * need to finish computing JoinDomains before we start  distributing quals.

Do not think that removing empty line should be part of the patch

> +			/*
> +			 * If the const node's (right side of operator 
expression) type
> +			 * don't have “true” array type, then we cannnot 
do the
> +			 * transformation. We simply concatenate the 
expression node.
> +			 */
Guess using unicode double quotes is not the best idea here... 
   
Now to the first part of  `transform_or_to_any`:

> +	List	   *entries = NIL;
I guess the idea of entries should be explained from the start. What kind of 
entries are accomulated there... I see they are added there all around the 
code, but what is the purpose of that is not quite clear when you read it.

At the first part of `transform_or_to_any` function, you costanly repeat two 
lines, like a mantra:

> +			entries = lappend(entries, rinfo);
> +			continue;

"If something is wrong -- do that mantra"

From my perspective, if you have to repeat same code again and again, then 
most probably you have some issues with architecture of the code. If you 
repeat some code again and again, you need to try to rewrite the code, the 
way, that part is repeated only once.

In that case I would try to move the most of the first loop of 
`transform_or_to_any`  to a separate function (let's say its name is 
prepare_single_or), that will do all the checks, if this or is good for us; 
return NULL if it does not suits our purposes (and in this case we do "entries 
= lappend(entries, rinfo); continue" in the main code, but only once) or 
return pointer to some useful data if this or clause is good for our purposes. 

This, I guess will make that part more clear and easy to read, without 
repeating same "lappend mantra" again and again.

Will continue digging into the code tomorrow.

P.S. Sorry for sending partly finished email. Pressed Ctrl+Enter 
accidentally... With no way to make it back :-(((