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help / color / mirror / Atom feedFrom: jie wang <[email protected]>
To: Lakshmi N <[email protected]>
Cc: [email protected]
Cc: [email protected]
Subject: Re: DOCS: pg_plan_advice minor doc fixes
Date: Wed, 8 Apr 2026 15:52:10 +0800
Message-ID: <CAJnZyeAdvzY01rTb_XDN3PfAPD0NZ61Ndf0J4j2H=GBTDVr5sQ@mail.gmail.com> (raw)
In-Reply-To: <CA+3i_M-mo7Of=Pn8WzRfJLt=fc=gDTn1oOdj8v8BEtgXh9ZMCg@mail.gmail.com>
References: <CA+3i_M-mo7Of=Pn8WzRfJLt=fc=gDTn1oOdj8v8BEtgXh9ZMCg@mail.gmail.com>
Lakshmi N <[email protected]> 于2026年4月8日周三 15:09写道：
> Hi hackers,
>
> I noticed the following minor discrepancy in the pg_plan_advice docs,
> attached a patch to address this.
>
> (1) FOREIGN SCAN should be FOREIGN JOIN in the scan method advice tag. I
> tested with FOREIGN SCAN and can confirm it gives a syntax error while the
> other one works correctly.
>
> postgres=# SET pg_plan_advice.advice = 'FOREIGN_JOIN((t1 t2))';
> EXPLAIN (COSTS OFF, PLAN_ADVICE)
> SELECT * FROM fdw_t1 t1 JOIN fdw_t2 t2 ON t1.id = t2.t1_id;
>
> SET
> QUERY PLAN
> -------------------------------------------------
> Foreign Scan
> Relations: (fdw_t1 t1) INNER JOIN (fdw_t2 t2)
> Supplied Plan Advice:
> FOREIGN_JOIN((t1 t2)) /* matched */
> Generated Plan Advice:
> FOREIGN_JOIN((t1 t2))
> NO_GATHER(t1 t2)
> (7 rows)
>
>
> (2) NESTED_LOOP_MEMOIZE is missing from the join method list in the doc
> though it is supported. Verified this by running below:
>
> postgres=# SET pg_plan_advice.advice = 'NESTED_LOOP_MEMOIZE(d)';
> SET
> postgres=# EXPLAIN (COSTS OFF, PLAN_ADVICE) select * from t1 f JOIN t2 ON
> f.id = t2.t1_id;
> QUERY PLAN
> --------------------------------------------
> Hash Join
> Hash Cond: (t2.t1_id = f.id)
> -> Seq Scan on t2
> -> Hash
> -> Seq Scan on t1 f
> Supplied Plan Advice:
> NESTED_LOOP_MEMOIZE(d) /* not matched */
> Generated Plan Advice:
> JOIN_ORDER(t2 f)
> HASH_JOIN(f)
> SEQ_SCAN(t2 f)
> NO_GATHER(f t2)
> (12 rows)
>
> Regards,
> Lakshmi
>
Hi,
I found that this patch is not fully modified and is missing a part:
`Foreign Scan` ---> `Foreign Join`
Best regards,
--
wang jie
Attachments:
[application/octet-stream] v2-0001-DOCS-Update-pgplanadvice-tags-for-FOREIGN_JOIN-an.patch (2.5K, 3-v2-0001-DOCS-Update-pgplanadvice-tags-for-FOREIGN_JOIN-an.patch)
download | inline diff:
From 83723bf0b96b043b849c747dc2dbb1c85a56f6f8 Mon Sep 17 00:00:00 2001
From: Lakshmi N <[email protected]>
Date: Tue, 7 Apr 2026 23:58:15 -0700
Subject: [PATCH v2] DOCS: Update pgplanadvice tags for FOREIGN_JOIN and
NESTED_LOOP_MEMOIZE
---
doc/src/sgml/pgplanadvice.sgml | 12 ++++++------
1 file changed, 6 insertions(+), 6 deletions(-)
diff --git a/doc/src/sgml/pgplanadvice.sgml b/doc/src/sgml/pgplanadvice.sgml
index c3e1ccb60a2..e8f5edec874 100644
--- a/doc/src/sgml/pgplanadvice.sgml
+++ b/doc/src/sgml/pgplanadvice.sgml
@@ -266,7 +266,7 @@ SEQ_SCAN(<replaceable>target</replaceable> [ ... ])
TID_SCAN(<replaceable>target</replaceable> [ ... ])
INDEX_SCAN(<replaceable>target</replaceable> <replaceable>index_name</replaceable> [ ... ])
INDEX_ONLY_SCAN(<replaceable>target</replaceable> <replaceable>index_name</replaceable> [ ... ])
-FOREIGN_SCAN((<replaceable>target</replaceable> [ ... ]) [ ... ])
+FOREIGN_JOIN((<replaceable>target</replaceable> [ ... ]) [ ... ])
BITMAP_HEAP_SCAN(<replaceable>target</replaceable> [ ... ])
DO_NOT_SCAN(<replaceable>target</replaceable> [ ... ])</synopsis>
@@ -288,11 +288,11 @@ DO_NOT_SCAN(<replaceable>target</replaceable> [ ... ])</synopsis>
</para>
<para>
- <literal>FOREIGN_SCAN</literal> specifies that a join between two or
+ <literal>FOREIGN_JOIN</literal> specifies that a join between two or
more foreign tables should be pushed down to a remote server so
- that it can be implemented as a single <literal>Foreign Scan</literal>.
- Specifying <literal>FOREIGN_SCAN</literal> for a single foreign table is
- neither necessary nor permissible: a <literal>Foreign Scan</literal> will
+ that it can be implemented as a single <literal>Foreign Join</literal>.
+ Specifying <literal>FOREIGN_JOIN</literal> for a single foreign table is
+ neither necessary nor permissible: a <literal>Foreign Join</literal> will
need to be used regardless. If you want to prevent a join from being
pushed down, consider using the <literal>JOIN_ORDER</literal> tag for
that purpose.
@@ -395,7 +395,7 @@ join_method_name(<replaceable>join_method_item</replaceable> [ ... ])
<phrase>where <replaceable>join_method_name</replaceable> is:</phrase>
-{ MERGE_JOIN_MATERIALIZE | MERGE_JOIN_PLAIN | NESTED_LOOP_MATERIALIZE | NESTED_LOOP_PLAIN | HASH_JOIN }
+{ MERGE_JOIN_MATERIALIZE | MERGE_JOIN_PLAIN | NESTED_LOOP_MATERIALIZE | NESTED_LOOP_MEMOIZE | NESTED_LOOP_PLAIN | HASH_JOIN }
<phrase>and <replaceable>join_method_item</replaceable> is:</phrase>
--
2.34.1
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Subject: Re: DOCS: pg_plan_advice minor doc fixes
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