From ceacc29609058f7ba18288ac141e7c55a4f01382 Mon Sep 17 00:00:00 2001
From: Konstantin Knizhnik <knizhnik@garret.ru>
Date: Mon, 13 Jan 2025 16:26:11 +0200
Subject: [PATCH] Start with minimal prefetch distance to minimize prefetch
 overhead for exact or limited index scans (#10359)

## Problem

See https://neondb.slack.com/archives/C04DGM6SMTM/p1736526089437179

In case of queries index scan with LIMIT clause, multiple backends can
concurrently send larger number of duplicated prefetch requests which
are not stored in LFC and so actually do useless job.

Current implementation of index prefetch starts with maximal prefetch
distance (10 by default now) when there are no key bounds, so in queries
with LIMIT clause like `select * from T order by pk limit 1` compute can
send a lot of useless prefetch requests to page server.

## Summary of changes

Always start with minimal prefetch distance even if there are not key
boundaries.

Related Postgres PRs:
https://github.com/neondatabase/postgres/pull/552
https://github.com/neondatabase/postgres/pull/551
https://github.com/neondatabase/postgres/pull/550
https://github.com/neondatabase/postgres/pull/549

Co-authored-by: Konstantin Knizhnik <knizhnik@neon.tech>
---
 vendor/postgres-v14   | 2 +-
 vendor/postgres-v15   | 2 +-
 vendor/postgres-v16   | 2 +-
 vendor/postgres-v17   | 2 +-
 vendor/revisions.json | 8 ++++----
 5 files changed, 8 insertions(+), 8 deletions(-)

diff --git a/vendor/postgres-v14 b/vendor/postgres-v14
index c2f65b3201..210a0ba3af 160000
--- a/vendor/postgres-v14
+++ b/vendor/postgres-v14
@@ -1 +1 @@
-Subproject commit c2f65b3201591e02ce45b66731392f98d3388e73
+Subproject commit 210a0ba3afd8134ea910b203f274b165bd4f05d7
diff --git a/vendor/postgres-v15 b/vendor/postgres-v15
index f262d631ad..d3141e17a7 160000
--- a/vendor/postgres-v15
+++ b/vendor/postgres-v15
@@ -1 +1 @@
-Subproject commit f262d631ad477a1819e84a183e5a7ef561830085
+Subproject commit d3141e17a7155e3d07c8deba4a10c748a29ba1e6
diff --git a/vendor/postgres-v16 b/vendor/postgres-v16
index 97f9fde349..f63b141cfb 160000
--- a/vendor/postgres-v16
+++ b/vendor/postgres-v16
@@ -1 +1 @@
-Subproject commit 97f9fde349c6de6d573f5ce96db07eca60ce6185
+Subproject commit f63b141cfb0c813725a6b2574049565bff643018
diff --git a/vendor/postgres-v17 b/vendor/postgres-v17
index 7e3f3974bc..9c9e9a78a9 160000
--- a/vendor/postgres-v17
+++ b/vendor/postgres-v17
@@ -1 +1 @@
-Subproject commit 7e3f3974bc8895938308f94d0e96879ffae638cd
+Subproject commit 9c9e9a78a93aebec2f6a2f54644442d35ffa245c
diff --git a/vendor/revisions.json b/vendor/revisions.json
index bff2f70931..d182b88008 100644
--- a/vendor/revisions.json
+++ b/vendor/revisions.json
@@ -1,18 +1,18 @@
 {
   "v17": [
     "17.2",
-    "7e3f3974bc8895938308f94d0e96879ffae638cd"
+    "9c9e9a78a93aebec2f6a2f54644442d35ffa245c"
   ],
   "v16": [
     "16.6",
-    "97f9fde349c6de6d573f5ce96db07eca60ce6185"
+    "f63b141cfb0c813725a6b2574049565bff643018"
   ],
   "v15": [
     "15.10",
-    "f262d631ad477a1819e84a183e5a7ef561830085"
+    "d3141e17a7155e3d07c8deba4a10c748a29ba1e6"
   ],
   "v14": [
     "14.15",
-    "c2f65b3201591e02ce45b66731392f98d3388e73"
+    "210a0ba3afd8134ea910b203f274b165bd4f05d7"
   ]
 }