public inbox for [email protected]
help / color / mirror / Atom feedFrom: Lakshmi N <[email protected]>
To: [email protected]
To: [email protected]
Subject: DOCS: pg_plan_advice minor doc fixes
Date: Wed, 8 Apr 2026 00:09:23 -0700
Message-ID: <CA+3i_M-mo7Of=Pn8WzRfJLt=fc=gDTn1oOdj8v8BEtgXh9ZMCg@mail.gmail.com> (raw)
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
Attachments:
[application/octet-stream] 0001-doc-Fix-pgplanadvice-tags-for-FOREIGN_JOIN-and-NESTE.patch (2.3K, 3-0001-doc-Fix-pgplanadvice-tags-for-FOREIGN_JOIN-and-NESTE.patch)
download | inline diff:
From a4d65b1f2eff505535097008f5ae55d0ae37d661 Mon Sep 17 00:00:00 2001
From: Lakshmi N <[email protected]>
Date: Tue, 7 Apr 2026 23:58:15 -0700
Subject: [PATCH] DOCS: Update pgplanadvice tags for FOREIGN_JOIN and
NESTED_LOOP_MEMOIZE
---
doc/src/sgml/pgplanadvice.sgml | 8 ++++----
1 file changed, 4 insertions(+), 4 deletions(-)
diff --git a/doc/src/sgml/pgplanadvice.sgml b/doc/src/sgml/pgplanadvice.sgml
index c3e1ccb60a2..73155461c0b 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>
@@ -288,10 +288,10 @@ 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
+ Specifying <literal>FOREIGN_JOIN</literal> for a single foreign table is
neither necessary nor permissible: a <literal>Foreign Scan</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
@@ -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>
--
2.43.0
view thread (4+ messages) latest in thread
reply
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Reply to all the recipients using the --to and --cc options:
reply via email
To: [email protected]
Cc: [email protected], [email protected]
Subject: Re: DOCS: pg_plan_advice minor doc fixes
In-Reply-To: <CA+3i_M-mo7Of=Pn8WzRfJLt=fc=gDTn1oOdj8v8BEtgXh9ZMCg@mail.gmail.com>
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
This inbox is served by agora; see mirroring instructions
for how to clone and mirror all data and code used for this inbox