From de72d2a81a5911c7dcb5fb52ea489c94e336721f Mon Sep 17 00:00:00 2001
From: drh <drh@noemail.net>
Date: Mon, 3 Dec 2018 01:58:02 +0000
Subject: [PATCH] Remove two lines of unnecessary code, for a very small
 performance increase and size decrease.

FossilOrigin-Name: 15824ccda0f110794a479b58fbf36082d8c383f34bae9dc0921d96547fb37869
---
 manifest      | 12 ++++++------
 manifest.uuid |  2 +-
 src/pcache1.c |  9 ++++++---
 3 files changed, 13 insertions(+), 10 deletions(-)

diff --git a/manifest b/manifest
index 2d4789227a..2b309eede2 100644
--- a/manifest
+++ b/manifest
@@ -1,5 +1,5 @@
-C Fix\sa\sparser\sbug\sin\sthe\suse\sof\sparentheses\saround\stable-valued\sfunctions.
-D 2018-12-03T01:47:41.293
+C Remove\stwo\slines\sof\sunnecessary\scode,\sfor\sa\svery\ssmall\sperformance\sincrease\nand\ssize\sdecrease.
+D 2018-12-03T01:58:02.016
 F .fossil-settings/empty-dirs dbb81e8fc0401ac46a1491ab34a7f2c7c0452f2f06b54ebb845d024ca8283ef1
 F .fossil-settings/ignore-glob 35175cdfcf539b2318cb04a9901442804be81cd677d8b889fcc9149c21f239ea
 F Makefile.in a050c8670ea0d7b37b2192306cbb50d392acd9902b84e9b56f3444d006f97a6c
@@ -498,7 +498,7 @@ F src/pager.h 217921e81eb5fe455caa5cda96061959706bcdd29ddb57166198645ef7822ac3
 F src/parse.y 5cf85c2b9dfac38ac4e2bf2776484705186ce2eda8631e65cc0b04bf566c1173
 F src/pcache.c 696a01f1a6370c1b50a09c15972bc3bee3333f8fcd1f2da8e9a76b1b062c59ee
 F src/pcache.h 4f87acd914cef5016fae3030343540d75f5b85a1877eed1a2a19b9f284248586
-F src/pcache1.c bf9fcea656dce1cd2cca6b77a1d1d3552050d55a31c98bf0d9f405930a83bc95
+F src/pcache1.c ad0ffc5b35b0280d045ac569d34d4b842e3e6a4a118f6396b320987a0957afcc
 F src/pragma.c 4e056f042683b99c4ea0db395f68d051b1a95833ab40951c40d3ef7e1fee1354
 F src/pragma.h fdd03d78a7497f74a3f652909f945328480089189526841ae829ce7313d98d13
 F src/prepare.c f81f8d707e583192c28fea0b2e19385415b7d188123b23f49b038076408d7a69
@@ -1779,7 +1779,7 @@ F vsixtest/vsixtest.tcl 6a9a6ab600c25a91a7acc6293828957a386a8a93
 F vsixtest/vsixtest.vcxproj.data 2ed517e100c66dc455b492e1a33350c1b20fbcdc
 F vsixtest/vsixtest.vcxproj.filters 37e51ffedcdb064aad6ff33b6148725226cd608e
 F vsixtest/vsixtest_TemporaryKey.pfx e5b1b036facdb453873e7084e1cae9102ccc67a0
-P 5d933aa659eb7a13f9ab44fe7762be292a1c3c75b957a3b7e0bc6188257b62f4
-R 0af9de2350de25f0ebcc1d0eef1387db
+P 58a51123d1a6381cc67d3c64ba3468ec5a92c299ad6fd86de0b843d0ffafb846
+R a804252de7d9904d6bfbaabce768affa
 U drh
-Z 15852f1b01d70da9fb801cb007d16bf9
+Z e3cffb3b13ba67932ad3575ad4d1aeec
diff --git a/manifest.uuid b/manifest.uuid
index 1d5b14e4de..d71f9abd0c 100644
--- a/manifest.uuid
+++ b/manifest.uuid
@@ -1 +1 @@
-58a51123d1a6381cc67d3c64ba3468ec5a92c299ad6fd86de0b843d0ffafb846
\ No newline at end of file
+15824ccda0f110794a479b58fbf36082d8c383f34bae9dc0921d96547fb37869
\ No newline at end of file
diff --git a/src/pcache1.c b/src/pcache1.c
index 2880c2c5e6..6df0f15d13 100644
--- a/src/pcache1.c
+++ b/src/pcache1.c
@@ -102,6 +102,7 @@ struct PgHdr1 {
   PCache1 *pCache;               /* Cache that currently owns this page */
   PgHdr1 *pLruNext;              /* Next in LRU list of unpinned pages */
   PgHdr1 *pLruPrev;              /* Previous in LRU list of unpinned pages */
+                                 /* NB: pLruPrev is only valid if pLruNext!=0 */
 };
 
 /*
@@ -570,7 +571,8 @@ static PgHdr1 *pcache1PinPage(PgHdr1 *pPage){
   pPage->pLruPrev->pLruNext = pPage->pLruNext;
   pPage->pLruNext->pLruPrev = pPage->pLruPrev;
   pPage->pLruNext = 0;
-  pPage->pLruPrev = 0;
+  /* pPage->pLruPrev = 0;
+  ** No need to clear pLruPrev as it is never accessed if pLruNext is 0 */
   assert( pPage->isAnchor==0 );
   assert( pPage->pCache->pGroup->lru.isAnchor==1 );
   pPage->pCache->nRecyclable--;
@@ -908,8 +910,9 @@ static SQLITE_NOINLINE PgHdr1 *pcache1FetchStage2(
     pPage->iKey = iKey;
     pPage->pNext = pCache->apHash[h];
     pPage->pCache = pCache;
-    pPage->pLruPrev = 0;
     pPage->pLruNext = 0;
+    /* pPage->pLruPrev = 0;
+    ** No need to clear pLruPrev since it is not accessed when pLruNext==0 */
     *(void **)pPage->page.pExtra = 0;
     pCache->apHash[h] = pPage;
     if( iKey>pCache->iMaxKey ){
@@ -1069,7 +1072,7 @@ static void pcache1Unpin(
   /* It is an error to call this function if the page is already 
   ** part of the PGroup LRU list.
   */
-  assert( pPage->pLruPrev==0 && pPage->pLruNext==0 );
+  assert( pPage->pLruNext==0 );
   assert( PAGE_IS_PINNED(pPage) );
 
   if( reuseUnlikely || pGroup->nPurgeable>pGroup->nMaxPage ){