Horton

RE: Hybrid Hash/Nested Loop joins and caching results from subplans

Zhijie Hou (Fujitsu) <houzj.fnst@fujitsu.com>

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From: "houzj.fnst@fujitsu.com" <houzj.fnst@fujitsu.com>
To: David Rowley <dgrowleyml@gmail.com>
Cc: PostgreSQL Developers <pgsql-hackers@lists.postgresql.org>, Andres Freund <andres@anarazel.de>, Andy Fan <zhihui.fan1213@gmail.com>, Alvaro Herrera <alvherre@alvh.no-ip.org>, Tom Lane <tgl@sss.pgh.pa.us>, Zhihong Yu <zyu@yugabyte.com>
Date: 2021-04-01T10:41:30Z
Lists: pgsql-hackers 
> I've attached the updated patch.  I'll let the CFbot grab this to ensure it's
> happy with it before I go looking to push it again.

Hi,

I took a look into the patch and noticed some minor things.

1.
+		case T_ResultCache:
+			ptype = "ResultCache";
+			subpath = ((ResultCachePath *) path)->subpath;
+			break;
 		case T_UniquePath:
 			ptype = "Unique";
 			subpath = ((UniquePath *) path)->subpath;
should we use "case T_ResultCachePath" here?

2.
Is it better to add ResultCache's info to " src/backend/optimizer/README " ?
Something like:
  NestPath      - nested-loop joins
  MergePath     - merge joins
  HashPath      - hash joins
+ ResultCachePath - Result cache

Best regards,
Hou zhijie

Commits

  1. Add Result Cache executor node (take 2)

  2. Add Result Cache executor node

  3. Allow estimate_num_groups() to pass back further details about the estimation

  4. Allow users of simplehash.h to perform direct deletions

  5. Cache if PathTarget and RestrictInfos contain volatile functions

  6. Fix pull_varnos' miscomputation of relids set for a PlaceHolderVar.